Back Firing KLR650

Z

zeegy

New member
Hi All,

I have a 2003 KLR650that backfires a lot on downhill deacceleration. This is when I am going downhill and close the throttle and let the bike engine slow me down. It kind of sputters and then every once and a while I get this shotgun blast back-firing.

I had some carb problems a few weeks ago (it was idling very rough and stalled unless the idle speed was about 2-3K RPM - it was backfiring then too) and I took the carb apart and cleaned it all up with carb cleaner and blew out the passages with compressed air. The float, float valve, jets, two diaphrams looked good (no tears or holes) and replaced the o-rings. The low speed idling is quite good now. I drilled the pilot needle screw plug and I am currently playing with that but have not seen any improvement in backfiring yet.

I also recently checked the valve clearances and they are too small byone thou on intake and exhaust valves.

My question is: if the pilot needle screw does not change the backfiring, could the valves being out of spec be a possible cause? If so how much wouldgetting the valve shims changed cost approx?

Thanks,

Zeegy
 
Z

zeegy

New member
imported post

imported post

Yes, it is a stock exhaust.

Thanks for reminding me, asI recently replaced the cylinder exhaust gasket and replaced the exhaust clamps further back. I will be sure to check the nuts and bolts holding these together to see if they are loose.

Thanks,

Zeegy
 
Z

zeegy

New member
imported post

imported post

Back-firing update.

Inspecting the acorn nuts on the exhaust pipe to cylinder head revealed carbon deposits on the outside of the cylinder as the nuts were loose!!

I tightened them up and also turned thepilot needle screw out 1/2 turn (make it richer)and sure enough - no backfiring.

Thanks for the suggestion.

Zeegy
 
Swinada

Swinada

Member
imported post

imported post

I know this is a very old thread but i'm trying to solve the same kind of problem and have an additional question.

The exhaust has ,according to the Clymer manual, a seal ring where the exhaust meets the cylinder. well mine does not. I just changed my exhaust from and aftermarket back to stock and i did not see a seal ring in either of them. How can I get this to seal properly to elimate that possability of back firing?

The other option i think is that the PO did some jetting when he put the aftermarket exhaust on and now that i switched back to a stocker jetting might be out of wack. But i dont really have any experience with jetting.
 
K

kawi_klr

Guest
imported post

imported post

you can use silicon for a good seal... just dont get sloppy with it. as for the jetting if you go back to a stock exhaust you WILL need to lean it out... the klrs run way to rich otherwise and hence you wind up with an oil burning problem... so id go back to the stock jetting and maybe just run the k&n filter... should put you near the proper air fuel mix.
p.s mild exhaust popping on decel is a sign of proper a/f ratio... if it wont lean pop on decel your running way too rich on w.o.t
 
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