Successful bandaid fixes for compression loss on small engines

[BigMike50]

I have a 20 year old 4 cycle 1 cylinder Yamaha golf cart. Compression should be 150-175psi. My compression reads 100 psi at full throttle. Putting engine oil in the spark plug hole raises compression to 150. Thinking bad cylinder wall or piston rings. Is it possible that carbon buildup on the rings is creating a bad seal? Was thinking off shooting water through the intake on a hot engine to steam clean it. Then possibly using engine cleaner additive to oil. Lastly, through a full bottle of Lucas compression restore in the crank case. Any thoughts or experience? Yes I know how to rebuild engines but won't have time to do it till winter. The cart runs good but not as it used to. Kinda sluggish.

 

[sox3]

If the rings are carboned and stuck I don't think the steam method will work. You need to do a leak test to see where the pressure is going.You could have a leaking valve, intake or exhaust. Exhaust is common on a lot of engines. could have carbon on the valve or seat.

 

[BigMike50]

Thanks. I'll have to pick up a leak down kit

 

[sox3]

If you have an air compressor, lock the shaft with the motor at top dead center, pull plug and
put some air in the cylinder. If its leaking out the valves, you will hear it in the carb or muffler.
if its passing into cylinder, it will be coming out breather or dip stick. The leak down testers
are a great tool.

 

[BigMike50]

Yeah I have an air compressor. I just don't have anything to adapt to the spark plug hole. I found some relatively cheap adapters for under 15 bucks on eBay. That should work huh

 

[Soundguy]

just do a dry comp test, then wet. and compair.

so far you have said you have a significant increase on wet. that points to rings.. not valves.

you think it's carboned?

pull plug and dump a can of seafoam into the jug and let it drian thru.

change oil

and then run..

my call onthe bandaid fix?

put a set of rings in it. crosshatch the cyl.. ream the ridge. put bearing shells in it if you can get them.. and hand lap the valves.

that's a cheapy poor mans rebuild.

 

[Don87]

Soundguy is spot on as usual.

For carboned vavles, I've a pretty good luck at dribbling water through the carb while the engine is running at least at half throttle, it will knock the carbon right off the valves.

But if you are going to keep the machine, and think it's worth it............fix it right. In another 20 years it probably won't need fixing again.

 

[94BULLITT]

It sounds like the engine is getting tired. On the cheap you could tear it down, hone it, and put a set of rings in it. I would not waste time putting any additives in it, they may do more harm than good.

A popular swap for golfcarts is a old snow mobile engine. I figured I would throw that out there

 

[BigMike50]

It sounds like the engine is getting tired. On the cheap you could tear it down, hone it, and put a set of rings in it. I would not waste time putting any additives in it, they may do more harm than good.

A popular swap for golfcarts is a old snow mobile engine. I figured I would throw that out there

been looking into the snowmobile swaps. Also considering one of the direct swap big blok conversions from buggiesunlimited. its like 2k for everything turn key. even comes with clutch and exhaust. Not bad imo. the snowmobile swap would be shiit loads of power. probably more than I could use but well worth it. more fabrication would be need though

 

[BigMike50]

well I did a leak down test but not with a gauge. I just hooked up air to the spark plug hole while at top dead center on the compression stroke with both valves closed. Air was blasting out of the carburetor. So what I did was forced the intake valve open and closed aggressively with a heavy screwdriver and shot some cleaner through the valve. I didn't have much faith in it but Whata you know! I did another air test and it sealed up! I did another compression test and got 155 psi. I don't know whats up but something got lodged in the intake valve. She is running good now