TOPIC:

SO THIS GOES ON THE CAR, HERE IS THE LIST OF RULES,. I NEED TO KEEP TO THE RULES. I AM LOOKING TO HOW CAN I SAY EXPAND THE RULES IN MY FAVOR! doES ANYONE KNOW SOME TRICKS? IT IS VERY HORRIBLE AT START OF GREEN FLAG, AFTER THE FLAG DROPS SAY ABOUT FOUR LAPS IN CAR HAS SPEED BUT CANT CATCH THE LEADERS ABOUT THREE OF THEM ARE FAST FROM THE START HELP PLEASE....



The following modifications are the only allowed changes to the stock GX390 HONDA
CARBURETOR:
Throttle Shaft and dimensions
shown above.
A. Jet size is open.
B. No modification of shaft or butterfly allowed. Must be
stock shaft.
C. No grinding or polishing.
D. A pick up hole can be drilled parallel to the existing
hole of the same size.
E. Hole can be drilled in bottom of carb nut for remote
adjustment.
F. May remove tab on low idle mix pilot screw
G. Shaft size minimum .268
H. Shaft size between screws minimum of .145
I. Throttle plate minimum .036
J. No-go bore gauge .930
K. Gasket must remain stock Honda GX390K1/U1.
L. Carburetor insulator for Honda carburetor must be
drilled for pulse pump. Fuel pump must be pulsed from
insulator only. Only one hole is allowed. No air leaks.
M. No grinding, polishing or sizing of insulators or
adapters is allowed.
N. Emulsion Tube must remain stock unaltered length of
1.185 plus or minus .005
O. Emulsion Tube inner diameter of .100 and outer
diameter of .156 must remain stock unaltered
P. Emulsion Tube pickup holes may be altered – no tech
on number or diameter of holes
Q. Pilot Jet Holes – must have stock 4 holes but no tech
on diameter of holes

Hey Dice,
What have you done so far to the carb if anything?
If you haven't done #F the I would def. recommend doing so as all small engines these days are as lean as possible to pass emissions tests. Just don't try to remove the limiter cap on this carb because usually the jet will break off. Use a small "dremel tool" with a cutter wheel and just remove the tab so the jet will turn 360 deg. Open the jet about 1/4 to 1/2 round probably and it should take out any hesitation on start. As far as performance I'm not sure on a whole lot you can do. Just make sure the butterfly screw end does not stick out past the side of the throttle shaft..also if they've used any different screws or butterflies over the years..the thinner the better(anything you can do to reduce mass within the throat of the carb). Same goes for the choke shaft if u still have to run it.
Can you do anything to the engine internally at all?
Hope this helps

Hey 97,

Thank you for responding1 I have posted in several other small engines forums, go figure the first response and very wise one, comes from the gaming community! So Thank you to the creator of this site!


So far found out last week about the breaking of the tab, for the 360 deg of the jet. Will be checking out the rest of the information you left, and try to dial it in. Will let you know if there are results that show!

I think this might be on the right track!

I've been in small engine repair for over 15 years(only 31 now), and i raced go karts for a few years. Are you running pump gas(i'm guessing) or methanol?