125 RACE REPLICA APRILIA RS125 / CAGIVA MITO 125

FREE aprilia rs125 workshop manuals

2012-04-26T04:48:00.001-07:00

THE APRILIA RS125 MANUAL
http://dl.dropbox.com/u/69508806/BLOG%20MANUAL/Aprilia_RS125_Workshop_Manual-part1.pdf
part 1
http://dl.dropbox.com/u/69508806/BLOG%20MANUAL/Aprilia_RS125_Workshop_Manual-part2.pdf
part 2
http://dl.dropbox.com/u/69508806/BLOG%20MANUAL/Aprilia_RS125_Workshop_Manual-part3.pdf
part 3

ROTAX 122 ENGINE MANUAL (98on rs125s)

http://dl.dropbox.com/u/69508806/BLOG%20MANUAL/Aprilia_Rotax_Engine_Manual_122.pdf

DELLORTO CARB TUNING / SET UP / JETTING MANUAL

http://dl.dropbox.com/u/69508806/BLOG%20MANUAL/DellortoCarbTuning.pdf

aprilia rs 125 engine removal / top end removal

2012-04-26T03:53:00.002-07:00

aprilia rs125 rotax 122 engine removal

122 rotax engine removal pictorial (video )

http://www.youtube.com/watch?v=ItPehjy5p9A

top end removal pictorial (video)

http://www.youtube.com/watch?v=1UZ12cVM7D8

carbs / jetting rs125 aprilia

2012-04-20T15:19:00.001-07:00

How to Jet

Mark your throttle housing and grip in 1/4 turn increments. Use a marker, razor blade, etc.

Now get the motor to operating temperature by riding around.

Once the motor is warm, ride in 2nd and 3rd gear from the low RPM to high RPM. This puts a good load on the motor and is an accurate test of performance. Try to notice if the problem gets worse or better as the motor heats up.

Now try to locate the throttle opening at which the problem exists. See details just below.

plug chops are the key to fine tuning the main jet once the other circuits are set:

White to Porcelain / Chocolate / Mocha Brown to Black-Wet

Lean / Perfect! / Rich

A plug chop simply means looking at the sparkplug to determine how you are jetted at a particular throttle stage. The only tricky part is in isolating the throttle stage. Before starting, clean your sparkplug and filter and warm the bike up.

To check the main jet, which operates from 1/2 to full throttle, get the scooter up to a steady full throttle or near to it for a good few seconds, then simultaneously pull in the clutch and kill the engine. Don't let the motor drag you to a stop, or fall to an idle, because you want to isolate the plug color at full throttle.

Get off and check the sparkplug color. (Links on our tech page.) It should be a light chocolate color. If it's white, the air/fuel mixture is too lean and you need a bigger main jet. If it's black or really dark brown, the air/fuel mixture is too rich and a smaller main jet is needed. If you need to change jets, change by one size, and do another run.

Rich Jetting Symptoms and Solutions

Motor won't idle and idle set screw is ineffective. Try leaning out the air screw by turning it counter clockwise a quarter turn at a time. If the air screw has no effect, install a leaner pilot jet and return the air screw to 1 turn out. Proper air screw settings are usually between 1 and 2 1/2 turns out. The correct pilot for your bike is one that allows instant off-idle throttle response, and allows the air screw to be effective between 1 and 2.5 turns out. If the problem still exists, check and clean the choke circuit and carb vent lines.

Motor stumbles off idle to 1/2 throttle, then cleans up. If everything in part A above is correct, check the needle. Stock position is usually in the middle, but check your owner's manual to be sure. To lean out the needle, you need to raise the clip. If the needle is dropped all the way lean and problem still exists, try a leaner needle.

Motor will rev through the mid range then becomes gurgley (technical term) at full throttle and power is sluggish. This is a text book example of a rich main jet. This problem often occurs when an air filter becomes clogged and gets worse as the motor heats up. Choose a main jet with a smaller number and lean out the air fuel mixture one step at a time. If the problem still persists even though it's improved a little, reinstall your original main jet and lean out the needle one position. Now fine tune the main jet with plug checks.

Lean Jetting Symptoms and Solutions

Motor hesitates off idle with a "Boooooooooowang" sound. This is a lean symptom and often occurs when a motor is cold. Try turning the air-fuel screw clockwise a quarter turn richer and check throttle response again until motor revs without hesitation. If the motor "hangs up" or doesn't come right back down to idle, install a richer pilot, and reset air screw.

Motor knock knock knocks at idle when hot. Try solution A. If problem persists, perform a "leakdown pressure test" to check for ignition crank seal leakage.

