In an earlier post I mentioned getting 2 old minibikes for 100 dollars. Both have 3.5 hp Briggs engines; but "The Cat Dominator" would not start and had no compression at all. I was about to remove the engine, and install an old Montgomery Wards engine I have, made by Briggs & Stratton, but used on a Wards garden tiller.
Anyway, I pulled the head to see what was wrong. The engine was clean and perfect inside, no ridge at the top of the cylinder, no burned valves or hard carbon. In fact, the engine looked almost new inside. But, the intake valve was stuck open. Looking under the valve I saw something glinting in the light. It was a small machine screw, barely 5/8 of an inch long; and it was sticking the valve open.
I tried raising the valve with a screw driver beyond its normal lift, but I couldn't get the screw out because the screw head was still too wide to clear. So, I removed the air cleaner, and then loosened the two screws holding the intake manifold to the cylinder; then lifted the bike up in the front so that the screw could drop out. I believe that the screw had been in there since the engine left the factory. The screw couldn't have entered through the spark plug hole, and it was unlikely that the screw had entered through the carburetor.
After putting things back together, the engine started first pull, and settled down to a nice idle. I could have ridden the bike, but the chain is missing. In the sixty years I've messed with Briggs & Stratton engines, I've never seen anything like this before. :no:
Anyway, I pulled the head to see what was wrong. The engine was clean and perfect inside, no ridge at the top of the cylinder, no burned valves or hard carbon. In fact, the engine looked almost new inside. But, the intake valve was stuck open. Looking under the valve I saw something glinting in the light. It was a small machine screw, barely 5/8 of an inch long; and it was sticking the valve open.
I tried raising the valve with a screw driver beyond its normal lift, but I couldn't get the screw out because the screw head was still too wide to clear. So, I removed the air cleaner, and then loosened the two screws holding the intake manifold to the cylinder; then lifted the bike up in the front so that the screw could drop out. I believe that the screw had been in there since the engine left the factory. The screw couldn't have entered through the spark plug hole, and it was unlikely that the screw had entered through the carburetor.
After putting things back together, the engine started first pull, and settled down to a nice idle. I could have ridden the bike, but the chain is missing. In the sixty years I've messed with Briggs & Stratton engines, I've never seen anything like this before. :no: