backfire on f650

**JLawton** · #1 22 Sep 2005

Hello, my F650 funduro backfires when rolling off the throtle, but only when your giving it some gusto. The exhaust is standard and I have just had the original carbs balanced ( which were fine )and the nuts tightened on the exhaust. The guy in the garage said the gas emissions analyzing machine???? showed everything to be fine which would indicate no problems with shims. I have'nt checked shim clearance yet as its a job i want to try and avoid but can not think of anything else. Any ideas???

**ozhanu** · #2 22 Sep 2005

just an idea, be sure both of your sparks work well. Also avoid using chooke.

good luck

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ride safely
ozhan u.
'97 F650
www.ozhanu.com/gezi

**JLawton** · #3 23 Sep 2005

thanks. both spark plugs were new two weeks ago.

**Nigel Marx** · #4 7 Oct 2005

My Funduro has always very occasionally done this for the 5 years I have owned it. I think it's something that some of them do.
Regards
Nigel in NZ

**JonStobbs** · #5 8 Oct 2005

Recently there was a similar thread about KTM backfiring.Usually the cause is a very small exhaust leak letting air into the system,or the tickover being set a little too low.If the tickover speed when hot,is under 1500rpm,increase it to this speed and see if that makes any difference.My XL600 does it just before it needs to be switched onto reserve,meaning it's starting to run a bit lean.Handy really as i don't get that "oh faaarrrkkkk,not now"moment as i try to overtake something and it splutters on the last drip of petrol before i can reach the tap!

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Just going for a short ride on my bike....

**JLawton** · #6 9 Oct 2005

thanks chaps.

i've checked and tightened all the exhaust bolts and do not believe there to be an air leak. I had increased the tickover idle a bit and that did seem to help. I might give it another half turn.

spank you smelly crutch

**Smellybiker** · #7 24 Oct 2005

Hi,

I had backfire problems on my F650GSGD, the problem turned out to be a split in the intake pipe between the throttle stub & the cylinder.

Opening the throttle caused the split to open, air leaked in screwing up the mixture, and BOOM.

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Last seen in S.America, missing presumed fed.
http://www.smellybiker.com