engine 'knock'

Luke Davey · Post by **Luke Davey** » 06 May 2003, 10:09

hi guys, im new to this fourm
i have a mk3 crm250 with 20'000km on the clock.
i little while back the engine developed a 'knock' when engine speed is decreased, it sounded like piston slap, but the engine has not done alot of work, so i m not to sure about that. i talked to leisure trail uk and they said to ride it till it smokes excessivly, or the engine becomes too hard to start. any ideas
ive removed the expansion chamber, and looked into the cylinder. i can still see the cross hatches from the factory bore.
i have checked everything that i can without pulling apart the engine, and all seems well.

any help, or suggestions would be appreciated

Bargos · Post by **Bargos** » 06 May 2003, 15:27

Luke

LeisureTrail usually know what they are talking about when it comes to these bikes, have you looked at any of the other posts concerning engine noise?

Whats the oil consumption like on yours?

Luke Davey · Post by **Luke Davey** » 07 May 2003, 01:43

the oil consumption seems ok, but with an auto lube system, it is hard to tell. any other possibilities

Bargos · Post by **Bargos** » 07 May 2003, 08:40

Hi Luke

Does it make the noise in all gears, at high or low revs? Please try and be a bit more specific.

Some of the other CRMers have reported balance shaft wear which manifests itself with a noise from the crankcase - see some of the other posts for details.

I find my MK2 quite noisy as well but intend to keep riding it until something is obviously wrong or it wont start.

wreckedpete · Post by **wreckedpete** » 07 May 2003, 11:45

Twostrokes are typically noisy when engine spinning down from high revs. It's a buzzing rattle, not a knock. I noticed a metalic rattle, almost a sqeek like a chain without any oil when slowing down in gear with a VERY loose chain! It was where the chain rides off the front dive cog slightly. This is only when the chain is very loose (do not over tighten it)!

Luke Davey · Post by **Luke Davey** » 11 May 2003, 07:34

thanks for the replies

the noise is low to mid rpm, and when the engine is under load.
it sounds like the noise some of the other guys are hearing.
what do you mean by balance shaft wear, in the gears, or the bearings?
i will check the balance shaft next time i have the engine apart

cheers

wreckedpete · Post by **wreckedpete** » 12 May 2003, 10:50

See entries under 'Strange Noise': I now anticipate its the power valve. It rocks slightly when lowered at tickover/low revs, so the metal slider clatters against the barrel chamber. This can be checked with front section of the exhust pipe removed, reach in to touch the bottom of the slider and attempt to rock the slider with your finger. Apart from the simple timing check I've not messed with the power valve, can this play in the slider be adjusted out?

engine 'knock'

engine 'knock'

oil consumption is ok

at low to mid rpm