Shane
Have you posted about this engine previously, sounds familiar to me…
Did you replace the piston rings? I seem to remember a post about an engine that couldn’t be made to run after replacing the piston rings, so forgive me if I am confusing your current post with an unrelated one…
First, if you did replace the rings, did you get the piston oriented correctly back in the cylinder? The sharp side in the piston dome reflector needs to face the intake parts, which are on the right side of the engine block when viewed with the cylinder head facing you.
These engines run pretty well, until they don’t…..In other words, when they are worn out internally, they tend to be hard starting, idle poorly, and don’t develop full power. Your compression sounds OK, but new rings are only half the story here. Piston skirt fit to the cylinder wall is critical to ensure the correct intake charges are developed and delivered to the combustion chamber. In other words, you could have great compression, but poor crankcase sealing. And yes, the lower seal on these engines is a common issue. When water gets into the lower needle bearing, things go south quickly, this affects the lower seal also creating a crankcase leak. Damage is usually pretty obvious when you remove the lower seal/bearing/housing…But, be careful, sometimes the needles love to fall out of a serviceable lower needle bearing when it is removed. You may have honed the cylinder oversize when you had it apart, did you hone the cylinder? In any event, if you decide to disassemble the powerhead again, it is crucial to measure the cylinder bore and piston skirt carefully.
All that being said, it is important not just to “assume” this engine is worn out internally. You mention that the engine “hunts/lopes in RPM” at high speed as well as low speed, which is an interesting symptom. I have never encountered a worn out 2hp that hunts, usually just is hard starting/poor idle/low on WOT power. Hunting surely sounds like a fuel delivery problem. I know you said the carburetor looked pretty clean inside, maybe there is a problem with the fuel valve on the tank, these get pretty rusted/crapped up, I’m sure you have already replaced the fuel line. These carburetors usually don’t wear out, but can be damaged from lack of use, corrosion/rust. Oftentimes the throttle shafts get stiff and don’t move easily. Forcing a seized throttle shaft can cause further damage by bending the shaft or distorting the butterfly valve. The easiest thing to do would be to just try another carburetor, but I’m sure you don’t have one on hand…I might have one, will look when I get home. I suppose the reeds could be damaged, it is not difficult to pull the intake manifold and have look also. Like others have said, packing nuts that are loose can create an air leak also. An ignition issue is possible, though unlikely. Like I say, these engines usually suffer from lack of use, things getting rusted and jammed. So, a stiff set of ignition points might created a running issue like this, the point cams often get rusted on these engines also, make sure the oiler wick is in place and properly lubricated.
I know you see this as a fun project, and it is for sure. But, it is easy to spend a lot of money on powerhead repairs, so I don’t recommend getting in too deep on this little engine.