Bought 250EX W/B E-series kit, what main jet should I use?

[Jason69]

My White Brothers E-Series kit is on the way from MOTOWORLD. For $269.00 + Shipping ($285.00 Total) they are sending me a W/B Slip-on, K&N & Outerwear. It doesn’t come with the Jet Kit though. That’s another fifty bucks… It’s my wife’s quad so I don’t want to spend much but I do want it a little faster because sometimes I get stuck riding it when I swap with my wife or let my friends (without bikes) ride mine.

I want to remove the lid so I know I’ll have to re-jet. What is the stock Main Jet size? What Main do you recommend? And do I need to move the needle clip up or down, Or do I need to buy a new needle? We live in CA and we mostly ride under 3500 Feet and we are also planning a trip to Glamis Easter weekend, so we need to get her some paddles. I don’t want to get stuck with her bike and not be able shoot some hills.

Thanks

[Jason69]

???

[brokeitin3]

I would say going up 2 to 3 sizes from the stock #95 will do some good

[Jason69]

Thanks, So if stock is a 95 then i can call honda and get a 98?

[Jason69]

Help

[brokeitin3]

i think it goes #95, #96, #98, #100. So the #98 or #100 should take care of you if the pipe is the only mod. You can also use the disk on the end of the pipe to tune it a little also.

[jmoney45]

We have an fmf slip on with a k&n filter, but still have the airbox lid on. I put a 97.5 main in and it seems to run good, maybe even a little rich. If you are removing the lid I would try a 100. I think the 250ex comes jetted rich from the factory.

[250exen]

i have a t-4 slip on and a k&n filter with out my air box lid and im runing a 107.5 main.... its running good too.

[Jason69]

What is the stock pilot? I want to change it. My wile usually isn't on it full throtle so i think the pilot will help her out. What should i change it to?

[Jason69]

I put a 108 Main Jet, it still backfires on deceleration, so i backed out the fule screw a turn and it helps espically when i put the lid back on but i like to run it with it off. Any other ideas? should i try a 110?

[White_Knuckles]

You need no more than a 102 for the main below 3000 ft. Airscrew out 2-2.5 turns, adjust for best idle. The backfire thing is common with low back pressure and quick throttle release.

When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.

The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.

Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there. The exhaust then pops or backfires.

[Jason69]

Thanks for the great info, that sounds great, Would a larger pilot help this?

Is that why Duncan Racing changed the pilot on their 250EX in a recent DirtWheeles I think it was them, it was Four Wheel ATV ...

They did some hop-up's to a 250EX and one of the things they did was change the system to a Fat Boy 4 a 110 Main & a new pilot, but i cant remember which one?

Thanks again

[White_Knuckles]

Yeah, you could try going up to a 40 pilot, stock is a 38. Some have raised the needle by lowering (going toward pointy end) the e-clip a notch effecting mid range richening.

To totally eliminate backfire is voodoo some claim success others keep dinking around. Keep a close eye on plug condition and experiment. Remember when the weather gets warmer it may all change again so don't go too nutty now.

Also richer is better then lean, Honda ships on the rich side so don't drown the poor little thing hittin' it with a fire hose for 1 HP.

Good Luck