It's sometimes happening on cold engine. Why? Carb is set aright. Crm is powerfull, works on all rpm's nice. But earlier when my crm shots, badge the piston rings and piston ending (no dimension). I don't ride a lot. How many km's should make it wossner piston in crm 250 mk3?

All other factors being correct, A wossner piston should give at least 10,000K of reliable usage.
Mike

sounds like a bit more fuel could be needed check your plug for colour if running exactly right it should be a nice brown colour

white/dry=to lean
brown=perfect
black/wet=to rich

could be a plug on way out if everything else is normal

It's brown, when i tank a little bit of mixture directly to the barrel across plug hole, she start first kick ever without shots.

Maybe reeds?

worth replacing if there old. any gap between the reeds and block is a sign of wear

I will buy new. What is best jetting for mk3 with full dep exhaust and boyesen reeds?

Oh dear..................

not oh fcuk
Mike

strangely enough this has started happenin to me the last 2 times I rode.. actually today I dint get out the car park..

las tues - decided to raise needle - and then startin it was a total be-itch! start - rough chuggy run.. cut out - BACK FIRE!

i took slide out againn and put it back it and went - and actually pulls like a mutha tucker now AR behind me was eating my roost again!

today tried to start - and same buggery trickery with back fires etc.. checked plug - looks like I am runnin well rich actually.. ( black plug! )

thought swop my pilot.. it was a 42 ( i only had a 38 not a 40 - thought I'd give it a go,, )

I was swoppin jets the lazy way - ie spin carb in the manifold / no need to wrench it out...

blinkin pin for the float pivot falls out,,... this benefits me - cos I have to fish out - take off sprocket guard - goog golly! one sprocket bolt is now finger tight! and hanging on by a prayer! also notice one engine mount bolt is loose as well

------> anyways I am thinkin the problem I was havin which may be the OP's problem? ----> is my pivot pin is loose - and this is jammin the float some how? ( las week I rotated carb to remove throttle an raise needle - caused the float to stick? no float action - no fuel - so then cutty out!

my next action is to remove carb from bike - give it a clean.. anyway to stop that pivot pin from sliding out so easy? or no worry abou tit?

stock jetting for Mark 3 is on here

http://www.crm250.com/specs.asp

not supposed to require jet changes for that exhaust I think?

u did swop the plugs? cos I changed mine and alls good again!

I check few new plugs, always same problem.