Any help would be greatly appreciated:

I have a 01 ds650 recently installed an fmf titanium 4 mid-pipe and muffler along with a K&N filter and jet kit and I followed the instructions to the T. Now it backfires at higher rpms. To the point of not being able to ride all I can do putt around. To make things worse just after installing these parts I took it to Mexico for spring break. The elevation change made the backfiring much worse so I concluded that I was running lean( the elevation here in New Mexico is around 5200 ft )
the stock jett is a 165 I have changed the main jett from stock to 170,175,180,185,190, and now Im running a 200 way to fat for my elevation and limited mods(elevation again 5200 ft). I have also tried every combination of jet and needle setting imaginable. Also I have checked my intake boots for cracks or any kind of air leaks nothing! Needless to say I am getting pretty feed up.

CAN ANYONE HELP ME?

 

That does sound lean.

I don't know what to try, but I'm no expert on jetting. Try posting this in the Bomb forum.

 

what do your plugs look like if you do a plug chop?

 

Dumb question, but when the valves are tight does it backfire at low or high rpm's. I know if your valves haven't been adjusted lately they can backfire.

Justin

 

Hey that would be a good forum...Valve adjustments!!!! Whats the clearance???? Dose the DS have alignments holes for valve adjustment? do it cold, or warm???

 

Mongo, When is it backfiring, while you are on the throttle? or after you let off. If it is backfiring when you let off the throttle then it is usually a sign of a lean pilot circut. How many turns do you have your air screw out? Try turning that in one full turn at a time and see if it helps. If you get it all the way in a it dosnt change then you need to go up one size on the pilot for every full turn of the screw at you did.

 

You could try a larger pilot jet. My Raptor did that after i installed my pipe (backfired at high RPM) untill i changed them out.

 

My Big Gun full exhaust used to backfire at high rmps too. Replaced that pipe with a ti4 fmf coincidentally. Got it to stop though by replacing the header gaskets and tightening the bolts evenly. If cold air gets into that header pipe it will cause it to backfire especially when you are at higher speeds and coasting without throttle. Mind you my jetting was fine and had no backfiring before the header bolts loosened and the gaskets burned away. Now I am back to the stock headers with the Ti4 pipe. No backfiring at all. Used new gaskets and the stock header just fits better anyway.

 

I heard the big gun rev limiter is only 500rpm over stock, Are you sure you arnt hitting it?

 

Thanks for the help so for guys,

Saint 650- my plugs are fine sort of a medium/light brown.

Baja Iowa- I do need to run the valves has'nt been done in a while

Shav0-It is backfiring while on the throttle it almost seems like it does it 1 or 2 thousand before the rev limiter, the air screw is out 2 1/4 turns.

Lomax- that is something I will have to look in to

Big John-That is something I would have never thought of, thanks I will check that.

Annihilater-I havent yet gotten the rev limiter yet it is on nation wide backorder been waiting a month already. But it sure seems like it is doing it fairly early. As far as big guns rev limiter being only 500 over I will have to look into that if it is true big gun can keep there limiter. And thanks alot for posting this again, thank you!