Jump to content
Sign in to follow this  

Quick ???

Recommended Posts

05 crf 450r, can a valve that is not sealing properly cause the bike to back fire and shoot flames out of the exhaust???:)

Share this post


Link to post
Share on other sites

Have you check valve clearances lately?

Share this post


Link to post
Share on other sites
Have you check valve clearances lately?

Yes, valve clearances are all in spec. I'm just having trouble with the bike popping when you give it a little throttle, I mean it pops loud and shoots flames out the tail pipe.

I was wondering if 1 or more of the valves weren't sealing right when it closes, could that make this happen??

I know the valves are not be held open by too little valve clearance, the intakes are at .005 and the exhaust are .012.

I've tore the carb apart several times and cleaned and blew it out, still popping.

I've changed the coil out, plug wire end, swapped the cam timing by 1 tooth forwards and backwards of normal timing, replaced the copper head pipe gasket, ran it with out the silencer and mid pipe, changed out the entire wiring harness with a different 1 from the same year bike.

I'm running out of ideas, and nothing seems to help.

One other thing I was thinking about was if the decompression piece on the end of the cam was malfunctioning and releasing compression, could that make it pop??????:banghead::p:foul::busted::banghead::)

Share this post


Link to post
Share on other sites
have you checked for an exhaust leak near the head?

Yes, Ialso replaced the copper gasket at the head pipe and it is still popping.

Share this post


Link to post
Share on other sites

Mid pipe clamp is tight? No leaks anywhere else in the pipe? May be dumb, but have you tried a richer pilot jet? If adjusting carb settings is doing nothing, if you have the access, swap out the carb for a buddy's (That works well) and see if the problem still exists, if so, you know its not the carb. If you haven't tried losing the pop by backing out the Fuel screw or giving it a richer pilot search for a place where extra air is getting into the engine...

Share this post


Link to post
Share on other sites
Mid pipe clamp is tight? No leaks anywhere else in the pipe? May be dumb, but have you tried a richer pilot jet? If adjusting carb settings is doing nothing, if you have the access, swap out the carb for a buddy's (That works well) and see if the problem still exists, if so, you know its not the carb. If you haven't tried losing the pop by backing out the Fuel screw or giving it a richer pilot search for a place where extra air is getting into the engine...

Yes, I've went richer on the pilot, needle and main, no difference. I also tried running it with the mid pipe and silencer off the bike (LOUD AS CRAP) but still popping.

I also tore the top end off it and replaced the gaskets, head and base, still popping. I looked on ebay today thinking about buying a different carb to try but the cheapest one was $250, don't want to spend that much on a experiment.

Thanks for all the ideas today guys, please keep them coming..

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  

×