Got the bike back on the road after sorting the forks and the charging system, took it for a bit of a shakedown and noticed that it is missing/stubmling ever so slightly- its not massively jerky- you can just hear its not quite right- at about 4500-6000 rpm. its fine when you open her up- pulls well all the way to the redline.

Any ideas what could be causing this?

Anyone? Would be great to have something to go on?

What is your setup? carbs? airbox? flaps and so on?

Stock nc30 Carbs. Have been cleaned, balanced (on the bench using the drill bit method), slides drilled to 2.5mm, extra 0.5mm washer under needles and rejetted to 118/120, Blueflame end can. Stock airbox, flap is in place. New plugs, new battery, new generator coils, R6 Reg rec, new oil, filer and coolant.

Bike has done 16,000 miles.

try without washers I reckon. Easy to do and it is in that zone. Not all bikes like that mod

Im booked into a dyno on tuesday so hopefully this will help identify whats going on. I guess the washers would show as running rich in the midrange if theyre causing the problem?

yes - too rich at part throttle in the midrange - get a good graph on here!

Will do.

took it out tonight and did about 15 miles. Its definatley not quite right at 4.5-6k but still pulls really well everywhere else. Going to give it its first long ride tomorrow- 54 miles to and from work. fingers crossed it doesn't break down!

Well, she made it to work ok. Whoop whoop!

Well, have had the bike on a dyno this morning at SPR racing in Ruddington, Nottingham. They were great, very friendly, helpful and knowlegeable and fairly priced (£20+vat) for a dyno run.


Its running a little rich everywhere so have been advised to drop the jets 1 size all round and put a clean air filter in (mines not propper dirty but probably due a change!)

The stumble at part throttle seems to a charachteristic of the bike not liking low revs and be me being over sensitive- looking for problems! Have covered a good few miles in the last few days and its been fine.

The operator reckons its making healthy power and pulls nicely, figures a touch low but he reckons its not far off and given todays heat, humidity and my tired chain and sprocket would probably expect to see another 3 or so extra hp on the figure.

Graphs below:





Any thoughts?