Motor revs clean and crisp but runs really hot and lacks power. This symptom indicates a lean main jet and/or needle. Use a richer main jet and/or needle setting. This is the most common misconception about two stroke jetting: When a motor runs excessively hot and lacks power, it is on the verge of seizing. If you are on the trail and don't have the right main jet, try raising the needle by lowering the clip. It won't be exact but at least you won't seize.

Note: To be certain that your problem is lean, pull on the choke and see if the problem gets better or worse. If better, your problem is a lean condition.

Keihin Carburetion Jetting

AIR SCREW:

The air screw is a small (5mm in diameter) slotted brass adjustment screw located on the inlet side (air filter side) of the carburetor. The airscrew is a fine-tuning adjustment designed to allow the carburetor to be slightly adjusted for variances in atmospheric conditions. The airscrew works with the pilot/slow speed system of the carburetor, mainly affecting the engines initial starting, idling and initial power delivery. Proper adjustment of the airscrew can offer direct feed back on the necessary setting required for the pilot jet. The airscrew is adjusted in a rather straightforward manor.

The ideal procedure for setting the screw in the correct position is to warm up your ATV engine to the proper operating temperature. Then turn the idle up so it is idling about 500 RPM’s higher than normal. Next turn the airscrew all the way in until it bottoms out, once bottomed out slowly back the screw out a ¼ turn at a time (give the engine 10-15 seconds between each ¼ turn of the screw, to allow the engine to catch up with the adjustments). Continue backing the airscrew out until the engine idles at its highest RPM. The preferred setting window is between 1 and 2 turns. If the engine idles at its highest RPM from 0-1 turns out this means the pilot setting is on the Lean side and a larger pilot jet should be installed. If the engine idles at its highest RPM at over 2 turns out, this means the pilot setting is on the Rich side and a smaller pilot jet should be installed.

If you get no RPM fluctuation when adjusting the air screw there is a very realistic chance that there is something clogging the pilot/slow speed system. Clean the system thoroughly with contact cleaner and blow out with compressed air. Carburetor must be disassembled.

If the airscrew adjustment process is unsuccessful and leaves you confused. Set the screw at 1 ½ turns out and consult a professional for further assistance.

PILOT JET:

The pilot jet is a medium size (¾-1”) brass jet located inside the float bowl next to the needle jet/main jet location. The pilot jet meters the fuel required for engine starting, idling and the initial throttle opening 0-1/8.

A lean pilot jet setting will cause your engine to surge at very low RPM’s, bog or cut-out when the throttle is opened quickly and have trouble idling down.

A rich pilot setting will result in hard starting, plug fouling at low RPM’s, sputtering as the throttle is cracked opened.

The pilot jet is not difficult to set. With proper air screw adjustment and a close initial setting from your engine tuner, fine-tuning should be painless. Once set the pilot jet is not terribly sensitive. You should only be required to adjust the setting when confronted with large weather changes or altitude swings of over 2000 ft.

If adjusting the pilot jet gives inconsistent feed back, or does unexplainable things. Check and clean out the pilot/slow speed system thoroughly with contact cleaner and blow out with compressed air.

SLIDE:

The slide not only monitors how much airflow goes into your engine (its main job). But it has various angles cut on the bottom of the slide to monitor airflow at low RPM’s. This is referred to as slide cut away. The slide cut away is measured in 4.0, 5.0, 6.0 etc. (see attached chart). The higher the number, the larger the cut away the leaner the slide setting is.

The slide cut away generally effects the jetting in the ¼ throttle range at almost the same throttle position as the needle diameter effects. The slide cut away is usually predetermined by the engine manufacture or engine tuner. As a general rule do not change the slide cut away unless instructed to do so by a skilled engine tuner.

For ¼ throttle jetting adjustments it is easier to adjust the needle diameter.

NEEDLE:

The jet needle is the most important component in determining your carburetors jetting. The needle is broken into 3 main functions; Diameter, Length, Taper. These needle functions have a large effect on the carburetors jetting from ¼ to ¾ throttle. In the following paragraphs we will explain the needles functions and how to adjust them.

DIAMETER: The needle diameter controls the jetting just above the pilot jet, right as the engine begins to pull. On most engine combinations the needle diameter is felt in the ¼ throttle range. The setting of the needle diameter is crucial to both the engines low RPM power and reliability.

The jetting at ¼ throttle is adjusted by changing the diameter of the needle. On gold colored needles identified with the 3 stamped in letter I.D. system the last letter refers to the needle diameter size. By referencing the enclosed jetting chart you can verify your needles size, and be able to determine what needle size may be required for your specific situation. In many instances you can leave the taper and length settings the same (if they are correct) and adjust only the diameter. EXAMPLE: If you have a needle marked DGJ and change it for a needle marked DGK, you have effectively Leaned the jetting at the ¼ throttle position. Reference the enclosed jetting chart to clearly understand this adjustment.

