HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
philipstjohn

XR650R backfire/pop

17 posts in this topic

What would make the bike pop/backfire and almost shut off or shut off when you brake, let off the gas and pull the clutch in when slowing down or stopping? Any ideas? Running rich or? :lol:

Share this post


Link to post
Share on other sites
too lean..........

The bike came uncorked, air box, uni, Xr's backfire screen, 162 main, 65S pilot, comp needle second seat, manifold, stock exhaust drilled out. Running in Florida, did this early on, but when I re jetted, it seemed to go away. Went to to a 175 main and 68S pilot, comp needle in 3nd seat. Any ideas?

Share this post


Link to post
Share on other sites
The bike came uncorked, air box, uni, Xr's backfire screen, 162 main, 65S pilot, comp needle second seat, manifold, stock exhaust drilled out. Running in Florida, did this early on, but when I re jetted, it seemed to go away. Went to to a 175 main and 68S pilot, comp needle in 3nd seat. Any ideas?

:lol:

You had the problem originally, rejetted and it went away, and now it's back? What changed?

If it got colder, you need more fuel again. Since you're talking about closed throttle operation look to your pilot circuit- how is the idle when warm?

Share this post


Link to post
Share on other sites
:lol:

You had the problem originally, rejetted and it went away, and now it's back? What changed?

If it got colder, you need more fuel again. Since you're talking about closed throttle operation look to your pilot circuit- how is the idle when warm?

In the high 70's here today. Have not changed anything. It slightly popped yesterday, sounded like it was going to shut off but did not. It seems the bike is running richer now, do to the slight black soot in the exhaust I did not have before. And, the bike seems to be running great. Do you think I might be a little low with the idle screw?

Share this post


Link to post
Share on other sites

You can be rich in the main and lean on the pilot, but honestly I still don't understand what the problem is. You have an intermittant condition where it threatens to stall, accompanied with popping?

When you say it's running great now, does this include the near-stalling issue?

Unless there are big changes in air temp then I think you should start by cleaning your carb...

Share this post


Link to post
Share on other sites
You can be rich in the main and lean on the pilot, but honestly I still don't understand what the problem is. You have an intermittant condition where it threatens to stall, accompanied with popping?

When you say it's running great now, does this include the near-stalling issue?

Unless there are big changes in air temp then I think you should start by cleaning your carb...

After jetting, the bike runs great, starts first kick most times, but every now and then when I am ripping along, then have to come to a quick stop, say WOT 4th gear to a sudden hair pin turn, pull the clutch to down shift and it cuts off for a second before I release the clutch and it "bump starts"? Make sense?

Share this post


Link to post
Share on other sites

You said it came uncorked, is that alien looking egr smog pump thingy removed too (not sure if that's even on all the XR's, or just the Cali ones). On a street bike I had, removing that system made the deceleration popping go away. Not really sure why it would want to cut out though, but just a side suggestion. good luck

Share this post


Link to post
Share on other sites
After jetting, the bike runs great, starts first kick most times, but every now and then when I am ripping along, then have to come to a quick stop, say WOT 4th gear to a sudden hair pin turn, pull the clutch to down shift and it cuts off for a second before I release the clutch and it "bump starts"? Make sense?

Well, yes and no.... I understand your description since it was so clear. Why it's doing that? Hmmm.... Maybe your float level is off and you're getting weird fuel flow on sudden decel. Try the Jetting Forum; Burned forgot more *yesterday* than I'll ever know about carbs.

PS: Vacuum leaks can be found by spraying propane or WD40 or starting fluid around the joints between components in the intake system. Do it while the engine is running (avoid spraying flammable stuff on hot exhaust bits please) and listen for a change in idle speed.

Share this post


Link to post
Share on other sites

I had something similiar and found that my gas line to carb was too long causing a kink. Would not get enough fuel and would cause popping and sputtering intermittently. Had to reconfigure fuel line.

Share this post


Link to post
Share on other sites

I agree with cleaning carb, you have a strange problem most people have problems with going from low r's, such as lugging motor through a corner and then trying to accelerate out of turn. with stock carb I ran with needle clip second notch up, 68p and 190 main.

While you have the tank off check the valves for proper clearance just to be safe.

I have stage 1 air box cover mod, ran 175 with no holes.

Share this post


Link to post
Share on other sites

Mine did the same thing yesterday. On my way home after a quick ride, and the bike ran fine all day except for the usual hard start after a tip. But as I was slowing down to turn into my driveway, the bike started popping more than usual and stalled. I bump started it and pulled on into the garage. But it's never done that.

I'm only a few hundred feet above sea level. I recently re-jetted to 68s and 170, clip in 3rd row. Re-jetting made starting a little easier. It was 65s and 175 when I bought it. HRC exhaust spark arrestor in stock can, uncorked, foam air filter with screen still in airbox.

Share this post


Link to post
Share on other sites
Mine did the same thing yesterday. On my way home after a quick ride, and the bike ran fine all day except for the usual hard start after a tip. But as I was slowing down to turn into my driveway, the bike started popping more than usual and stalled. I bump started it and pulled on into the garage. But it's never done that.

I'm only a few hundred feet above sea level. I recently re-jetted to 68s and 170, clip in 3rd row. Re-jetting made starting a little easier. It was 65s and 175 when I bought it. HRC exhaust spark arrestor in stock can, uncorked, foam air filter with screen still in airbox.

So is this a question or a reply to a old thread??

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0