Good morning from beautiful MN (USA). I have been diligently working on preping the NC35 racer turned street turned racer (again) for my first race season.

After race wire, race paint (see pics), spark plugs, and everything else I could think of I buttoned her back up only to have a slow drip from the fuel tap.

After a day of research I pulled the body work and tank back of, pulled the tap off and found that the vacum eliminator mod has already been competed to the tap but the phillips screws securing the three pices were loose enough to allow for the drip.

I got the tank back on for a test start and the bike held idle, and rev'ed with no hesitation. In fact I was very impressed with the throttle response as it sat up right on the stands. Body work went back on and I suited up to test ride the bike and scrub the tires in.

I placed it in gear and rolled out onto the streets only to find the bike in every gear was having trouble under wide open throttle. Actually it sounded as if it would run on just 2 cyclinders!

I'm racking my brain thinking of the potential causes for this but need your help.

Here's what I know...
the bike may have some loose chunks of paint (overspray) in the tank but nothing too small that woulnd't be caught by the fine mesh of the fuel filter.

While in gear, I can clutch the bike and rev it with no problems or hesitation but when I let the clutch back out and give her gas it boggs down and sputters.

The bike was fully warmed up as the previous owner eliminated the choke from the carb set up so don't chalk it up to a cold bike.

The air filter eliment is installed and is clean.

I went through the entire bike and all ground wires are in tact and fastned down tight.

It boggs down in every gear above 6k or anytime I open the throttle all the way.

Please send ANY advice to the follwing email address so I can read it on my Iphone outside immediatley. PLEASE HELP!
kurtsplanning@gmail.com

I doubt ur still standing outside so il post here.. The bike will rev quite freely on 3 cylinders, but you can tell the difference on 4 and can feel the exhaust thats not firing. Do the usual plug checks and clean them thoroughly, then check for spark on all plugs. Did you fit that maggot can? the exhaust flows rather a lot freer with that, so you might need to richen up the mixture. The colour of the plugs will give an indication of the mixture.

Otherwise take the carbs off and blast passageways out with carb cleaner. these spluttering fueling issues, of which there are plenty on this forum, usually due to carbs not running right or plugs fouling/flooding

U said it revvd with no hesitation in neutral, but at the same throttle opening in gear it spluttered?

Are you sure it's not the limp-home mode kicking in because of electrical issues??

When the speedo is removed or the appropriate wires fiddles with it will cut spark to 2 cylinders above 5500rpm. The bike will still rev freely with the clutch in even on 2 cylinders.

Simple fix to see if it is this: Find the orange/blue wire that goes to the cdi, splice an extra wire into this (don't cut anything) and run the other end to the battery +ve.


I would check this before looking at anything else.

Deffo sounds like restriction circuit has been unplugged and omitted from the loom. Either mod the loom with the resistor (as mentioned about a million times around the forum) or replace the speedo board to the loom.
bet that sorts it

+1 on the speedo removal restriction.

cuts to 2 cyls at 5,5k revs...