When the needle diameter is Lean the machine will have a loss of low-end power. The engine will feel very zingy (like a 125cc engine). When an engine is in this condition and then put under a heavy load the engine becomes very susceptible to seizing.

When the needle diameter is Rich the machine will sputter at ¼ throttle and be hesitant to take the throttle. In extreme cases the engine can feel like the choke is on or the plug is fouling.

When the needle diameter jetting is set correctly the engine will accelerate evenly thru the first part of the power band. The proper diameter setting will provide maximum low RPM power and very ride able throttle response.

It is important to remember that even though the needle diameter is mainly responsible for the jetting at ¼ throttle there is some bleed effect. With experience this can easily be deciphered. An excellent way to pin point the feel of the needle diameter is test needles in your machine that have both the same taper and length but richer and leaner diameter settings. Try a needle of each setting in your machine for 10-15 minutes of riding and you will begin to understand specifically what throttle position your dealing with.

LENGTH: The needle length is determined by the clip position (grooves at top of needle) setting on the upper portion of the needle. On most needles there are 5 clip positions. The top clip position is referred to as #1 and is the Leanest setting. The clips are referred to in numerical order with the bottom position being #5, the Richest (refer to attached jetting chart illustration). The clip/length setting covers the largest percentage of jetting in your carburetor. With an emphasis at ½ throttle, the clip (length) setting will bleed both up and down to some degree to cover a wide portion of the midrange jetting.

When the clip/length setting is Lean the machine will be very zingy sounding and feel kind of similar to an 80cc or 125cc machine. Lean in the midrange will also rob power and cause the machine to run hot and seize easily

When the clip/length setting is Rich the machine will have a lazy feeling in the midrange. Exhaust note will be a little flat sounding. In extreme cases of richness the engine will even sputter or kind of crap out in the midrange.

The safest way to set the clip position is to richen up the clip position setting until the machine loses a little power (feels lazy/unresponsive) then lean it back one position. Ideally you like to run the needle setting in either the 3rd or 4th clip position, if possible. The needle clip jetting is especially critical to your machines reliability because on average more time is spent in the midrange than any other part of the throttle. Most machines pull very hard in the midrange, putting quite a load on the engine. This makes a lean condition very detrimental to your reliability.

TAPER: The needle taper is the angle of the needle at its lower half. The taper works the transition between the midrange and full throttle/main jet (¾ throttle position). The taper is the least sensitive function of the needle. Changes in the taper have very mild subtle changes in the jetting. The taper also affects the main jet size your carburetor requires. A leaner needle taper will use a richer main jet than a comparable engine/carburetor combo with a richer needle taper.

As a general rule, your engine tuner or engine manufacture should preset the taper. Once set correctly by a professional the taper setting should not need to be changed except for cases of extreme temperature reduction.

MAIN JET:

The main jet affects the jetting in the upper quarter of the throttle position. Coming into play at ¾ throttle on through to full open throttle. Even though most people relate the main jet to their carburetor in general. The main jet is only responsible for the last ¼ of the jetting. The main jet does not effect the jetting for starting and idling. It plays no part on low RPM or mid RPM jetting either. The main jet is very important to your machines overall tuning, but should never be over emphasized at the expense of needle tuning or other facets of your carburetion tuning.

When the main jet is Lean the engine will experience detonation or “pinging”. Exhaust note will be of a higher, tinier type note. Engine will over heat easy and can be down on horsepower. A moderately lean main jet can cause engine seizures. A severely lean main jet can cause the engine to burn a piston (whole in top).

When the main jet is Rich the engine will be a bit flat or lazy at ¾ to full throttle, giving off a flat, dead sounding exhaust note. When the main jet is severely rich the engine will sputter in the high RPM’s and have a lot of trouble making power up top.

The safest way to get the main jet setting as near correct as possible is to richen the main jet setting up until the engine begins to lose power and not rev to as high of RPM as before. On a single cylinder machine this will signal that the jetting is beginning to get rich. Depending on your riding application you can lean it down a bit from there or leave it for conditions requiring extra fuel (desert racing, long high speed runs, etc.)

As a general rule, richen the jetting up as long as the engine likes it and continues to run just as well or better than the smaller size main jet previously installed. When the engine no longer continues to improve its performance you will know you have gone to far.

JETTING: Getting the most out of your bike

I have had a lot of questions in reference to my article on carburetor jetting, so I have simplified the procedures to elevate as many questions as possible.

