Briggs & Stratton 8hp Engine Internals Complete

This article details a method I used to fix a large hole in the crankcase of a 8hp Briggs & Stratton Vertical Engine.

First a little background:

When we first bought our property we quickly realised we would need either a tractor or a ride on lawn mower. Whilst I would have loved a tractor, cost meant we went for a ride on lawn mower. However this ride on mower was unique. It was a 1977 Rover Ranger mower. Go Kart style steering, Briggs and Stratton engine, all steel construction, etc.  Built solid as a rock but it was in need of some work. After about 6 months restoring the mower it was ready for testing – restoring the mower not the engine that is.

With the mower restored I added some oil, fuel/gas and gave the engine pull cord a tug, then another tug, and another…eventually I got the engine going. The mower worked great! Cut through thick grass, drove hard, ran smooth -though fast until… I hit a brick. Hidden in the long grass was a house brick and after hitting it at full speed something had to give. Normally this would be the mower blades. However, unknowingly at the time, the previous owner thought it was a good idea to weld the blades fixed. The engine did not like this and after spluttering a little decided the connecting rod (conrod) was the piece of metal that had to break. Sadly as it broke it put approximately a 5cm/1.5″ hole in the crank case wall. Not surprizingly the mower then stopped.

I was devastated. Months of work were now down the drain. A hole in the crankcase surely was unrepairable – especially since I’d never opened up an engine before. Consequently the mower was wheeled into the shed and left for a week. That week was a slow week. However, it also gave me time to think about the motor with a clear head. In particular: Why is a hole in a crank case unrepairable? After eventually pulling the engine apart I came to the conclusion I would try and repair the hole.

The hole was in the side wall, the conrod had created a few additional cracks as it flew through the crankcase side wall, but in general the engine looked repairable. Luckily when the conrod went, the various small pieces of broken conrod didn’t destroy any of the valve stems, oil slinger, etc. The main damage was the side wall.

Initially I thought “I’ll just weld something over it”. That was a nice theory but I very quickly discovered that the crank case was made from cast aluminium. One touch with the Arc welder and it would turn to molten metal! (Aluminum melting point is quite low in comparison with steel – about 700 degrees C vs 2300 degrees C). Hence my options were either TIG weld the case or find some other method of repairing it.

Sadly I’m not rich enough to own a TIG welder and none of my friends had one either. Hence I was left with finding some other method of welding aluminium. After searching Google I found out about a product called Durafix. Durafix is a type of welding rod, or more accurately a solder rod that can be used on aluminium. A little more searching revealled there was a number of products on the market that do a similar products. These can be found by searching for the names Alumaloy, Aladdin, HTS2000. They all do the same thing. So I started looking around for some of these welding rods. Sadly they were not cheap. Hence before I bought them I thought I’d check both prices of new engines as well if the rest of the engine I had was still any good.

New engines turned out to be much more expensive than I thought and I sadly I soon found the piston didn’t run smooth.

Piston with scoring marks from sanding to fit cylinder

One of the side effects of the conrod giving way is the rod arm in the piston had slightly deformed the piston. Hence it wasn’t correctly round any more. At this point I realised I needed a parts list. Going to Briggs and Stratton’s website I punched in the engine numbers and guess what – the parts list was still available. So after ringing around locally and checking Ebay I discovered a new piston wasn’t cheap. Especially since I didn’t know if I could repair the engine. I left the entire project for a few more weeks whilst I thought about what to do.

I eventually decided that if I could get the piston running smoothly I’d get the welding rods and try and repair the crank case. After all a set of aluminium welding rods could always come in handy. The problem was how to fix the piston. Everything I read said it had to be machined round, or replaced. I thought to myself, this is just a lawn mower, not a Ferrari V12. So I did the next best thing. I put the piston in the vice and crimped it until it was reasonably round. This got most of the shape back but it did still catch a little. (A note for anyone attempting a repair, I found the piston would only correctly work when put in from the bottom of the cylinder, it wouldn’t fit from the top).

