Everyone Help, Please...

[KP's lil'300]

ok from the top, i have put a pro-circuit t-4 slip on on my 300ex. i also installed a dj124 main jet with the new needle and the E-clip down on the 3rd notch(on the needle), also i have a k&n filter and outerwears cover with the airbox lid On. i did everything the way the instructions said, but when im in 5th about 3/4 throttle and let off the gas it kindof has a pop to it, not like a loud backfire but kindof. please tell me what you think is the problem, thanks in advance, and any answers will be greatly appreciated. thanks again. KP

The exhaust popping on deceleration you describe would suggest a lean condition on the main jet.

Try going up one size on the main and see what happens.

If you had installed a new plug it could help out also.

[WYO330EXRIDA]

don't do anything, nothing is wrong
your just running a little lean and that is a good thing
I ran mine really lean for a long time until I put more motifications on and nothing bad ever happened
you don't want to be too lean, but the minor popping sound is ok
Your probably running just the perfect mixture for performance

[KP's lil'300]

thanks but i heard both sides and i sure dont want to screw anythin up. so i would like to have even more info. thanks to the both of you. KP

[Houser Cannondale]

the popping sound on deceleration is not the main jet, it only functions from 3/4 to full throttle. i wouldnt really worry about it if its a light popping then thats normal.. but if it backfires alot and is very loud then you are probably too lean. if its too lean when you let off you could try increasing the pilot jet or changing the needle.

I am not claiming to be a jetting genius but when I went from a 160 to a 168 mj the popping stopped. Its a little too rich now and I do need to drop down a little but would you believe that I have been to like 4 diff dealers and they dont have anything between these two sizes.

[Sparks425Ex]

If the dealers don't have then then they can order them. They will get them in like 3 days

[Houser Cannondale]

i jetted my 300 it has a fmf powercore 4 pipe k&n filter and no air box lid i jetted it exactly how k&n jet kit says and it runs perfect alot of power and doesnt bog but it still pops sometimes lke you said revved in 5th gear and you let off i think they all do that a little sometimes.. but its a very small pop not real loud. i think its normal.

[KP's lil'300]

okay thanks, you all sold me on leaving it the way it is. a BIG thanks to all of you who replied. KP

revved in 5th gear and you let off i think they all do that a little sometimes.. but its a very small pop not real loud. i think its normal.

What you describe here seems borderline and not the type of deceleration popping or backfireing that I have had in the past. Last winter (remember the air gets denser when its cold and makes things richer) my quad would sound like a popcorn machine everytime you let off the throttle from any rpm or amount of throttle but was the worst from full WOT. With the air box cover on it was much less but still was doing it. The quad did run strong and once the weather warmed up it was almost gone but not completely gone till the main jet was changed.

Just my recent experience.

[Houser Cannondale]

(remember the air gets denser when its cold and makes things richer)
sorry to tell ya but the colder it gets, with the same jetting your actually getting leaner. think about it, denser air means more oxygen per volume of air. plus you have the same jetting so actually it leans it. thats why you have to use the choke so much in the winter, because the bike is leaner than usual. also when you put the airbox lid back on, you were reducing air flow thus richening. thats why your popping wasent so bad after you put the lid back on.

oops my bad, had that backwards sorry. :o

[josh]

i'm gonna back up kenny on his post, I just installed a full cobra exhaust on my bike and it started to pop cuz the bigger header makes it run leaner, so i went from a 122 main to a 130 main and presto, no more popping, and i am running a 1991 250x, i have a unifilter and holes drilled in air box, rest stock. the only true way to jet a bike is to keep trying new things till it feels like it is running at peak, and it also depends on what type of fuel you are running, if you are running any pump gas you would have to jet it larger than if you were running race fuel, or 100+ octane, every single bike is different from the elevation to the heat of the air, so just keep playing with your bike till it's fine

[josh]

personally i would try goin one step up on the main, and putting the e-clip back on the 2nd notch and leaving the air box on, put a new plug in and go for a ride for a little while, when you get back check your plug, if it is really dark and grimmy you are too rich, it it starts getting white, too lean, the spark plug is the best indicator when jetting, you won't hurt anything by playing with it, it's actually better to run a little rich than too lean, cuz then you would prob just foul a plug at the worst, but play with it and check your plug, that's the best advice i can give you.

josh