PDA

View Full Version : Backfire?


jjthekj
06-08-2004, 08:45 AM
A friend asked if I could help him troubleshoot/repair his quad. He said his quad "popped" and wouldn't start again. When I got there I saw that the carb boot (intake) was dislodged (no longer sealed). So I put on some new clamps sealed it back up, and it ran fine.
He called me back and told me it's happened again.
The best I can figure is it's backfiring.
I'm looking for the cause of the backfire and the solution to keep it from happening in the future.
Spark plug? Timing? Jetting?
BTW. The quad in question is a '99 600 Grizzly. (I know it's not an EX, but, most here have experience beyond Honda).
Any help would be much appreciated!
06-08-2004, 08:48 AM
has he made any changes to the motor/intake or exhaust????
jjthekj
06-08-2004, 08:50 AM
It's stock.
cals400ex
06-08-2004, 11:23 AM
my buddies 99 did that bad too. his header and silencer cracked.
hondarider2006
06-09-2004, 12:07 AM
My buddy has an '03 and it backfires hella loud all the time on decel, and right after you shut it off. Them things are nothing but a pain.....
jjthekj
06-09-2004, 02:01 AM
OK. We've established that it is a problem that exists. I'm sure someone has overcome this problem in the past. It's not just that it's backfiring, it's blowing the carb off the intake! It's really no big deal, reclamping the carb boot, but, I know it's gonna happen again!
jjthekj
06-14-2004, 10:57 PM
:confused:
cals400ex
06-15-2004, 03:31 AM
nothing a little duct tape shouldn't fix
deansfastway
06-16-2004, 10:43 AM
Maybe the valves are out of adjLoosen the valve adjustment and richen it up a little bit .
400ex28
06-16-2004, 11:22 AM
Originally posted by cals400ex
nothing a little duct tape shouldn't fix

Now there ya go! :p
jjthekj
06-18-2004, 11:41 AM
When I went to look at it I brought my duct tape, a big screwdriver, and all my best hammers!
Sure enough, it popped off a second time. When I put it back together I could see the carb attempting to pop back off as the engine idled. It was visibly jumping back and forth with each "off beat" backfire (ish) pulse of the engine.
It's my best guess that the valves are due to be adjusted.
cals400ex
06-18-2004, 01:51 PM
Originally posted by jjthekj
When I went to look at it I brought my duct tape, a big screwdriver, and all my best hammers!
Sure enough, it popped off a second time. When I put it back together I could see the carb attempting to pop back off as the engine idled. It was visibly jumping back and forth with each "off beat" backfire (ish) pulse of the engine.
It's my best guess that the valves are due to be adjusted.


i was kidding about the duct tape, but whatever works. i would make sure the jetting isn't lean and causing it to backfire. yeah, give the bike a full tune up and see if that does anything.
Aallron
06-18-2004, 06:26 PM
When it does run, does it run ok or does it seem restricted on power. I would check for restrictions in the exhaust first, because it doesnt cost anything but time then if it isn't too much work I would check the cam timing... Ill bet the intake cam has jumped a tooth if dual cam.
jjthekj
06-21-2004, 01:16 AM
A friend stopped by today, who is a car/boat mech (he rides a 300EX). He sugggested it may be running lean as well. Causing a "lean backfire". Thinking back to my conversation with the quad's owner he said the quad was a "bear" (unintentional pun) to get warmed up in the winter. I'm starting to target his pilot jet. Clogged? Too small? Hmmm......