Backfire after Bimmer Bits Install

[carpbiker]

New guy here.

 

I recently replaced my cracked Throttle cams with the Aluminum BB parts. The installation was fairly straight forward. After Installation I performed the throttle relearn procedure and the bike fired up with no issues.

 

However, after running for only a few miles I am experiencing a backfire at idle but nowhere else in the rpm range. If I rev the engine it will backfire as revs drop. Bike runs fine except that. 

 

Usually I figure a backfire is due to lean condition so I sprayed carb cleaner around the TB area with no change in the rpm. I also replaced the injector o-rings to be sure. Nothing else was removed when I put the new cams on.

 

My question is, has anyone seen this before and have a cure? what else should I be looking at? I do not have a GS-911, but have a multi meter.

 

Thanks in advance.

[dirtrider]

23 minutes ago, carpbiker said:

New guy here.

 

I recently replaced my cracked Throttle cams with the Aluminum BB parts. The installation was fairly straight forward. After Installation I performed the throttle relearn procedure and the bike fired up with no issues.

 

However, after running for only a few miles I am experiencing a backfire at idle but nowhere else in the rpm range. If I rev the engine it will backfire as revs drop. Bike runs fine except that. 

 

Usually I figure a backfire is due to lean condition so I sprayed carb cleaner around the TB area with no change in the rpm. I also replaced the injector o-rings to be sure. Nothing else was removed when I put the new cams on.

 

My question is, has anyone seen this before and have a cure? what else should I be looking at? I do not have a GS-911, but have a multi meter.

 

Thanks in advance.

Afternoon  carpbiker

 

Did you do ANYTHING else to that motorcycle while it was apart for cam replacement?

 

[carpbiker]

Nothing else was done, other than removing head guards. 

[dirtrider]

7 minutes ago, carpbiker said:

Nothing else was done, other than removing head guards. 

Afternoon carpbiker

 

I presume by backfire you are talking about a post fire out of the exhaust rather that a backfire pop back into intake?

 

If you have no air leaks into the intakes between the throttle plate & the intake valves then next place to look is to be darn sure both side throttle levers are FULLY returning to the idle stop screws.  (it's easy to pull a throttle cable out of the splitter box or not fully seat a cable into the TB adjuster fitting. 

 

Added: are the throttle return springs clearing the new wider cams & not hanging the throttle up on closing? 

 

 

[carpbiker]

Good call, neither are seating against the stop screw, now to determine why. Thanks 

[dirtrider]

14 hours ago, carpbiker said:

Good call, neither are seating against the stop screw, now to determine why. Thanks 

Afternoon  carpbiker

 

You either have the cables pulled out of splitter box or they are just too tight due to the new (non OEM) cams. 

 

Up by the twist grip is a main cable adjuster under a rubber boot, you m-i-g-h-t be able to adjust that enough to get the throttle to return to the stop screws without having to mess with your above-idle cross side balance. 

 

But first make sure the short cables are fully seated in the splitter box & fully seated down in the TB adjusters.

[carpbiker]

Just to follow up, left cable not fully seated into the Tb, cables too tight preventing the fully seating against the stop screws. both fixed and runs fine. Thanks for the help.

[dirtrider]

10 minutes ago, carpbiker said:

Just to follow up, left cable not fully seated into the Tb, cables too tight preventing the fully seating against the stop screws. both fixed and runs fine. Thanks for the help.

Morning  carpbiker

 

Thanks for the update, we always like happy endings___

[aggieengineer]

If Dirtrider ever quits this hobby, we are just so screwed.

Great thread, great outcome.