For whatever reason it becomes necessary to re-jet a carburetor, it is without a doubt a nightmare if you do not have a procedure to follow. The following is nothing more than a technique, procedure, steps or whatever you want to call it to help identify and isolate the carburetor circuit involved.

You can only begin re-jetting your carburetor if the following conditions are met:

Top end is in good condition.

Bottom end is in good condition. Crank seals.

Spark plugs, air filters, reeds and so on.

If your bike's motor is not mechanically sound, then all the jetting in the world will not help. With all of the above conditions met, you should be able to jet your carburetor following these steps:

Step 1: DETERMINE THE CORRECT NEEDLE AND OR NEEDLE JET.

Whether or not your carburetor is a MIKUNI or a KEIHIN, it does not matter. This is the most important step in jetting your carburetor--period!

Remove the main jet.

Place needle clip in mid-position.

Start motor and run it on the stand.

Condition: Motor running and main jet out. Needle or needle jet is correct: Carburetor should run clean to approximately 3/4 throttle. From 3/4 throttle to full throttle, the motor should start to break up as a result of too rich condition.

Correction: None needed.

Condition: Needle or needle jet is too rich. Carburetor runs clean to approximately 1/2 throttle but breaks up before 3/4 throttle as a result of too rich condition.

Correction: Mikuni replace needle jet with next leaner and test again. Keihin replace needle with next leaner diameter and test again.

Condition: Needle or needle jet is too lean: Carburetor runs clean beyond 3/4 throttle and has an erratic throttle response.

Correction: Mikuni replace needle jet with next richer and test again. Keihin replace needle with next richer diameter and test again.

The emphasis here is to find the correct needle or needle jet diameter, which will allow more fuel to pass than is needed but not so much that the needle itself has no control below 3/4 throttle.

Step 2: DETERMINE THE CORRECT PILOT JET.

Make sure the bike is warmed up if at all possible.

Main jet out.

Needle clip in mid position.

Turn air screw all the way in then 1/4 turn out.

Start motor and run it on the stand.

Adjust idle so the bike will just barely idle.

Condition: Motor running and main jet out.

PILOT JET CORRECT: With one hand on the throttle maintaining RPM at approximately 1/8 throttle, turn air screw 1/4 turn at a time clock wise until you bottom it out. Motor should become slightly erratic and you should have to play with throttle to maintain RPM. Start turning air screw counter clock wise, 1/4 turn at a time until you have reached 2 3/4 turns out. Between 1 1/4 and 2 1/4 turns, your motor should have reached its highest RPM maintaining a steady throttle. Adjust air screw again between 1 1/4 and 2 1/4 until you have determined highest RPM. Quick throttle response should be clean without bog.

PILOT JET TO RICH:

RPM does not reach a peak between 1 1/4 and 2 1/4 turns, stays the same or keeps rising out to 2 3/4 turns.

Correction: Mikuni replace pilot jet with next leaner and test again. Keihin replace pilot jet with next leaner and test again.

PILOT JET TO LEAN:

RPM does not become erratic and motor maintains throttle when air screw is turned all the way clockwise.

Correction: Mikuni replace pilot jet with next richer and test again. Keihin replace pilot jet with next richer and test again. Remember, with a steady throttle approximately 1/8, there should be a distinct difference in RPM from 1 1/4 turns to 2 1/4 turns if the pilot jet is correct. The emphasis here is to find a pilot jet that will run crisp without bog and without the main jet.

Step 3: DETERMINE THE CORRECT MAIN JET.

The main jet selection process is easy once you have the correct needle diameter or needle jet. You now only have to correct a rich condition from 3/4 throttle on up and you know what a rich condition sounds like. Your pilot circuit is correct and without bog.

Replace main jet with one that is at least two sizes smaller.

Needle clip in mid position.

Start motor and run it on the stand.

By replacing the main jet with one that is too small, you are looking for a condition that is too lean. You adjust your main jet from a too small to lean condition.

Condition: Motor running and main jet in.

MAIN JET CORRECT:

Carburetor should run clean and crisp to full throttle.

Correction: None needed.

MAIN JET TOO RICH:

RPM reaches a peak slowly with a deep sound. Excess fuel and oil mixture at end of silencer. Spark plug fowls easily and is dark in color.

Correction: Mikuni replace main jet with next leaner and test again. Keihin replace main jet with next leaner and test again.

MAIN JET TOO LEAN:

RPM reaches a peak quickly but erratic. A quick full snap open of throttle causes the motor to hesitate BEWAH sound or a complete bog. Motor sounds like it has a ring to it. End of silencer white. Spark plug is white in color.

