Briggs & Stratton Compression Test

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…

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