310R jet size makes no sense

[danimal95]

fimally got the 310 in the R and running very well has really good power and after doing a couple plug reads i have it tuned pretty well,however i noticed that it is only using slightly more fuel than my over bored and ported stock jug here is the combo the only thing that changed between the 2 is the big bore:

Krank-it racing 310 kit
klemm hand coned pipe from the 80's
dg silencer
38mm airstricker carb
stock air box with drop in K&N

the stock jug was running a 148 main jet
the 310 is only using 152 main jet

i think the problem may be 1 of 2 things the pipe is too restrictive or the stock air box and boot any help wopuld be appreciated

[ChrisD]

I went from a 190 main jet on a 39 PWK to a 175 main jet when I went from a 250cc motor to the 330cc. The larger motor has a lower velocity. It sounds counterintuitive, but it works that way. I would tune your motor to run correctly and you will be all set.

My top end motor mods for comparison to yours:

ESR 330 with TRX9 Porting
KX500 Rad valve with carbon fiber reeds
41.5 PWK
long rod motor
K&N
PVL ignition
PT Hi-Rev and Fat Boy silencer

Just make your bike run correctly and let the motor do the work. Don't worry about the fuel.

[danimal95]

thanks thta generally what i do,it just seemed odd too me that the jets are so small,but i guess every carb and engine are different,do you think i would benifit froma esr atc5 pipe?

[tecat-z]

Yep Chris D is correct. Dan, My buddies 330 that you saw at the dunes has a 39 pwk, and has a 172 main, 48 pilot, and clip in the middle. My 85 Tecate has more fuel delivery across the full range with a 38 A.S.:beer

[danimal95]

cool thanks guys,any opinon on the esr pipe??