Correction: Mikuni replace main jet with next richer until the BEWAH bog just barely goes away, then replace the main jet with the next richer and run it. Keihin replace main jet with next richer until the BEWAH bog just barely goes away, then replace the main jet with the next richer and run it. The emphasis here is find a main jet that is just rich enough to allow you snap the throttle wide open without the motor bogging as a result of the main being too lean. Should be a quick crisp throttle with no hesitation.

Step 4: DETERMINE THE CORRECT NEEDLE TAPER AND CUT AWAY.

This step in the jetting process can be made very simple if you remain close to stock. However, your needle taper is adjusted for 1/2 throttle to 3/4 throttle. Start off with a rich taper (shallow taper angle) and keep going leaner (steeper taper angle) until it will not maintain constant RPM at 1/2 throttle (runs erratic). Go back to the leanest taper angle that ran the smoothest at 1/2 to 3/4 throttle and that should be the correct taper.

The needle taper final test should be under track conditions with the greatest effect entering and exiting corners. Do not change the needle diameter or needle jet size during this process because that has already been determined. Adjust taper and throttle cut away only.

Throttle cut away effects from idle to 1/4 throttle. The correct cut away will maintain steady 1/8 throttle with quick throttle response. Generally the stock cut away is very close. Experiment with different cut away until it maintains the best response to 1/4 throttle.

That's it, if you spend the time jetting correctly, the benefits you will gain definitely out-weigh way the time spent. Take the guesswork out jetting by following a procedure that has been given or one you have laid out yourself. Keep the black magic process out of your tuning tricks and you will be better off for it.

From an article by Don K. Courtney. Link is dead now.

Jetting Tip: pilot jet and air screw

To check to see if your pilot jet and air screw are adjusted right, warm up the motor and let it idle as low as possible while still running smooth. From idle, whack the throttle wide open then let it close completely. Listen to the motor. If it bogs right when you whack the throttle open, then revs up, turn the air screw in 1/2 turn then try again. Do this until it revs up crisply. After the motor revs up, listen to it revving back down. If the revs drop quickly, and the motor starts to bog, and/or die, then you're too rich on the air screw, back it out 1/4 turn at a time. If after you let the throttle off the motor tends to run on and on while revving down very slowly, you're too lean and need to turn the air screw in 1/4 turn at a time. You want the revs to come up from idle quickly and smoothly, then drop back down to idle the same way. If you turn the air screw all the way in and it still needs to go further, then you will need a larger pilot jet. The opposite is also true: if you are backing the screw out so far that it darn near falls out, you will need a smaller pilot jet.

how do you do the plug chop

2012-04-20T07:52:00.000-07:00

Plug Chop

Basically a plug chop involves putting the bike under load at high revs

Chopping is where the igniton is cut at full RPM while the engine is under load

Hit the kill switch and pull clutch in fast , Slow down and with gloves on remove spark plug (hot).

the plug will have a colour which can be checked to given running conditions inside the cylinder.

Black = rich

Brown = good

Grey / white = dangerous conditions

air filters rs125

2012-04-20T07:41:00.001-07:00

Air Filters

If your thinking of getting an aftermarket air filter , They look good yes, get rid of the horrible box but theres a lot more to it thanjust putting it on.

If its genuinely a decent aftermarket air filter then it should let more air into your engine. Therefore you will need to alter the jetting otherwise your bike WILL seize.

Basically, to put your new air filter on, simply just remove the tank, remove the old air box and put on your aftermarket air filter. A lot say they will add quite a bit of BHP but you probably wont feel the difference, just it will give a better induction noise and maybe, maybe a slight boost.

Once youve fitted it you will need to do a plug chop.

or even better dyno test machine and having carb jetting set

AIR BOX MOD

First off the snorkel/trumpets...

Take the tank off your bike and you will see your air box, coming out of it at the top will be a piece of rubber called the snrokel/trumpet... People say take the whole thing out (people like me) other says pull it out, cut the end off that went into the air box then turn it around so that the end that was outside the air box is now inside it.

This will give a better induction noise, better midrange power, however people experience bad splutter around 5-6k, change your jetting and it should go and definatley do a plug chop.

Also, purchase another panel filter, e.g. CMP Racing, Pipercross. These are usually washable and oiled, this will give a better induction noise too and better running of your bike.

Again, id rejet not just stick it on.

suspension tweak rs125

2012-04-20T07:38:00.000-07:00

suspension

i would not personally alter a road bikes suspension set up they ride pretty much fantastic on normal settings , doing so is at your own risk .

Setting up your suspension.

sliding your forks up through the yokes 1.5cm will increase the angle of attack and turning speed of your bike.