To fix the small catch that it had left I sanded the side wall of the piston. I figured since it’s only the side wall the worst that would happen is a little movement (later I found out this is called piston slap and can be harmless or can destroy the rings depending on the amount of movement).

With the piston now running smooth I bought aluminium soldering rods off Ebay (It was cheaper to buy them in the US and get them shipped to Australia than buy them in Australia). After a few weeks they arrived and I replicated a couple of youtube videos I’d seen that welded coke can together. This was pretty easy stuff to work with – so I thought. Turns out small things are easy! The biggest issue was I was working with a large crank case.

After cleaning up the crankcase as best as I could with degreaser, some elbow grease, water and a stainless steel brush (as it

doesn’t cause the aluminium to oxidise) I began to heat the case. I’d borrowed a propane blow torch for the job and also had my electric heat gun. Initially I used the heat gun to get the entire crank case to a temperature where it was hot to touch (Electricity wasn’t a consumable like the propane tank).  I then used the propane torch in the cracked areas on the welding rods. It took ages!! Heating, heating, and more heating. Eventually the crank case got hot enough.

(At this point a little side note. The best way to use the welding rods is to heat the surface you want to repair. The rods are designed to melt below the melting point of aluminium. If you heat the rods they just turn in to little solder blobs but never cling to the surface your trying to weld. If you heat the surface your trying to weld then touch the rod to it, the solder melts and clings to the surface).

Finished Weld

With the surface now hot enough (hot enough to smoke the plastic grips in my vice), I began welding…er soldering. It was at this point I realised fixing this would be a little tricker than expected. You see the rods are more of a solder than a welding compound. My aim was to weld a piece of scrap aluminum I’d picked up at a local steel recycler over the hole on the outside of the crank case, then seal the inside with more weld. Being a solder this was a difficult task. The outside weld went perfect. The inside on the otherhand was not so successful. Turns out because the rods are a solder, touching the inside of the piece of aluminium covering the hole, ended up shifting the outside (as the piece was sitting on a layer of molton solder). Quite a few attempts later I had finished the repair.

Sealing the inside of the crankcase with liquid gasket

After 2 hours cool down time (the case took that long). I then did a water test for leaks. Drip………….Drip…….. Drip……… sadly the weld was not water tight. Due to time constraints and limited propane, sadly I could not reweld the case. Instead I applied liquid gasket to the inside of the weld, let it set the retried the water test – I was now water tight – success!

So with the case welded, it was a matter of putting the engine back together. (See the shots below for step by step instructions). By this time I had already bought a new after market conrod which fitted perfectly and despite quite a few mistakes where I had to take bits apart to put other bits in I eventually got the engine back together.

With the engine together, I added oil, petrol a new spark plug and crossed my fingers. I tugged on the pull cord….then again… and again… finally, the engine coughed to life. After quite a bit of spluttering whilst I adjusted the carby, it was running really nice. Time to put some load on it  – This time I had removed the fatal welds on the mower blades, if I hit anything THEY were going to give first.

The mower worked a treat, ran smoothly – after a few adjustments (the safety wire on the flywheel was rubbing against the flywheel cover making a awful noise) and kept running well.. so I thought.

It wasn’t until about 15 minutes into mowing I noticed the excess smoke coming from the mower. There was a little smoke as it accellerated but the amount of smoke had certainly increased quite noticable. Not wanting to destroy the Briggy any more I stopped the mower to inspect what was happening. Sure enough there was a small leak of oil through the weld.

You see Briggs & Stratton engines are designed to run with a negative pressure in the crank case. This helps suck the oil back down when the piston drop and prevents excessive oil burning. Without this negative pressure the oil get up to the combustion chamber and burns – also makes a nice black coated spark plug.

That’s what was happening here. The leak in the crank case weld was letting air in, stopping the back pressure and causing oil to burn. As a quick fix I wedged some metal putty over the hole, topped up the oil and tried again.

It still smoked and leaked. Though dramatically less than the first time. A little more putty and practically no leaks.

