Intake backfire

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L

ld

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My warriors backfiring through the intake(hot or cold). Its a light backfire more of a puff. sometimes theres a click sound - im kinda thinking its the carb slide closing fast?? Usually it will die when this happens. Some times it will do it a few times before it dies. When the chokes on or its reved up it will stay running - it still backfires throught the intake just not as much.

Ive cleaned out the carb twice.
Ive checked the timing.
Ive checked the valve gap.
Ive replaced the intake boot.

As far as I know everything internal is stock. Its got a DMC full exhaust. Proflow K&N filter Stock air box. 150 main jet.

It was running fine. Next time I rode it it backfired but stayed running. But sometimes randomly stalled. The next time I rode it backfires and dies.

Reason for replacing the intakeboot:
I was thinking vacuum leak. I turned the idle up so it would stay running. Still backfired a bit but stayed running. I sprayed brakecleaner on the intake boot area. When spraying on the clutch side it appeared the engine would rev up. I read in a few places the intake boot was common for cracking so I replaced it. Didnt fix the problem.

Unless im crazy it seems that when I spray the back corner of the head gasket(clutch side) with brakecleaner the engine revs up.

The ground strap on the plug is white indicating lean. When I changed it last the old plug looked like it might have been a bit rich.

Anythoughts on where to look for my problem?
Any opinions on the headgasket + brakeclean = engine rev?
 
compression test ? and you shouldn't brake cleaner. it can eat rubber

i'd say you have an air leak somewhere
 
I thought about a compression test but ill have to hunt down the correct hose to fit the head. other wise id have already done it. Thanks for the input.
 
My bike does the same thing. I noticed on the other side of my head something like that. it looks like its leaking oil so maybe thats what it is.
 
Have you tried to retorque the head bolts? Can't hurt. They don't take very much torque, probably because the bolts are so long and thin to begin with.
 
I got a compression tester hose that will fit so im gonna try and check that tonite. Theres no oil leak from the head gasket area. The cylinder base gasket is staring to get some oil seepage on the other side.
I guess I could try and retorque the head bolts. I didnt think that was the best thing for headgaskets. But its worth a try.

Thanks for the input.
 
As long as the gasket(s) aren't blown out, then yes it's ok. Bolts strech, and can back out from heat cycles. Overtorquing is worse than undertorque...don't overdo it.

I'd consider checking for a possible burned or sticking intake valve. Might show itself on the compression check.

Also, you can't read rich/lean off of the ground strap. Read it off of the porcelain:
http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp
 
well i think thats were mine is then its were the top end connects to the lower end on the left side of the engine.
 
My warrior was doing the same thing before I rebuilt the whole topend, still doing it. Someone said if the pulse coil is shot it will cause similar symptoms
 
From what I've found. If the engine is lean at 0-1/4 throttle settings it will back fire through the carb. You will hear the air blow the slide back because the change of pressure difference. So that is why you hear a clicking sound.

Anyway, I would make sure the carb is adjusted to factory settings first on the fuel screw. I believe it is 2 turns out. If you are running more open filter and exhaust you will have to back this screw out. To set this screw perfect. You just idle the engine up to about 1800-2000 rpm. Turn until you get maxium rpm and smoothness out the engine. Sometimes I find after doing this I may have to adjust it a 1/4-1/2 back out so the engine will not backfire when slowing down off the throttle.

Other things it could be if this isn't the problem are.. to tight on valve adjustment and cam timing.
 
Mine does this when its cold and warming up it kinda like coughs back into the intake but still runs.
 
dirtrider73068 said:
Would that be pilot or main or both?
Click to expand...


Main is only 3/4 and up on the throttle.
Needle is 1/4-3/4 throttle.
Pilot, air jet and fuel screw control 1/4 and under.

So I would adjust the fuel screw out, but if it is backed out more then 3 1/2 turns then you have to go bigger on the pilot or smaller on the air jet.
 
Yea the fuel has to be turned out to almost falling out, so about 4 turns before it quits or runs decent. I thought it might be way too lean on the pilot.
 
I just fooled with mine, again, for the 6th time. Honed the 42.5 out with a wire from a cup wheel (wire brush) and removed/cleaned the tip of the adjustment screw. Fires up much easier now.

I have a #45 jet -on backorder- (???) from my local Yamaha dealer. I'll probably just cancel it and order it online.
 
dirtrider73068 said:
Yea the fuel has to be turned out to almost falling out, so about 4 turns before it quits or runs decent. I thought it might be way too lean on the pilot.
Click to expand...


If it is all stock or close to then I would recomend cleaning the carb.. If not then you know you have to go up on the pilot jet one size.
 
Just an update on mine. After swapping/buying several parts I picked up a used carb for a good price. I swapped the main jet to the bigger one out of my carb. Cranked it up and it runs fine. It seems theres an issue in my carb somewhere. Either somethings worn out or its got a clog in it somewhere. Anyways just some info to maybe help out someone else in the future.
 
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