You may need to adjust the rear shock after you have done this. Remember if your riding the roads dont tighten it right up, even if you think its good because thats what you do on the track, tracks dont have big bumps around corners. If you have it too tight your rear wheel will shudder out when you lean it over and hit an uneven surface. If its too loose the shock wont be able to react in time so when it hits two bumps it will probably still be on its way up when it hits the second bump.

sprockets rs125

2012-04-20T07:33:00.000-07:00

Sprockets:

This is how it works, the bigger your front sprocket the faster the top end, the smaller it is the faster the acceleration but the slower the top end.

The bigger on the back the quicker the acceleration the small the better the top end.

The standard set up is 16/39

That means 39 tooth sprocket on the back and a 16 on the front.

You can change the size of sprocketsfor more or less accelleration/top end.

A lot of people run a 16/40 and say acceleration is noticably better without sacrificing too much top end for the benefits of being quick off the line or even 15/40.

If your getting new chain and sprockets get the best. I know they cost a lot but it is well worth it. The last thing you want is a piece of string for the chain. It doesnt have to be O-ring but it helps.

If you get a half decent chain and look after it e.g. lube it, clean it then you should be alright. Just cheaper chains will need more adjustment and wont last as long. O-ring just helps keep all the lube in the chain really, makes them last longer!

2012-04-20T06:17:00.000-07:00

Carb

The older bikes uses a 34mm carb. The newer bikes have a 28mm carb. I think it was the 98's that had the 34mm carb on then after that unless modified it was a 28mm carb. If you want better mid range power, and a better top end fit the 34mm carb.

All you have to do is get hold of a Deloroto VHSB 34MM and a new inlet manifold because the original will be to small and then fit it onto your bike. The standard air filter will still fit this new carb.

Your bike is derestricted

exhaust derestriction

2012-04-20T06:14:00.000-07:00

Exhuast Derestriction

The later bikes 2003 onwards have a CAT in the expansion chamber. In the expansion chamber not the end can. To get rid of this CAT which makes your bike perform differently, get an after market expansion chamber (best buying the end can with it) or buy an earlier expasion chamber from an RS125 or take the expansion chamber off and be prepared to cut it open, remove the CAT and weld it back together.

If you are going to buy a different expasion chamber then you will have to rejet your carb. The bikes with a CAT in them are set to run rich (more oil) because the CAT requires the bike to run like this. Therefore you will need to buy a standard main jet for your carb. If you have a 28mm carb then your standard main jet size is a 120. If your carb is a 34mm your main jet is more likely to be a 158 You can get these quite cheap. This means taking your carb off and removing the old main jet, and replacing it with a new one.

The racers tend to use the standard expasion chamber because it is thicker then aftermarket ones therefore contains the heat more, and these work better with more heat. They normally just change the end can.

The expasion chamber doesnt really have anything in it anyway if your thinking this was too simple. Literally just cut it open, remove the CAT and weld it back together.

Some exhausts also have a recirculation tube that goes to the air box. You just have to cut this off and weld it up and seal up the air box.

The snorkel in the air box can be taken out too, this will let some more air in slightly and make your bike sound a lot better. Just pull the rubber out the top, or you can cut the part that sticks out. This shouldnt affect your jetting since the bike is not jetted correctly from standard anyways. If you want to be sure stick a bigger main jet in (121 on a 28mm carb). Do a plug chop to confirm.

Derestriction of the rs125

2012-04-20T06:10:00.001-07:00

CDI Derestriction
The Aprilia RS125 comes with a CDI restriction. It retards ignition around 6000rpm so the bike can pass EU emission tests .
This makes your bike perform very poor at 6000rpm
Derestricting this will invalidate your warranty.
If you bike is in warranty the best thing to do is buy another CDI and derestrict this and use it on your bike.

Derestricting the CDI,

The CDI will have a serial number on it? if the serial number is in the following format 071000-XXXX-XXXXX then this derestriction will work if done correctly (may still work on others).

You will need to cut out a hole in the CDI to reach the bridge. Cut out a rectangle 30mm by 10mm and 5-10mm deep.
You will see a part of a circuit board, snap this. This is known as the bridge. (If you reach glass it means you have dug too far!)
Once you have snapped the bridge, fill your hole back in with silicone, make sure its waterproof! Now there will be no environmental dip between 5000-6000rpm.
if this is too much for you , you can find ready derestricted cdi on ebay quite quickly.

Full Power Derestriction

The Aprilia RS125 can be restricted so its learner legal, and then derestricted to full power (claimed 33bhp). To do this you will need the following items:

o RAVE controller
o Powervalve blade
o Solenoid
o Cable

If your RS125 is restricted then it will not get a significant power increase around 8000rpm. If you know the powervalve is installed but you are still not getting this increase ensure all parts are working correctly, connected, and the solenoid is set correctly.

