96 rm125 won't start

[therocket]

Doesn't start well or idle since son crashed. Pulled pipe and checked piston, powervalve-seem ok. Has spark. Son checked carb, and he said ok. Fuel is flowing, also.. Will bump start with effort. Flywheel seems to have some almost imperciptible movement. So, on the basis of work smarter, not harder. what steps should I take next?

 

[cr25096er]

it will bump start w/ effort? id remove the carb and clean out the pilot jet first. then take a look at the air filter. could it be saturated w/ gas? compression sounds low also.

 

[atc3434`]

I know this seems a little so simple, but have you tried a fresh spark plug. I had a situation once where I was I guess your would say, half fouled. The bike would run, but badly, and very hard to start. It had spark, but I guess it wasn't very consistent under compression.

 

[therocket]

I tried new plug, and it started after many kicks. When I put it on stand etc. to fiddle with airscrew, it wouldn't start again.

Will look at filter, and check carb tonight.

Any more ideas?

Think I will try a compression check before I pull the head, and check for damage.

I appreciate the feedback.
Thanks

 

[therocket]

Check list: work smarter.
filter very clean, compression seems to be about 115, max. tried two different guages--snapon wouldn't fit space very well, (frame tube in the way) and cheaper one which seemed to fit great--readings similar. Didn't do check carb again, didn't seem to be any point after these readings of compression.

About 5 hours on new rings. Above readings not what I wanted to see. Alas!

I will pull head, and..hopefully not too much damage.

I will let you know.

 

[therocket]

Took head off. Piston ring slightly frozen on exhaust side. Very little damage to see. No damage compared to the "piston diagnosis" sight that Eric Gorr has. Slight, very slight scuffing mark on piston side extending past the ring to the top side of piston ring. Looks like could have been a four corner seizure or an exhaust side seizure. Other damage caused when running bike after seizure of ring? Power valve doesn't seem to be protruding into the cyclinder. It was a unusally cold day on day of seizure so it might have been running too lean. Will take to expert and see what he says.

 

[RM_guy]

A four corner seizer like that indicates that the engine wasn't warmed up good enough before you ran it hard.

I like your work smarter approach. I've seen people replace the top end only to find ot that the filter was clogged. It sounds like you will need a new top end though.