86 200x backfire

[philgipson]

i have a 86 200x that i just did the top end on.runs like a bat outa hell but pops during deceleration.has cobra exhaust.am i too lean or too fat?

[Liquid-Darkness]

Lol I know im too fat hehehe, probably too lean on the main jet. Whats your bikes jetting now?, whats the stock jetting and what mods does the engine have??

If jetting does not fix it, then maybe your valves are too tight??


My 350X has a K&N air filter and a Cobra exhaust and I am jetted up a bit but it still pops a little when deaccelerating. Its not as bad as it was when I first got the bike, but it needs to be a bit richer on the main.

[philgipson]

i dont remember the size but the main is correct stock,ill check it.and yes i am fat.no mods to the motor,it measured out and went back stock.thanks

[atc007]

Most likely lean,but check your intake for any air leaks with starting fluid.

[barnett468]

Hello philgipson;


Actually, you never jet a bike for deceleration. Decel popping is not always related to a lean condition or single source. In your case you most likely need to go up one on the main.

I have never removed a stock ex and installed a hipo ex without having to increase the fuel amount. This has typically been an increase in the pilot by one size and the main. I also occasionally raised the needle one position. This was below 1000 ft elevation.

Even though your bike seems to run ok, I would do a plug reading and try a 1 size bigger main and probably raise the needle one position for starters. Slightly rich jetting is better than slightly lean jetting.


You should jet it properly, mainly for the following:

Starting
Idle
acceleration from a dead stop
acceleration from a steady speed


Once properly jetted it is going to do whatever it is going to do on decel.

I seriously doubt that even my good friend Mickey Dunlap cared what the heck his bike did on decal.

None of our Kawi Super Bikes or MX bikes were jetted for decal and they seemed to run just fine.

Jay Springers National Championship Harley half miler popped like the dickens on decel while shooting flames out the pipe but it seemed to run just fine.


If for whatever reason you want to try and reduce or eliminate a decal pop then some of the things you can try are:

Lower the slide

Raise the slide

Lower the needle

Raise the needle

Turn the fuel mix screw in around 1/2 turn.

Turn the fuel mix screw out 1/2 turn.

Increase the pilot jet size.

Decrease the pilot jet size.

Increase the choke height of the needle jet.

Decrease the choke height of the needle jet

Check exhaust valve for a leak.

:beer

[barnett468]

Sorry, post addition.

"These are in addition to liquid darkness and atc007's suggestions."


I'm the only only without an edit button.

http://www.freesmileys.org/smileys/smiley-laughing025.gif (http://www.freesmileys.org/smileys.php)

[Liquid-Darkness]

Yep everything barnett468 (http://www.3wheelerworld.com/member.php/34281-barnett468)

said is right. Up a main jet a few might clear it up. Also checking for an intake leak on the intake boot. Good luck dude!!

192573

[RIDE-RED 250r]

Kind of goes along with what has been suggested, but I have also found going a size or 2 richer on the pilot jet helps alot with severe backfiring on decel with a thumper with exhaust and K&N... As suggested a size or 2 richer on the main will most likely be in order.

Think about it, when you are accelerating you are running off the main jet circuit regulated by the slide needle up to about 3/4 and then beyond that you are pulling from the main circuit unrestricted by the needle. But when you let off (decelerating) you close off the main jet circuit completely and are now pulling from the idle circuit. The pilot jet greatly effects the idle circuit. If it is too lean on the pilot circuit it will backfire like a son of a gun on decel.... I have had personal experience with this exact issue several times with 4-strokes with pipes and filters, and on all counts a richer pilot along with main was the cure. The main jet change improved performance up through midrange to top end, but severe backfiring on decel still persisted. Richer pilot jet took care of that. I have experienced this with 350x's, 250sx's and 200x's

I think a common mistake people make is to throw on an exhaust and better filter and only bumping up the main 1 size, if they do anything at all.