backfiring

[FMFracr287]

Hey, i just installed my new Procircuit T-4 silencer on my 250EX yesterday. I noticed that it constantly backfires. Well i think it is the sparks hitting the spark arrestor. it is very annoying. i was wandering if its just doin this cuz it is brand new. Pleeze help!

[JB's 400ex]

I have a feeling you will need to re-jet.

[DaveEX7]

definately rejet, and make sure who ever does it, does it rite.....

cause my friend had another guy who they trusted put them in..... now the pipe actually makes the quad slower cause his jets were offset


dont worry my friends pipe did that all the time when he was coastin down hills or when he reved it up all the way or alot

[FMFracr287]

How will i go about doin this??? will i need to by like a K&N jet kit

[DaveEX7]

yup, k&n or dyno jet or dial-a-jet

ur pick..... but getta stage 2 jet cause the stage 1 is a waist of money

[FMFracr287]

OK thanx for the advice

[optikid123]

all jet kits r a waste of money. just get the bigger jets u will need from a shop

[DaveEX7]

Originally posted by optikid123
all jet kits r a waste of money. just get the bigger jets u will need from a shop


thats true, they should give u some $5 jets when u get the pipe

[Newbie400ex]

Definately lean. Mine did the same thing. Go up a couple jet sizes. Jet kits work pretty good for experimenting if you don't really know what you are doing. I have a WB e-series,K&N,Modded airbox lid, and DynoJet DJ170. Works great.
:cool:

I dont know how bad your deceleration pop or back fire is but I do know its damn cold out and that is leaning your mix a whole lot.

See how bad it is when its a little warmer say like 45-50 deg and then you will have a better guage for the temps you will be doing most of your ridding in. Dont keep running it if its still popping a lot cause you can do damage to the piston.

When you decide to go larger with the jets just get the next couple sized larger than stk and see how they work, and you will save a lot $$$ over the jet kit. And dont forget its not just the main jet that needs to be set up.

HAve fun jetting is a blast

[dariusld]

You can also make sure there are no exhaust leaks, especially around the head. This will cause a backfire.

[fuddrucker]

If it still does it after jetting, try replacing the head pipe gasket. Only costs a couple of bucks. This is the part number..."18291-MV9-000 GASKET, EX. PIPE" and usually should be replaced when you remove your pipe.

I don't find a jet kit a waste of money..Traveling all over the place,,weather changing..running different air box setups at different times...It's nice to have plenty of jets on hand..

[JB's 400ex]

I don't think a jet kit is a waste of money either. You are just paying for someone else's testing and knowledge. I wouldn't buy one myself because you can probably save money by just buying a few jets and doing it yourself, it's not that hard. My local shop will took back the jets that I didn't use after I rejetted as long as they were in perfect condition. If you just put a slip on exhaust on you will probably be just a few jet sizes off. They are only like $5 so just buy a couple jets, go up to the highest one and try it. I will say that with mine it does pop and backfire in this weather(cold), when it warms up a little it runs perfect. Unless you do your majority of riding in the cold winter weather I would do your testing in the summer. I am sure you will still have to rejet though.

Well the major reasons I dont like the kits (K&N or dyno) is you dont get the Keihin jets and the Dyno jets dont flow the same and you pay for a lot sizes you dont need.

I have been able to pick up Keihin jets as low as $3.00 ea and I have not seen a kit anyware near the $12.00 to 20.00 you would normally need to spend to get a good range of sizes.

[DaveEX7]

Originally posted by 440EX4me
normally need to spend to get a good range of sizes.

ya, like $50 some of them are

[330EXman]

you are running lean

dont run that engine again till you rejet

running lean is very bad afor a engine and causes it to heat up and do many damages

you need to let more gas in cause now you are flowing more out with the exhaust

rejet and allow for more gas to enter