So now 5 months down track with the mower use pretty much ever weekend (A lot of grass grew whilst I was repairing it). The repaired B&S 8hp is still going strong. By using some premium unleaded (98 octane) it’s got a lot more punch, and getting the right spark plug gap (0.3″/.72mm)  it works very well.

When summer comes and I can’t mow due to the temperature (due to bush fire regulations). I intend to rip the engine apart again and reweld-solder the cover plate I put over the hole, and not give up until it’s water tight.

I’ve also learnt a lot in the process of doing this. All about engines, how to get them running, keep them running etc. A tip I want to try with the welding is to use a dremel and carve a V groove before welding. Especially over the cracks that are hairline but widen as the engine heats up this should fill them better. (This tip was from a site asking about welding a motorbike crank case with JBWeld – though I can’t find the link again). I also think I’ll purchase a rebuild kit and replace the rings to help eliminate smoke due to a worn piston/rings. The engine runs well enough to justify this. The rebuild kit also has a complete gasket set which will help.

So if suddenly you find yourself with hole in your crank case, a broken conrod and a warped piston,  but otherwise the engine looks fine, don’t believe everyone that the engine is scrap metal. You just might be able to fix it yourself!

Putting a 8hp Briggs and Stratton Engine Back Together

If you have friends or family who are often offering to lend you a hand with various tasks, then it can be a great idea to take them up on the offer when you are moving house. Be clear about what needs doing, and give anyone who volunteers specific tasks to carry out, in order to make the most of the help which you have. Often, it is the most menial tasks which can prove to be the most time-consuming when moving house, so it can be extremely useful if you have a group of willing helpers. Just make sure you’re willing to return the favour in the future!

Make a list of what you are likely to move shortly after your move, and make sure they are easily accessible. It is a good idea for each house member to pack a small holdall for a few days, so that they will not require immediate access to the rest of their belongings. In addition to clothes and toiletries, you may also want to make sure you are able to set up your computer shortly after your move – not just so that you can relax with a game of partypoker, but to help you get in contact with anyone you might need to speak to regarding any problems which you may have encountered while moving. You may also want to get appliances such as your fridge up and running as soon as possible, so that you will be able to store basic food provisions.

Lastly, remember to label EVERYTHING. Keep track of your belongings as best as possible, so that you can easily check if anything has gone missing. Don’t let important documents get lost in the move, and protect anything which is breakable. If you follow these basic guidelines, you can help to make move day as straightforward as possible.

Whilst working on an application that makes use of a 1394a/firewire camera I found a strange bug/feature with libdc1394. The problem was dc1394 was being used to the mode of the camera to 800×600 resolution. However, when querying the frame size after dequeuing the frame, the size was only 640×480. Ie: See the below snippits:

..
dc1394error_t result = dc1394_video_set_mode( this->camera, DC1394_VIDEO_MODE_800x600_RGB8);
if( result != DC1394_SUCCESS )
exit(0);
 
....
dc1394video_frame_t *frame=NULL;
dc1394error_t result;
 
// capture one frame
result = dc1394_capture_dequeue( this->camera, DC1394_CAPTURE_POLICY_WAIT, &frame );
if( result != DC1394_SUCCESS )
exit(0);
 
// Allocate image memory if required
if( this->lastFrame.image == NULL ){
memcpy(this->lastFrame,frame, sizeof(dc1394video_frame_t));
this->lastFrame.image = (uint8_t *)malloc(frame->total_bytes * sizeof(uint8_t));
 
..

At this point total_bytes was 921600 which works out to be 640x480x3 (RGB);

I was stumped. I asked for one mode and got another back. All with no errors what so ever from libdc1394.

