compression release???

[oneb1jap]

have a bashan sunl cg6 water cooled 250cc quad: been a while since worked on it so symptoms is : try to spin it over - it won't. might get one compression stroke - but not two. went with new starter, battery, wiring, valve adjustment, socket on flywheel - it will revolve
got to my wits' end long ago
haven't pulled the head because can't see a gasket on VMC,
under rocker cover is a hole off to side near intake.
I'm thinking stuck compression release.
Hope any of you can be helpful,
what to do
where to get parts, etc,
thanks

[JerryHawk250]

You will only get compression on every other stroke. The second stroke is to release exhaust.

[oneb1jap]

I've thought about this problem and guess will tear down more.
Don't know how to upload a picture but have figured out ( surmised ) :
camshaft cover is on left side; must be short length due to being at bottom of jug;
a ridge rises about 3 inches to a hex nut; that should be the compression release with somehow a rod connection to cam; push rods would be on this side of the jug & how then could a fly weight valve lifter fit to temporarily hold up a valve?
With now book before pullong the jug I am at almost a dead end.
If no advice from anyone - - after a while will remove that top bolt & see if maybe solvent down the hole will free up something.
Comments please. thanks

[krat]

It appears that you are assuming your engine is much more technically advanced than it is. I have been inside the CG many times and have found nothing I would consider a compression relief system.

All of your speculation is based on the assumption that you are not getting but one pressure stroke. Have you actually checked your compression? With a gauge? If so what is it.

I am going to repeat the often heard cry of the China Bike Forum. CHECK YOUR VALVE LASH!

The most simpler answer may be that your valves are so tight they are not completely closing and no compression can develop. That can happen on both intake and exhaust.

[Mudflap]

It's also possible to have a flake of carbon get stuck under a valve so that it won't fully close. It's happend to me a couple times.

[krat]

It's also possible to have a flake of carbon get stuck under a valve so that it won't fully close. It's happend to me a couple times.

Very possible also, and goes right back to the nature of compression problems, they are usually valve related, bad rings, or a loose spark plug.

[oneb1jap]

Thanks s everyone for the input
The compression is 115 if memory serves correctly
Thay is why I figured carbon deposits on the piston.
Camera snake shows some; but not a lot.
I gave it dose of Seafoam spray to soak.
Have cranked it with sparkplug out & it turns fine.
Put in the sparkplug & seems to hit a wall most of the time.
Good HOT battery; new starter; checked the sprague over-run gear in starter
gear train; looked if water pump was jamming up.
Do not yet have the tool to pull mag/flywheel to check woodruff key.
One try out of fifty it might spark/run one pop. What is the valve lash spec.s ?
I can try again to adjust the valve lash - although I remember tightening to 10 thousants so could have chance of just enough compression to start - - knowing
burnt valve damage likely IF it would just TRY to run.
Have a trip planned so may be a while to continue this project.
Thanks much for the advice.

[J4Fun]

Seems to me either the spark plug is too long or you have valve problems, by what you stated above. Why else would it turn freely with the spark plug out. If the spark plug doesn’t show signs of being touched, then go to to the valves (more likely) but who knows. Thinking out loud here…

[oneb1jap]

thanks for the fast reply
have you any spec for valve adjustment?
no rush; am taking a trip, so this on back burner