Hi!

My nc21 has poor performance after passing 4k rpm.
I dont know what happened. something like can't breathe.

At idle it works ok, not hanging. all starts after passing 4k rpm.

any advices?

valve clearences?
main jets?

sorry for my bad english...

Did it suddenly start?

It's not likely to be main jets if it just start.

Electrical system (is battery charging?)
fuel system.. is vaccum pipe from tank to cylinders ok?

yes it starts suddenly...
battery charging ok.
vaccum pipe ok... i dont know what to do...

not likely to be jets then.

Was it standing a long time before the problem start? if it was not then carburettor problem is not likely.

Have you tested electrical system with multimeter? They are known to have problem.

Test the battery voltage at idle and at 5000rpm, with and without headlight

No it's not standing for a long time.
I test the battery tomorow... I have fitted bigger battery from a yzf r1 (jel) 10A. I dont do it right?

tragos wrote:No it's not standing for a long time.
I test the battery tomorow... I have fitted bigger battery from a yzf r1 (jel) 10A. I dont do it right?

the smaller battery is ok, the problem is usually the charging circuit stops working so the battery doesnt work properly

i still have tha same problem, and now not fairing at all..

no spark at any cylinder....

Are you using original battery still, what is the voltage.

yes i am on original battery now.
voltage 14.5v at 5000rpm, a litle bit lower at idle...

i found water in my spark unit!! i think thats the problem!

is there a way to fit a nc24(rh) spark unit to my nc21(rg)?

nc24 has 3 wires les than the nc21.

nc21 has a camshaft sensor.

tragos wrote:yes i am on original battery now.
voltage 14.5v at 5000rpm, a litle bit lower at idle...

i found water in my spark unit!! i think thats the problem!

is there a way to fit a nc24(rh) spark unit to my nc21(rg)?

nc24 has 3 wires les than the nc21.

nc21 has a camshaft sensor.

I dont' think you can fit it easily.. get an NC21 spark unit