hi everyone i took the crm out on its maiden voyage today did a few local easy lanes as the last time i did any green lanes was 34 years ago on my dt175.Anyhow the bike ran without fault until i had covered about 16 miles then the revs started to hang on a little while changing gear i pulled over and reved the engine and the revs were slow to come down to tickover but it didnt cut out its not revving its nuts off just like a high tickover which settles to a normal tickover i didnt touch the carb during the engine rebuild when i started it again when at home it didnt do it.i replaced every seal in the engine so i hope its not a crank seal issue just wondered if any of you guys on here have an idea.other than that she runs great and it bought back some good teenage memories for me.

first thing id check is the plug it could be running a bit lean and double check the carbs fitted nice and secure

Possibly the pilot jet has picked up some dirt, or needs a clean to get rid of any surface emulsion.
Another cause might be air is getting into the system, this is unlikely to be any of the afore mentioned routes, but could be from a tired rubber inlet manifold, check the clips are nipping it up correctly. Carry a small can of 3 in one oil, or similar, the next time it start this spray the rubber manifold area with the oil, if this cures it instantly, you know where the problem is.
The inlet manifolds to get old and start to breakdown, allowing un-metered air to enter the system.
It could also be the throttle cable hanging up, next time try twisting the bars side to side and see if that helps.
Mike

You're running a little lean. Try raising the needle one clip. If that doesn't work try two or get a larger pilot jet.

Thanks guys i will strip the carb off and take a look i forgot to say as well there was like a pinking knocking noise as well it wasnt bad but i could hear it now and again so i guess this points towards a lean mixture

CRMs are renown for a 'pinking noise' particularly the Mk2s. Not sure what it actually is but best guess is power valve rattle.

Took the carb off today and found that it has been jetted to a 135 main jet and the needle was one notch up from middle (needle lower than standard) it has a dep pipe and silencer should i put it back to standard jetting and needle height as i thought the dep pipe didn't need any jetting mods.the pilot jet is still standard
thanks

For some reason some CRMs do need rejetting with DEPs???????? Remind me - yours is a Mk2?

Beyond jetting there is of course air leaks in the intake system to be considered.

Check the plug for signs of weak running.
Is the filter oiled and clean?
Mike

the model i have is a mk2.2 the ail filter is new i will check the plug
thanks

took the carb off and cleaned it out at work in our ultrasonic cleaner.cleaned all the jets and its still hanging onto the revs so i messed around with the mixture screw and it runs alot better if i screw it out 3/4 of a turn instead of the 1 1/4 turn which it recommends in the manual im going to check the crank seal on the generator side just to make sure but everything is new so its just a stab in the dark it only hangs onto the revs when its hot

It's just a little lean. Raising the needle one should help. (putting the clip on one lower).

knackeredMk1 wrote:It's just a little lean. Raising the needle one should help. (putting the clip on one lower).

+1.
Also, what plug are you running?
How old is the fuel?
Mike

the plug is an NGK B9EGV Racing plug i cant find any reference to what models this plug fits i will go and buy another plug fuel is new what can you guys recommend for a decent plug
cheers

NGK B8ES is standard fitment and cheaper.