After over an hour of debugging, google searching and more,  I eventually found the reason.  The comment that ended up in the code explains the cause:

// Shutdown any isotransports that are setup for the camera.
// It turns out that libDC1394 will quite happily let you set modes,
// framerates, etc but if there is an iso stream running none of them
// will actually take affect. Hence you can set a 800x600 res and get
// back 640x480 video frame - really nice libdc1394. It could at least
// indicate there was a active stream when setting the mode!
// Anyway to deal with this we force the camera to stop capturing
// before we change the settings, if the camera was capturing prior to
// setConfiguration being called, we restart the capture

So the solution is to make sure the iso transmission stream has been shutdown. this can be achieved using:

dc1394_video_set_transmission( this->camera, DC1394_OFF );
dc1394_capture_stop( this->camera );

An easy fix but certainly an annoying setup. I’ve not tested it but I’m guessing many of the other functions:

• dc1394_video_set_framerate
• dc1394_video_set_iso_speed
• dc1394_feature_set_mode
• dc1394_video_set_one_shot

are also affected.

Recently I was working on a piece of code that updated a texture with a camera frame. The application was using the fixed function (non shaders) pipeline of OpenGL. Whilst I didn’t notice it at first, I soon found that the camera image was very delayed. For example the camera was capturing at 30 frames per second, but the screen update rate was only 6 frames per second.

After commenting out vast amounts of code, disabling functions the reason behind the slow frame rates was traced to the OpenGL call: glTexSubImage2D. The exact call that was being made was:

glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0,  mWidth, mHeight,  GL_RGB, GL_UNSIGNED_BYTE, image->getData());

Everything to this call looked normal. I tried a simple test program that used glTextSubImage2D and surprizingly it ran fast! So at this point I was a little confused. How could two very similar programs produce different results.
I kept searching. I tried Google searches found various comments but none of them seemed to work.

Eventually I looked at the Texture class I had been using and began commenting lines out of that. It was only when I found and commented out the line:

glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE );

Things improved. This makes perfect sense as well. Generating a mipmap each frame is expensive. A quick fix and the application was running smoothly!

Rich Short Crust Pastry

A little while ago I was making a quiche and found I had no shortcrust pastry left. Rather than ducking out to the local shop and buying some I decided to make some. Searching through the recipie books I had I found a the following recipie (per Breville Inspirations book)

Recipie:

• 180g butter chopped
• 2 & 1/4 cups plain flour
• 1 & 1/2 teaspoons baking powder
• 1/4 teaspoon salt
• 2 tablespoons lemon juice
• 1 egg yolk, lightly beaten
• Extra Flour for kneading

Steps to make the pastry

1. Using a beater, cream butter until soft.
2. Add flour, baking power and salt. Gradually add lemon juice and egg youlk to form a slightly crumbled dough.
3. Tourn dough onto a lightly flour dusted board and knead lightly to form a smooth ball.
4. Wrap dough in plastic wrap and refrigerate for 20 minutes before using

Things to remember

After making this recipie there would be a few things I’d change for next time. The pastry is Very rich and hence I’d add the entire egg rather than just the yolk. Also the comment about refrigerating for 20mins depends on how cold the pastry is before it goes in the refrigerator. Don’t do what I did and refrigerate it all day until you make the quiche that night – the pastry will be rock hard and need microwaving before you can even make an indent in it!

Also remember to blind bake this pastry. (That is bake it for about 20minutes on 200 degrees Celcius) before filling it. If you don’t do this it might not be cooked before your filling is!

[Thu Jan 20 14:15:16 2011] [error] Oops, no RSA or DSA server certificate found for 'www.somedomain.com:0'?!

Whilst somedomain.com isn’t the official domain name reported (I can’t reveal the client), this error was being printed for every SSL host except the default SSL host. Ironically the default SSL host was simply a redirect to one of the others. A quick check and indeed the problem lied with the SSL hosts – we removed every ssl host and the webserver would start fine – obviously without any ssl.

My colleague and I were  perplexed. He’d tried a quite few things to fix this all without luck. A so call Server Admin told him it was due to not using ip based virtual hosts for ssl, he claimed you can’t use Name Base Virtual hosts with SSL. No doubt this was obtained from a quick google search for the error. The problems is you can run NamedBasedVirtual hosts with SSL on port 443 provided you have a wildcard SSL certificate. A wild is required for NamedBaseVirtual hosts as the SSL connection is established first before the headers are sent. A wildcard will allow any subdomain to use the SSL connection then apache will see the host header and respond with the appropriate vhost. If on only have a single certificate this does not work and you’ll need a separate IP per certificate.

