help with fcr 39 jetting for newbie

hi guys i have a drz 400sm and i recently got hold of a fcr 39 carb the slant one from a ccm 404 as i was so excited to fit it i put it straight on the bike and it run ok but if i snap the throttle back when the bike is at low rpm it nearly kills the engine. I'm guessing from reading up about them it could be the jetting but i believe the ccm has the same engine so is it that?


also can anyone point me in the right direction to buy the jetting i need, I'm in the uk.

my bike has standard head pipe small sm one and open race exhaust, sea level.

any help is much appreciated guys thanks.

i gave it a read, so it is only the leak jet that would be causing the problem so I'm guessing that all other jets are correct if the bikes running ok apart from that bog from low rpm?

would you know what size jet i would need to try next and where can i get it from?

also it says about adjusting the timing, the carb i have isn't the mx one and i don't remember seeing a adjuster for it like the one shown in the pics.

is it possible to adjust this on the slant body?

i don't have a leak jet in my carb. I've lost all hope on fixing this fcr, so bad that going back to the makuni if can't get this bog sorted. 

it doesn't even seem any better so before i throw it at the wall can anyone tell me how to sort this out?


it runs fine if I'm just cursing around but if i wanna go fast it just runs like crap

There is a write up in the WR450 forum regarding the Bog with the FCR, sticky FAQ at the beginning of the forum. 1/2 is about the MX version, the other half, written by TTer JNcola is about the slant. Read his part many times BEFORE you do anything.

i have done the mod where you wire the ap arm up and cut down the stopper and it solved my problem. I'm really happy with it now

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