KR-1S.co.uk Forum

Newly rebuilt and newly run-in engine broke down on me, first lap first session on a Donintgon track day last week.

I'd ridden it on the road a few times but this was the first time I'd ridden it full throttle in anger.

On full throttle the revs totally bogged down, then it cut out. Got recovered back to the pits where it kick started again. Seems fine at idle - just not healthy under load.

Any ideas? Would it be a fueling issue or spark? Or both?

Any help would be appreciated

Thanks!

Sounds like a fuel issue to me, like your carb jetting set incorrectly.

What can you tell us about the jetting and have you made any modifications to the induction?

Ditto Luders - sounds like fuel starvation.

Kinked fuel line ?
Blocked fuel filter ?
Perforated vaccum pipe / diaphram ?
Tank breather ?

Good luck !!

Cheers guys.

The jets are unknown. They're whatever was in there when I bought the bike (2 years and just 100 miles ago!)

I've put two new inline fuel filters in.

But the first time this happened I found the vacuum pipe had come off the top of the carb. I fixed it back on, but it still happened. I'll check the diaphram.

If nothing has changed with your jetting or induction, check Tambo's suggestions.

Also check the air filter. There was an instance where the filter cage was broken on someones KR and at faster revs, the air filter was being sucked down into the velocity stacks in the air box, causing it to bog and not want to rev past 7,000 rpm or something like that.