KR-1S.co.uk Forum

Well, after riding my KR250 for the past week, I've noiticed that it runs out of breath after 9500rpm @ WOT.
At about 3/4 throttle it pulls evenly all the way up to 10,500 confirming my thoughts that it's most likely an intake restriction. I'm not quite sure if the restriction is in the carbs not being able to flow enough, or maybe it's the airbox holding it back.
The barrels have been ported, which has of course increased it's appetite somewhat.
Any ideas people?

so : with 3/4 throttle is goes all the way to 10.500, and full throttle only to 9.500

Sounds like it could be dirty carbs and jets that need cleaning out or replacing

JanBros wrote:so : with 3/4 throttle is goes all the way to 10.500, and full throttle only to 9.500

Sorry, I should have explained it better....

It will rev to 10,500 @ WOT. But, HP drops off @ 9,500 and while it will keep revving, you are better off to grab the next gear.

Clogged filter?

Just that mine had half the fluff from the tumble drier in it , i never cleaned it for 3 years .

you been down gibsons since you fitted your filter cliff?

The filter is fine.
I really just want to find out if anyone knows if the carbs or the airbox are the greatest restriction on the intake side.

If carbs, I may see if I can get the 28mm stock Mikuni's bored out to 30 or 32mm. I also thought about getting some 32 - 34mm RGV (or such) units, but then I need to make the cables fit somehow, and the carb rubbers would be near on impossible to change.

If it's the airbox, the only options I can think of are, Larger opening in lid (have spares, so may try this anyway), Or remove filter for a test run to see if it's unable to flow the required air, Or if all else fails, ditching the airbox and fitting pods (although the consensus seems to be that strokers prefer an airbox, so very wary about doing that).

So..................

mr_bungholeo wrote:you been down gibsons since you fitted your filter cliff?

Not yet Darren.
If you go again i might tag along if that's ok?