Some help needed please

[keithvfr]

My mate bought a NC30 but it has a problem.Was running ok when he 1st got it but not now.
Bike wont rev over 8,000
And when it get hot it dies and wont restart till cold.
Already checked the coils,Plugs and leads and the cdi.
Also took the carbs of and stripped and cleaned them.

Starting to run out out ideas what could cause this.

Any help or ideas would be great thanks.

[MexicanGringo]

does it not rev over 8k only when hot or all the time? Are the plugs new?

[CMSMJ1]

is this when revving it in neutral or in all gears?

Are the carbs definitely seated properly and have the right jets in? Diaphragms all solid and no tears?

Does it run on all 4?

[keithvfr]

Plugs are new ones i was going to put in my nc30.
It revs upto 8k freely then wont go any further no matter if its hot or cold.Its all the time in gear or neutral.
It runs on all 4 all the time and the spark to each is good.
As far as i can tell the carbs seem to be sealed ok but might take them back off tomorrow and make sure or could try mine in place of them.
Someone suggested that it could be the baffels have collappsed in the can but as its a standard system then i cant really take the can off easily.
Think it must be something with the carbs.
What size jets should be in them for a normal system?

[CMSMJ1]

with a brand new airfilter you are wanting 115F and 118R jets.

If you have the airbox off it might struggle to rev out. If it is a K model - 1989 - then it might have 112 jets and so will be lean..but should run nicely.

[Neosophist]

Jap import? is the speedo sensor connected properly? If that isn't working right the biek will start to miss afer 5500rpm.