Preparing the metal cover has been quite a bit of work, I had already prepared the top side of the cover by removing the paint, rust and dents using elbow grease, however I decided that I should also remove the rust from the underside of the cover too before I respray – If a job’s worth doing, it’s worth doing well!
Recently I have been looking into ways to restore old rusted tools and I have been very intrigued in the method of using electrolysis to remove rust. During the past week I had been doing a bit of research online on the subject and I tested it on an old rusted ring spanner which cleaned up quite well. I decided it was a good way to remove rust off parts of the mower without much effort (don’t work harder, work smarter) and the result above speaks for itself! I wont go into the specifics of the rust removal in this post, I’ll dedicate another post to it shortly as I didn’t take enough pictures of my set-up, however in the meantime if you are interested this site has great information on rust removal by electrolysis, there are also many tutorials on youtube.
My compression test kit arrived, so I bolted the head back on to do some testing. The kit came with quite a few adapters to suit different engines / spark plug holes so it should be a handy kit to have around. To perform the test, I simply pulled out the spark plug and connected the compression tester in its place. I pulled the pull-start cord a few times and checked what pressure was reading. I never seemed to get a reading higher than 50psi which I thought was extremely low and not only that, but the pressure would drop away very fast! I need to confirm if it is the engine or the test kit itself, the Nitto style air fittings that the test kit uses seem too loose to me so I will hook it up to an air compressor with a regulator to verify none of the fittings are leaking.
Even though my compression test seemed unsuccessful I decided to go ahead and continue with pulling apart the engine, I took the head off again, then removed the valve spring cover and proceeded to remove the valve springs. The valve spring retainers are buggers to get off, the intake valve spring came out easier than the exhaust valve spring, but once I got both of the springs out I noticed that I could not pull the exhaust valve out of the case whereas I could pull out the intake valve fine. On closer inspection it appears that the base of the valve where the valve spring retainer pushes against has been put under a lot of force and expanded the diameter of the valve stem and now it wont fit back through the hole. I am not sure exactly how this could happen unless the valve was somehow obstructed and could not be push all the way open, but if that had happened then I would have expected the valve to be bent. I noticed when the valve is fully closed it is not seating very well due to all the crud build up underneath it, this could be a reason for the low compression (I hope). I have a new exhaust valve on its way so I think I will replace it. To get the exhaust valve out I had to use a sanding wheel on my Dremel to grind the diameter of the base of the stem back to size.
Next I need to remove the top and bottom flywheels (bottom flywheel has the blades attached), unfortunately I never seem to have the right tools around. I really could use an air impact wrench / rattle gun to remove them… Till next time…
I have a bit of an update to my Briggs rebuild, I pulled off the head and inspected the carbon build-up on the piston and valves, as you can see from the image above its quite a lot! and a large piece actually fell out as I was taking the head off. I have since cleaned this up with a wire brush and it’s looking much better now. I will be putting the head back on shortly to test the compression before I replace the piston rings and lap the valves.
Below is an image of most of the peripheral parts laid out on a shelf ready for cleaning (more thoroughly). After pulling the carby off the fuel tank, it looks like ill be needing a new diaphragm.
I have also striped back the paint off the steel cover using some thinner and sanded back most of the rust with 100grit sandpaper, some of the deeper stuff I had to use a sanding wheel on my Dremel, there were quite a few dents in the front and I have managed to ‘panel beat’ most of them out and clean the rust out of the pits, a few smaller dents remain which I will fill before respraying. Hopefully I will get a chance to respray it tomorrow before it starts to form rust. I purchased some red engine enamel and my new Briggs & Stratton decal sticker has arrived, so it should come up a treat!