What does the powervalve do?
The blade of powervalve goes in the barrel of the engine. This then moves up and down to increase and decrease the exhaust outlet size to give you different performances at different rev ranges. The more revs you give the bike the more the powervalve blade is pulled by the solenoid and opens the exhaust outlet.
All a solenoid is, is an electromagnetic componet. Basically all you need to know is it pulls a cable which is connected to the powervalve blade to pull it out to increase the gap in the exhaust outlet.

You must check your bike for the componets listed above.
Your bike may be restricted via a blanking plate. You can see this by removing your right side fairing and looking above the exhaust. It will be a small plate and have 3 bolts along it (one either side and one in the middle). If you see a blanking plate then you will need to purchase the powervalve blade, mount, and other parts see parts diagram below... Your probably best getting a gasket for it too even though there is one on the blanking plate... you can reuse them but to ensure the bike performs well and you dont get any problems get a new one...

Once you have aquired these parts remove your blanking plate and fit the powervalve into the bike.
Note, the powervalve goes in one way!
It has a tapered end on one side, this should face downwards, and the flat side of the powervalve blade should face upwards! Ensure you do this!

If you can see the powervalve mount sticking out the exhaust then you will not need to purchase it of course and you will see something like this above the exhaust...

Remove your tank...
To the right of the battery there should be a solenoid which should have a cable connected on the end of it. The cable connects to the powervalve blade that goes into the engine that we looked at before.
It should look something like this altogether...

If you do not see the solenoid and/or cable then you will need to purchase these.
Once you have purchase these parts mount them to the right of the battery, there is a place for it to be fitted, it goes on the part of the radiator frame that goes right next to the battery.

If you see the solenoid and cable, and you see the powervalve mounted in the engine but your bike is not performing as it should... then it may be a case that the solenoid is not connected! If you look on the picture above there is a connector block on the end of the solenoid, see if this is connected, it connects to the main loom which runs along the right hand side of the bike from the front all the way to the back of the bike.
If you connect it up and it does nothing then keep reading....

Remove the passenger seat and check for the RAVE unit. (just remove the two back side fairings and tail)

If you cannot see this, then you will need to buy one of these and fit it to your bike. There will be a spare connector block coming out of the main loom were it should be connected to. Once you have fitted all these parts your bike should be derestricted!!!

All you need to do now is to set your solenoid up correctly... It has adjuster nuts on it, so the cable can be adjusted. This is because the solenoid starts acting around 3000rpm (you can see the solenoid opening when you rev the bike to this with the tank off). The more the powervalve blade sits in the exhuast the better low range power you will have, but poor top end. This works vise versa. See how to adjust your solenoid below...

WARNING: WHEN YOU DERESTRICT YOUR BIKE YOU WILL NEED TO CHANGE YOUR SPARK PLUG OTHERWISE YOU WILL BLOW A HOLE IN YOUR PISTON. Despite what the manual says, the spark plug to use when your bike is full power (powervalve installed) is a BR10EG. This is because the plug is colder. When your bike is restricted you should run a BR8EG. You can change these plugs for other versions e.g. Denso plugs, Iridium plugs for smoother running.

rs 125 common problems

2012-04-20T04:48:00.000-07:00

ive owned many rs125s bought sold and owned them .

this is not a comprehensive problems list but the most common problems ive come across.

fails to start after parking up for a few days/weeks

problem usually blocked jets , the jets inside the carb are very small and can clog up after log periods of parking up. this is why aprilia have fitted a fuel on and off tap , if you park it up for longer than a couple of day id advise to turn fuel off and let bike run out of fuel .
otherwise you may have to take carb off and clean out the carb and its jets out thoroughly.

electrical problems

low battery , faulty battery. these batterys are fairly poor and if left for long periods without riding cango flat and fail to recharge. try to run the bike regular or remove battery for trickle charging for period of long parking.

another problem can be faulty contacts in the wiring loom (block connectors) i always slit these put an electrical contact cleaner in them to ensure good contacts throughout the whole loom.
id do this yearly as rain , moisture can affect these joints .

if the bike fails the turn over but clicks , this is likely to be the relay situated near the radiator this is a device to turn the low current circuit of the starter switch into the higher current circuit of the starter motor .

basically this about it ive always found if you buy an old rs125 as long as the compression is good (ie piston rings good)
if you clean out the carb and jets ,replace old fuel with new fresh fuel , fully charge the battery or replace , make sure all electrical connectors are cleaned and fitted nicely then there should be no problem firing up .

