backfire, intake leak?

4 replies to this topic
  • skoaljunkie

Posted January 20, 2006 - 06:50 PM


I just acquired a 93' XR650L that was really abused, I cleaned the carb well, and got it started on clean fuel, the two piece intake rubber between the carb and the head is pretty hard.
The problem is it runs ok but I have to choke it a little to keep it idleing and it backfires and blows small flames back at low RPM. Before I die, I was wondering if the leak could be the solo cause? How to fix it? (RTV blue?), if the carb is set wrong? or if I should check something else like the emission crap/vacum hoses or the valves. It runs pretty well (in the garage) and less-none backfire when I rev it up. Any help would be great. I just "saved" this bike from the salvage and I think it is gonna kick butt.
Thanks again - TL

  • Motosprtman

Posted January 20, 2006 - 07:53 PM


I would go through the carb completely and ensure that all passages are clear and that the jetting is correct (or replace the jets with new ones- from a kit, such as dynojet, FMF etc or use stock Keihn jets from a dealer or web site), check the needle position to ensure your not too lean nor too rich - start off in the third notch and go from there.

Remove the smog junk and install an IMS or simliar block off kit. Replace the dried intake with a new or good used one (check e-bay for one?) don't use blue goo....

Check the float level and install a fresh plug, check the air filter to ensure it is not pulling crap into the motor. Check all electrical connections and the CDI box and stator with a meter.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • AzMtnThumper

Posted January 20, 2006 - 09:01 PM


Is there an aftermarket exhaust, air filter or engine modifications installed on this bike? I would check with some of these L guys to see what jetting they reccomend (it sounds big time lean). I've heard of guys spraying starting fluid on the intake manifold to see if it's leaking (the rpm's will increase if its leaking, indicating a leak). Welcome to TT.

  • GrayGhost

Posted January 20, 2006 - 09:54 PM


yep, if you have a leak in the intake boot, it will do the describe symtoms, and as the previous post noted, a quick shot of starting fluid on the boot will tell the story. But I would also, check the jet sizes as mentioned above.

  • skoaljunkie

Posted January 20, 2006 - 10:13 PM


Thanks for the info so far, any more ideas & tips are welcomed! The bike is stock, I might need to replace the jets as they may have corroded a bit (especially the screw that comes up from the bottom in the front that i think is the air screw {Please correct me if im wrong i am guessing}). If im not planning on upgrading the exhaust or the airfilter I should probably stick w/ factory jets right? Is the "intake rubber" or the carb insulater supposed to be in 2 pieces that just slide together? enough for now, thanks again - TL

Related Content


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.