Hi. My nc29 race bike is giving me a hard time. It runs fine below 5k revs. As soon as you hit 5k onwards it only runs on 3 cylinders. Changed the plugs. No.2 was slightly different colour to rest. Got spare coil, leads and cdi. Nothing helps. Any suggestions?
I'm meant to be at knockhill on Saturday and my mechanic (husband) is going to be away all week with work.

Hi Christine
I had a similar thing on my NC29 race bike but the other way round i.e. would run fine higher up the rev range but only run on 3 at lower revs. Turned out the pilot jet was blocked on one cylinder. I would guess its a blocked main jet in your case.
Good luck with it.

yes,carbs sounds like they could do with a clean out..

Carbs have been cleaned to within a millimeter of their life! Could it be a wiring issue?

Hi Christine, have you cleaned the actual main jets as that could be the issue if one is blocked?

Had all the jets out and cleanex

Hmmm weird! Are you running stock sized main jets?

I've figured it out!! I was googling stuff and I kept coming up with stuff to do with the limiter wire. I've piggy backed the orange and blue wire where it comes out of the cdi and tried it connected to the positive terminal on the battery. And it seems to run fine. So I'm guessing the wire must be broken somewhere along the line.

Nice one, glad you solved it. [emoji2]

Result!