Anyway, we began trying to debug the issue. First we checked the certificate files were at the specified locations – they were. Next we checked the certificates were actually valid. You can use the openssl command below to do this:

openssl x509 -noout -text -in YOURCERTIFICATE.crt

The certificate, key, and certificate authority (CA) were all valid and in date.
Next we tried putting each Vhost in to the config one by one to see if one host had errors over another. Turns out it didn’t matter what order each host was in the config file or which ssl hosts were included, they all had issues – except for the default ssl vhost.

At this point we were a little lost. So we decided to go back to basics and work out what the error really meant. We search to see what apache module the error came from. A simple grep later we’d narrowed down the error to mod_ssl. A search of the mod_ssl source code found the following instance of the message:

# grep Oops *
ssl_engine_init.c:                         "Init: Oops, you want to request client "
ssl_engine_init.c:                "Oops, no RSA or DSA server certificate found "
ssl_engine_init.c:                "Oops, no RSA or DSA server private key found?!");
ssl_engine_io.c:                    (argp != NULL ? "(BIO dump follows)" : "(Oops, no memory buffer?)"));

Looking in ssl_engine_init.c we found the error came from the following function

static void ssl_init_server_certs(server_rec *s,
                                  apr_pool_t *p,
                                  apr_pool_t *ptemp,
                                  modssl_ctx_t *mctx)
{
    const char *rsa_id, *dsa_id;
    const char *vhost_id = mctx->sc->vhost_id;
    int i;
    int have_rsa, have_dsa;
 
    rsa_id = ssl_asn1_table_keyfmt(ptemp, vhost_id, SSL_AIDX_RSA);
    dsa_id = ssl_asn1_table_keyfmt(ptemp, vhost_id, SSL_AIDX_DSA);
 
    <em>have_rsa</em> = ssl_server_import_cert(s, mctx, rsa_id, SSL_AIDX_RSA);
    <em>have_dsa</em> = ssl_server_import_cert(s, mctx, dsa_id, SSL_AIDX_DSA);
 
    if (!(have_rsa || have_dsa)) {
        ap_log_error(APLOG_MARK, APLOG_ERR, 0, s,
                <strong>"Oops, no RSA or DSA server certificate found "
                "for</strong> '%s:%d'?!", s-&gt;server_hostname, s-&gt;port);
        ssl_die();
    }
 
    for (i = 0; i &lt; SSL_AIDX_MAX; i++) {         ssl_check_public_cert(s, ptemp, mctx-&gt;pks-&gt;certs[i], i);
    }
 
    have_rsa = ssl_server_import_key(s, mctx, rsa_id, SSL_AIDX_RSA);
    have_dsa = ssl_server_import_key(s, mctx, dsa_id, SSL_AIDX_DSA);
 
    if (!(have_rsa || have_dsa)) {
        ap_log_error(APLOG_MARK, APLOG_ERR, 0, s,
                "Oops, no RSA or DSA server private key found?!");
        ssl_die();
    }
}

Hence  the error was caused by the certificates not being able to be imported. Once again we checked paths to make sure the certificates/keys were correct. Alas they were. So we began to wonder why the certificates couldn’t be found. We’d specified the correct files, confirmed they were correct. It occurred to me that perhaps the openSSL context had not been setup correctly. But why not? I took a look at the default SSL vhost which did work and noticed a single line that were not in any of the other ssl vhosts.

SSLEngine on

The comment above this line read:

#   SSL Engine Switch:
#   Enable/Disable SSL for this virtual host.

I added “SSLEngine On” to the other ssl vhosts and it worked! So it turns out you can have an vhost setup on port 443 without SSL hence for each vhost you want SSL working in you must add the above line. My colleague was extremely thankful – why it happened in the  first place, we still don’t know. We suspect previously the option may have been enabled globally. However the fix allows apache to run again and works after a clean shutdown and startup.