Could anyone shed some light on the problem I am having with my 16000 mile nc35.
When I bought it last September it had a flat spot at around 6000 to 8000 (stuttering and spluttering) so I have been giving it a full service over winter.
The two tube exhaust gaskets at the bottom were leaking and so replaced.
The valves were checked and re shimmed (all inlet valves tight).Carbs cleaned (not balanced or set float hights though)
Plugs,oil and air filter replaced.
The problem now is that the flatspot has moved up the rev range and now starts to show itself at 11000 and wont rev past 13000 while riding but will when revving.
when on the motorway at a constant throttle 10-11000 the bike jerks and stutters untill you close the throttle slightly then it smoothes out
The bike has no restrictor washers and has the standard exhaust and has a good fuel flow from the tank.
Any Help would be appreciated.
cheers Ste.

as you have said anyhows, balance and clean carbs first, set float heights and see how it goes, at same take note of your jet sizes in case that is the next step


david
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Check battery voltage also at midrevs, it should be over 13.5v.

Check all of the earths also.

p0gue-mahone wrote: The problem now is that the flatspot has moved up the rev range and now starts to show itself at 11000 and wont rev past 13000 while riding but will when revving.
when on the motorway at a constant throttle 10-11000 the bike jerks and stutters untill you close the throttle slightly then it smoothes out

cheers Ste.

I had exactly the same problem, and it wasn't until I rejetted 112F 115R, and one extra 0.5mm washer on the needles did it go away and rev cleanly through the entire rev range under load.

Thanks for the replies. :D
I have checked the voltage at the battery and with the lights on the figures are 13.85v@1500 rpm-12.75v@5000 rpm-in the red@12.85v
with the lights off its 14.34v@1500 rpm-13.65@5000rpm-in the red@13.50v
The lights are permenantley on so I have just pulled the plugs from the headlights.
Do these numbers look ok or would I need to change the rec/reg?
I will hopefully strip the carbs again this weekend and look at rejetting as I have just purchased an Art exhaust off ebay.
Does anyone know the jet size I would need with this can and where i can purchase them?
Cheers Ste

Your voltages look fine.

I had to up the jet sizes after fitting a Scorpion endcan to mine, so I guess 112/115 wouldn't be a bad place to start. Any motorbike shop with a dyno will be able to sell you jets.

Problem solved.
I bought a 2nd hand set of carbs off ebay,Re-jetted to 112.5 and lifted the needles with a 1mm washer.
I also balanced the carbs with a 1mm drill bit.
The bike now pulls cleanly through the rev range and into the red :D
Result.