More HORRIBLE News

[Coyote]

Just for giggles I decided to run a compression check on the 550 project of mine. I came away NOT giggling. Right 120. Center 125. Left 23. I give up.

[yeadon_m]

Urhhg! Hole in piston, smashed rings/lands or....big leak from head gasket?

[Coyote]

No visible hole in piston -- looking through the plug hole. The spark plug that came out of that cylinder looks like it was burning perfectly. Retested with the same results. Around 20.

[Cliff]

Pull the exhaust pipe off and have a look in the port. Roll the engine over, check the piston, rings, bore etc...

[Coyote]

Pull the exhaust pipe off

The only thing I'm ready to pull is the rest of my hair out. The idea was to get this thing running BEFORE tearing it down to do the cosmetics. Obviously That's not Murphy's plan. Can't even look at it now. Will probably remove the head tomorrow and have a look. One thing for sure is it ain't a bent valve. There is so little to these motors I can't begin to imagine what's wrong.

[Coyote]

Max pressure left cylinder. And no, the head gasket is not leaking.

[diamondj]

That is the one advantage on a 4 cycle engine - at least then you could have a stuck valve.

If you're lucky someone put it together without the piston rings on that cylinder.

Head gasket leak from a warped head would have been my first guess. Maybe try a pressure test and see if you can hear it leaking?

Good luck!

Jim

[tz375]

Chris, Remove the left engine covers and the alternator and place a drip tray under the motor. Then pour kerosene into the left cylinder and pounds to peanuts it pours out of the left main bearing. That seal gets dry and tears itself apart.

[Alan H]

Chris, Remove the left engine covers and the alternator and place a drip tray under the motor. Then pour kerosene into the left cylinder and pounds to peanuts it pours out of the left main bearing. That seal gets dry and tears itself apart.

That wouldn't affect the compression above the piston though.

[yeadon_m]

Not sure - if the seals are gone, it won't suck, surely, so its got far less air to compress?
Reveals my limited understanding of how a two stroke works
Mike

[Cliff]

Actually it's the other way around. If the seals are gone it won't compress the incoming air charge in the crankcase. One thing that hasn't been mentioned is a plugged exhaust pipe/muffler. Pull the pipe off and check your compression. Remember to have the throttle wide open when testing too.

[Coyote]

Remember to have the throttle wide open when testing too.

eer, there ain't no carbs on it.

[locobuilderbri]

Chris, Remove the left engine covers and the alternator and place a drip tray under the motor. Then pour kerosene into the left cylinder and pounds to peanuts it pours out of the left main bearing. That seal gets dry and tears itself apart.

That wouldn't affect the compression above the piston though.

Piston ported two stroke engines rely on crankcase compresion to deliver the fuel air mixture back into the cylinder above the piston for further compresion before its ignited, So its very likely a crankshaft seal has gone!
Not what you want to hear I know
Hope it all comes good in the end.

[tz375]

Or take off the left pipe and plug it and the inlet with rubber plumbers stops and blow air in through the plug hole and see if it compresses or if it hisses out.

Check the left pipe for blockage is a good idea too.

[Coyote]

Head is off Bore is scored pretty bad and the edge of the piston has broken off nearly down to the top ring. Next is to pull off the exhaust and SRIS lines so I can remove at least that jug. I need to go out now. Will post more later with pics.. The piston top breakage is adjacent to the exhaust port. Later.................