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ATV backfiring issues

72k5mike

72k5mike

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I figured I would ask here. I have a 99 yamaha wolverine, it sat for the past 4 or so years because of an oil seal leak. the leak has since been fixed, and the carb cleaned out. The engine starts good, idles good, and accelerates good. when the engine is decelerating (no load, just revving the engine - I have not put a load on the engine yet) the engine backfires violently and occasionally blows the carb off.

Im reading quad forums and they say that it could be an intake issue or a lean carb issue. I have checked for intake leaks and have come up with nothing.

Any other ideas??
 
How do the plugs look? Fouled plugs? Intake leak? Carb could still have some crap in it.
 
It's definitely a sign of a lean issue.

Did you remove the slow and main jets, and main jet cross bleed tube and ensure they were clean and free of obstructions when you cleaned the carb?

What about cleaning all the ports and passages in the carb body?

Did you remove the float needle and seat and clean them, as well as, set the float height?

It sounds like varnish has plugged something up and is causing fuel to not flow correctly.
 
wasted wages said:
adjust the valves..... Yamaha's are notorious for closing up the valve clearances and causing them to go lean and backfire....

My 02 660 grizzly drove me crazy till i read up on it...

here's the first of a three part video on how to do the valves..

http://www.youtube.com/watch?v=lXYjNLzrkeU
Click to expand...

Do this ^^ older warriors were famous for the same problem as you are having and since it is the same basic engine .......
 
I can't remember, is the wolverine a 4 valve motor or 2 valve warrior motor? Either way, like been said, make sure the carb is clean. There have been MANY times a friend says his carb is clean but after I get a hold of it, then it's clean.

Also, my '03 warrior has gone through some problems with the carb because it sits too. If you have a white plastic cover on the outside of your carb, on the side of the carb....held with two or three philips screws, there is a diaphragm with plunger inside. Not sure if the older wolverines had this type of carb or not. This plunger likes to stick inside the bore. The whole setup is goofy, but the plunger/diaphragm moves with throttle changes. Clean the bore and plunger really well and spray with WD40 or something a little thicker, maybe even a little lightweight oil.
 
also, to see if the engine is running lean or rich:

duct tape almost the entire intake box hole, if it runs better, it's running lean
pull the airbox lid off and run it, if it runs better, it's running rich

if neither help, it's a problem with you carb's circuits or spark. I have seen my share of freak electrical components though.
 
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