jetting

[H_A_M]

ok just wondering where to start with my jetting on this quad. it is an 88 250 i think the main is a 270 rite now. it is ported and has a shaved head the rest is stock. this week i am adding fmf fatty pipe power core silencer boyseen reed petals and putting some holes in my air box with a hole saw and covering them with window screen to try to get it to breath better. im on a pretty tight budget also wondering what you guys think i should be running for gearing i have 11 front rite now and stock rear i also have a 13 and 12 tooth front whut kinda bike do you think this will stick with now i have no prob with warriors 400 ex's and z 400's

[rap720]

I run a ported 87 cylinder, dynoport large volume pipe, 38mm TMX carb, and a clamp on filter. My main jet is a 300. It always best to start on the high side for jetting. just remember that the main jet is only used from 3/4 to full throttle. the needle taper and clip setting have alot to do with 1/4 throttle to 3/4 throttle.

[CR480R]

Originally Posted by H_A_M

what you guys think i should be running for gearing i have 11 front rite now and stock rear i also have a 13 and 12 tooth front

I run a 13/42... It pretty good all-around with 20" tires... I would try the 12 tooth(stock)first if you run 22" tires and see how you like it... The 11 tooth is too small IMO and also wears the chain and slider out faster....

[lt250racer]

I am pretty sure that the idle jet has to do from 0-1/4 throttle & main jet has to do with 1/4 - full, you really dont need to change the needle or clip position unless you move elevations greatly or you switch the carb to another bike and your tring to jet once again to this different engine. I am running a 63 pilot jet and 158 main jet with my mods and the plug looks great.

[rap720]

Originally Posted by lt250racer

I am running a 63 pilot jet and 158 main jet with my mods and the plug looks great.

you are running a keihen carb, He said that his carb is stock so it would be a mukini. Keihen and Mikuni use two different metering scales for jet sizes, A 158 main would be way too lean on a stock lt with a mikuni carb.

http://www.iwt.com.au/mikunicarb.htm

look at figure #'s 2,3,4,&5. this is exactly what is listed in a mikuni owners manual.