New Exhaust, stuttering revs

davez · 08-23-2009, 7:55 AM

Sorry for the title, couldnt think what to put.

What it is, I have fitted a new set of pipes of the 4-2-1 variety, these have a slightly larger diameter down pipe. I have noticed, with or without the new end can I also bought, that at 2 1/2 thousand revs I get a stuttering, as if running low on fuel. This only happens at this rev range, noticed mainly on slow corners, speed humps and city traffic where the bike goes into jerky mode. Ok its easy to stick a couple of more revs on but it a pain when it did not do it before. Any ideas?

ghbzorro · 08-23-2009, 8:02 AM

Shim the needles up a hair. New pipe is and can is resulting in a lean condition at those revs.

davez · 08-23-2009, 8:33 AM

Ok, thanks for the quick reply. By shiming up a hair do you mean raise the needles to the next level? sorry not very techie when it comes to carbs.

speed demon · 10-10-2009, 11:53 PM

i just wanted to ask if removing the end can will harm the bike ,, it is extremely loud , i like the way it sounds but back pressure issues i cant really now for sure if they cause harm

Surffrog · 10-12-2009, 3:07 AM

Quote:

Originally Posted by davez

Ok, thanks for the quick reply. By shiming up a hair do you mean raise the needles to the next level? sorry not very techie when it comes to carbs.

I'm not sure you can shim the 400 needles the way you can with the bigger bikes, but you can always put a slightly bigger jet in. Alternatively, give the mixture screw (located at the bottom of each carb when attached the bike) a 1/4 turn to see if that helps.

N.B. It would greatly help accuracy if you take the carbs out to do this.