still backfiring during decelleration....

[Ddw350]

my 350x is still backfiring during decelleration,ive been told to turn out the air screw an extra1/2 turn but it still does it .i havent turned it out any more,i wanted to get some feedback first it has a k/n filter,1"holes in top of airbox and a supertrapp,with a #138 main jet...thanks for you input.....oh yea,i wont be riding and tuning for the next few nights ,last night it was 12 degrees,tonight its supposed to be 8!!

[plkmonster2]

yeah, its been cold here to, it was -16 one night, then it went to -8 now its 8, still too cold, and we have about 1 1/2 feet of snow here. It sounds as if the timing for the spark is too advanced. it could be the mixture being too lean, and detonating on rapid deacceration, but i belive it could be the timing. it seems ok on acceleration because the spark is always trying to catch up, but when you slow down, the spark is ahead of the cylinder. im not sure on a 350x, but it the timing can't be changed, then id think that it would be too lean. our lawn mower pops bad when you lean it too much. also, i would think you would turn in the air screw? im not sure, but the less air for a lean mixture seems right.

[200xman]

Raise the needle in the slide 1 clip up. Worked on my 200x and 350x with basically the same setup as yours.

[sittinguy]

Chaeck the slip joint between your headers and you pipe, if I is leaking alot there it can cause backfireing, also repack you pipe or remove a few of the disks from your supertrap, to increase the backpressure and sometimes that will cure your problem. I am surprised you are useing the stock 138 jet still. One of my X's that is mildly built has a 140 in it and in the wild one I have a 152, and it runs great

[J.D.]

Most likely it's just an exhaust leak.....

[samster143]

If opening up your air screw a turn or so is no help, I would start looking for the next size pilot jet. You may want some more opinions but that is where I would look next.

[nate b]

i'd say its something to do with the exhaust

[AirManCam]

Is it an actual backfire or just little pops? Is it a stock pipe or no? All of my wheelers make a small pop when you decell. Its just normal if its the little pops. Besides it makes it sound cool :D

[Ddw350]

its not an exhaust leak im sure of that.when i had the #140 jet in it hardly did it at all,but it never seemed to run right,always rich,so i went back to a 138.it runs great,just "pops" several times on decelleration[little to medium pops according to airmancam].200x man..ill try that with the clip on the needle.im gonna try the airscrew trick a few more times.i think factory is a turn and 3/4?i,ll have to look in my manua.then ill go from there

[AirManCam]

Ill have to record what I mean. I mean say when your going down the road in 6th gear maxed out, and you let off its normal for little sounds that sound like baw baw baw bap. If they are the same sounds they are just from the tires going to fast for the gearing,and the motors trying to slow it down. Im pretty sure that that may be what your talking about

[olive123]

i dont think you want to put the clip UP one. thet leans it out. you want to go DOWN one. the clip position works from 1/4 to 3/4 throttle. If you are in that range with the popping it could be the lean mixture and one clip down might do it. it would be the easiest thing to try. Make sure you read the plug.

[samster143]

How would you "read the plug" for the midrange throttle position?

[86250RZ]

Let me know if you fix the problem, my brother is having the same problem whith his 86350X.

[hondajas]

Bunch of wimps, around here in Manitoba, three nights ago with the wind chill it was -58 farenheit, or -50 celcius, and yeah I went out snowmobiling. Now it's hot out, it's -13F.

About the backfiring, I have no idea, but it did happen on my big red anytime you'd let off the throttle.

[HemiChallenger71]

I'd recommend a 140-142 main jet that'll fix you problem. Running a little rich isnt a big issue. I wouldn't recommed messing with anything on the carb but that main jet with your modifications. If the problem persist after changing the main jet then turn the air screw in 1/2 a turn. If the problem still persists jsut ride the damn thing. You have to test and see what works best for you as well. To change the main jet on a 350X is easy. Turn off the fuel, and let it run untill it stalls, then pull the drain plug for the carb, and the main jet is right there. You need a shallow well 6mm socket to get it.

I had a stock 86 with a cobra silincer and k&N filter w/outerwear, and it ran best with the #142 main and otherwise stock carb.

[Ddw350]

airmancam describes it best,the sound its making.its not really that big of deal...it runs very well,i just thought i could"fine tune"a little.also,when i ran the140 jet,it did blow a good bit of black smoke[more than it everhas] compared to the 138.i tried a 146 on time my neighbor had,it ran terrible,we did it just to see what happened.also hemichallenger,i think honda should get some type of award for easist jet changing ever!thanks for you replies...

[AirManCam]

Im just glad I could help you out man ;)

[J.D.]

airmancam describes it best,the sound its making.its not really that big of deal...it runs very well,i just thought i could"fine tune"a little.also,when i ran the140 jet,it did blow a good bit of black smoke[more than it everhas] compared to the 138.i tried a 146 on time my neighbor had,it ran terrible,we did it just to see what happened.also hemichallenger,i think honda should get some type of award for easist jet changing ever!thanks for you replies...

Actually, it's just as easy to change the jet on that as a Tri-Z, same procedure! :!:

[NICKG]

put in the 140 main jet, then raise the clip on the needle 1 spot and see if it runs better. I suspect that you are seeing the black smoke while reving it up at idle, problem is that you have no load on the motor just zinging it. i had the same problem with my klx650, i upped the main to richen the mix up (if it was rich, you will feel it flatten, lean it would surge) at wot. Remember that the main jet starts to come in about 3/4 throttle. you can effect leaning it out slightly(making a good midrange) by raising the clip 1 spot at a tim till it does not run as good. worked great on my klx. btw Sudco is by far the cheapest place to get jets, less than 3 in most cases. you also make it easier to start by bumping the pilot jet up 1 size too and then adjusting the air screw to lean the idle a bit.

[Ddw350]

i have the 138 in now,i set the airscrew to factory specs,and tooled with the airscrew 1/2 turn at a time,its definately not as bad as it was,but when it warms up a little i will try this...thanks..when i use the 140 and move the clip,should i reset the airscrew to factory setting,then fine tune?

[NICKG]

i always start at 1 1/2 turns out(that may be factory, usually is) does it ever pop if you gun it under load?(thru the carb)

[Ddw350]

not usually,it rarley does it only if it under a real load at low rpm and you gas it it will pop sputter then go ahead and rev up.its never been a big enough problem to mention though......

[NICKG]

ok, if it pops thru the carb under load, you are lean, try the bigger jet and raise the clip like i said. i bet you will like the results. let me know

[timex69]

hey man
check for cracks and missing gaskets in the intake [the peice between the carb and the cylinder]. Try changing your spark plug aswell.

al

[Ddw350]

hey nickg,im gonna try that hopefully this week.i,ll use the 140 and raise the clip.that will lower the needle correct...how bout the airscrew,reset it to factory setting?should i tape up the 1"holes in the airbox lid or leave them open[theres 3 of them....thanks for the info....