Sm 250 cutting out at high rpm

[Niall-griffiths]

Hi all,

bikes a 2002sm 250 basically ec250"

ever since owning at full throttle high rpm in high gears the bike splutters then cuts out and restart the second I let off throttle
Also in lower gears I have a hesitation/stutter when coming on the power valve once again only at full throttle

if I hold the bike 3/4 just a little over it pulls very hard and won't cut out

I have tried a bigger main jet current 185 at the moment. and various needle clip positions

I have this weekend fitted a new piston kit but probally was there before and has been for years.also a new plug and air filter

here is a picture of my plug after a full days hard riding on road

the bike is completely standard, I removed the flywheel cover to find the flywheel has some rust and corrosion around it.

does this sound like a jetting issue or a spark?

 

[Cox76y]

Have you checked the level of your float?

 

[Niall-griffiths]

No I haven't I wil check this, are specs for it in the owners manual? I've noticed the bike doesent cut out and splutters alot less in colder weather, now it's 10 degrees higher than normal here it's got worse.

 

[Cox76y]

If you do a search on this forum or even on you tube there are plenty of videos and instructions on how to do this. I had this problem after adjusting the float level as I was dropping fuel whilst bike was on the stand. Anyway I adjusted it a little too much and it was starving for fuel at higher revs. A slight adjustment back the other way fixed it. It's a fine line.
Jc