Hi Guys
I have a NSR MC21 i build it my self but i have a problem with starting the bike
If the bike is cold it wont start but if i spray in the curbs starts and runs ok but if it cools down wont start, i clean the curbs a check the reeds
for cracks the look ok, can anybody give me some help or guide me to find the problem i have 2 sets of curbs but is the same with both

I hope someone can help

Thanks

Leaking crank seals may be a real possibility. Did you do a leak-down test after you rebuilt it?

I have the same problem with mine and I just wasted some good money on it as well can't kick start it when it's cold so I have to push start it till it turns on just to warm up the bike but its still takes a while to push start after its warm it kick starts quick but if I leave it off till it gets cold I have to resort to push starting it again its pretty frustrating and unreliable seems like mine has the same problem as yours I hope you find a solution for yours and maybe this topic you made could help me with mine

Sounds like the pilot jets may be blocked if it fires up after spraying.

This happens to a few bikes, mine included. When cold the lower cylinder won't kick in due to the leaky seal. Once warm, when there's some oil around it's OK. Crank seals - search the threads for this topic.

Hi Guys i think i solve the problem i think it is the curbs i found a set o curbs from my MC18 and put on and the bike starts no problem
now i have to find the problem with my MC21 cubs
Thank you all