BUYING A USED RS125

2012-04-20T04:11:00.001-07:00

Purchasing an RS125.

what are you looking for?

whilst buying an RS125 you have to be aware of the following:

They are not unreliable bikes, forget all the stories you heard. These are solid bikes. They are one of the most highly tuned road bikes, and as such demand high maintanence high quality oils and sensible riding procedures.

there is no bad rs125 just badly maintained ones

Yamaha R1 150 hp per litre , RS125 produces a massive 250 hp per litre!!!!!!!!!!!

this power demands race quality maintanence , avoid any bike that look uncared for unless your willing to

spend time on getting it back to tip top condition(which can be fun but expensive)

when first looking at a bike, check its mileage like any bike,check to see of its stolen recovered hpi clear or a previous insurance write off.

check the overall condition of bike in pacticular the braking systems , chain and cogs inside fuel tank (rust),does it start well from cold and sound good (listen to youtube videos for 125 bikes).

Be aware in the RS125 manual, it suggests you check your piston rings at 9,000km and change the piston and rings at 16,000km. So if its past these mileages ensure that this has been done by the previous owner.

an engine compression test is a good test to see if the engines piston and rings are good heres a video of how to do a compression test ensure you throttle is in wide open position

http://www.youtube.com/watch?v=rUXTZC_l2OU

if the bike has more mile saround 20/30000 for a well looked after rs125 then a complete engine rebuild should be done this will include barrel , piston, conrod , bearings etc etc .so bear this in mind when buying an older bike .

can you afford to rebuild complete engine , can you do this work yourself .

If you are purchasing a full power bike it will have a power valve in it. This is a mechanism that makes the exhaust outlet wider and narrower as the revs increase and decrease giving the best performance. The blade that moves in the barrel can sometimes get stuck. You should remove the power valve blade regularly and clean it to ensure it does not get stuck.The older bikes e.g. 1998 were the most powerful bikes manufactured As the years have gone by tighter and tighter emmsion controls have made bike less powerful.
If the bike doesnt get a significant power increase around 8000rpm then this bike is learn legal at 17 with a cbt. The bike can be fully derestricted to a claimed 33bhp by installing a power vale that I mentioned earlier.
The earlier bikes had a 34mm carb on them, but they were replaced with 28mm carbs. This means the newer bikes do not get as much mid range power. So if your test riding different years beware of this. You can always get hold of a 34mm carb and manifold inlet and put this straight on to the bike without any extra parts to get that performance.
Mods. If you get to an RS and its not standard make sure its been set up correctly. If you notice its got a fancy air filter on there make sure it has been jetted accordingly by the owner. If not the bike could be running lean! This is very bad, meaning a seizure is very likely when a bike is running lean. If you notice a different exhaust and expansion chamber, make sure it has been jetted. As if it originally had a standard expansion chamber with a CAT in it, it will be running far too rich. Not a bad things, just the bike wont run as well and the carb will have to be rejetted.

you will know a good RS when you see one. It will have been looked after properly. E.g. chain and sprockets are in decent condition, just the general condition of the bike. Self explanatory really.

APRILIA RS 125

2012-04-20T03:04:00.000-07:00

Chassis, suspension, brakes and wheels
Displacement:	124.80 ccm (7.62 cubic inches)
Engine type:	Single cylinder, two-stroke
Compression:	12.5:1
Bore x stroke:	54.0 x 54.5 mm (2.1 x 2.1 inches)
Fuel system:	Carburettor
Cooling system:	Liquid
Gearbox:	6-speed
Transmission type, final drive:	Chain
Frame type:	Cast aluminium sloping twin-spar
Front suspension:	Upside-down hydraulic action telescopic fork
Front suspension travel:	120 mm (4.7 inches)
Rear suspension:	Cast aluminium swing-arm
Rear suspension travel:	120 mm (4.7 inches)
Front tyre dimensions:	110/70-ZR17
Rear tyre dimensions:	150/60-ZR17
Front brakes:	Single disc
Front brakes diameter:	320 mm (12.6 inches)
Rear brakes:	Single disc
Rear brakes diameter:	220 mm (8.7 inches)
Physical measures and capacities
Seat height:	805 mm (31.7 inches) If adjustable, lowest setting.
Overall height:	1,135 mm (44.7 inches)
Overall length:	1,950 mm (76.8 inches)
Overall width:	720 mm (28.3 inches)
Wheelbase:	1,345 mm (53.0 inches)
Fuel capacity:	14.00 litres (3.70 gallons)
Reserve fuel capacity:	3.50 litres (0.92 gallons)