88 honda 250x aftermarket carb question.

i picked up a near 100% bone stock 250x in almost mint shape inside and out. i found that someone had swaped in a kehin 38mm pe carb. side # dg8bbmi on the side of the bowl lip. it currently has a ajm top groove neddle / o4f 3.5 slide / 160 main / 50 slow jet / air screw from bottomed out back 3.25-3.50 turns. stock exaust is still on the quad.

i plan to ride trails here in ny/pa area and possible run a bit in the winter time . we are around 1800-2000 ft above sea level in my area. i would like to run prem 91/93 pump gas to keep it good and clean unless you have any other fuels that are good and dont cost 9.50 gal like i feed my quadzilla.

any help to make sure this is set up correctly would be great as its a ? ? ? bike as to history on my end. all i know is what i have found out. thanks and have a good day.

If the 250x is a 4-stroke then I would say that carb is way to big for that engine unless it has a lot of engine mods. Also it would run better on regular pump gas, compression on those units were around 9:1 stock.

I have that exact same quad that I just picked up. I have the same questions, actually. I don't know what the stock jet sizes are, but I am hoping to find out on here. It has a factory pumper carb, the same one that is on my '04 400ex, actually. Gotta love the parts interchangeability of a Honda..

Thats a 35mm Keihen Carb. 160mj sounds about right but the Pilot Jet to me is way to big. Start off with a 42pj.

here this is the way a 100% stock honda trx250x carb was set up


Purchase these jets from your Honda dealer.

Stock Main Jet Sizes: 300EX #122. 250X #125.

125 Main #99101-357-1250

128 Main #99101-357-1280

130 Main #99101-357-1300

132 Main #99101-357-1320

135 Main #99101-357-1350 (Typical Starting Point for Modified Engines)

138 Main #99101-357-1380

140 Main #99101-357-1400

142 Main #99101-357-1420

Stock Pilot Jet Sizes: 300EX #38. 250X #35.

38 Pilot Jet #99103-420-0380

40 Pilot Jet #99103-420-0400

42 Pilot Jet #99103-420-0420

Stock Engines with bolt-on Mods: Main Jet 2 sizes larger

than stock. Needle clip moved down one position. Pilot jet


Modified Engines with larger displacement: Main Jet at

least 4 sizes larger than stock. Needle clip moved down one




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