Jump to content
Sign in to follow this  

backfiring on acceleration Rich or lean?

Recommended Posts

My 06 rmz450 pops or backfires when I get on the gas after letting off the throttle. It does it most after hitting a jump face then nailing the gas when landing. It doesn't do it if the bike is being bogged, only when riding hard.

I have check the following;

Exhaust for cracks or leaks

Valve clearance and timing

Installed new sparkplug

Cleaned carb checked all jets

made sure air filter didn't have to much oil.

Also the bike doesn't idle real smooth. This pretty much started to happen after I replaced the piston. Any ideas is it running rich or lean I cannot tell from the plug

Share this post


Link to post
Share on other sites

backfiring is 97% of the time a lean condition on an mx bike it can be a rich condition but usually a mxer will not run if u are expeiriencing a backfire due to a rich mixture what type of piston did u put in the bike?? oem-- aftrmkt high comp?

Share this post


Link to post
Share on other sites

How about air leaks in the the intake boot, between the carb and head? A small crack or an area not properly clamped / sealed will give this symptom most every time. With the perimeter frame that area is a real*@#$%^+ to get to.

Share this post


Link to post
Share on other sites

I had a similar problem with mine a couple weeks ago. I would check your pilot and slow jet circuit. Also check the seal between your carb slide and slide plate. Do a very, very thorough job when you clean out your carb. I had mine apart 7 times till finally whatever it was in there came out.

Share this post


Link to post
Share on other sites

Mine did the same thing, I had to replace the stator. Runs great again. All symptoms point to jetting but it was ignition.

Share this post


Link to post
Share on other sites

Hey ! Check your low speed mixture screw .. Mine fell out(Vibrated). I was truly baffled by the problem because I couldn't figure it out for days . After all it was the first ride on my new bike (Used) =(....

If it is gone just get on that you can adjust(thumb style ) and make sure to get the new spring and the o-ring to go with it .

Share this post


Link to post
Share on other sites

Just found the problem, I haven't had time to work on it lately. I was going to replace the pilot jet and while pulling off the carb I noticed a little play in the intake boot. Sure enough it was cracked. Funny that's one of the first things I checked, seemed tight at the time. Oh well thanks for all the suggestions

Share this post


Link to post
Share on other sites

It would also do this if the fuel screw is starting to come out which they do sometimes when you throw an aftermarket one in.

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

Reply with:

Sign in to follow this  

×