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Discussion Starter · #1 ·
It back fires and blows the boot from the head to the carb off. I have done a tune up and still does it.

It does it while cold starting. After warming up it is good to go.

Could this be the CDI, coil or what. Anyone have an idea?

Thanks

Chief
 

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Check valve clearances. More than likely tight.

Check Pulse Coil resistance as well. Could be just outside limits when cold, but within limits when hot. Either way, if it measures outside limits at any point, it needs replacement.

If the valves and pulse coil check out good and you still got the issue, remove flywheel and check for sheared woodruff key.
 

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Have you adjusted the valves?
With improper valve lash, the valves do not fully close allowing back pressure to the carb.
Grizzly valves are known to stretch slightly over the first few hundred miles closing the lash gap and many find the valves need adjusting. On most machines, this is done once then not needed again.
 

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2001 Grizzly I was given had sat, unused, for at least three years. The gasoline I drained from the tank was GREEN. Stuff in carburetor was like a Gummi Bear. I cleaned out the carb, reassembled/installed it and while the engine RAN, it popped, backfired front AND rear then died. Pushed it into the garage, got a parts kit, cleaned it again, reassembled/installed, started first push of the button. Runs great now - knock wood.


You MIGHT save yourself some time/effort/trouble and check the carb FIRST; clear jets/etc.
 

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For those asking questions about their machine, adding a signature listing the mods and miles helps other help you.
Signatures appears in all posts.
In this thread, the miles are not known and as once warm the grizz is good to go, I figured there was less chance of a fuel restriction, and a higher probability of valve lash on the low end of the recommended range, so as the temp comes up the intake valves seal more firmly.
The deal is, to get to the valves, the carb is right there so pulling the carb to remove the bowl for a look-see is no big deal.
I don't like messing with the carb unless needed because of the throttle and choke connections on the 660, and the fact the bowl screws can be easily rounded. When I did experiment with changing jets, I replaced the Phillips screws with Allen head drive bolts for ease of removal the next time.
 
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For those asking questions about their machine, adding a signature listing the mods and miles helps other help you.
Signatures appears in all posts.
In this thread, the miles are not known and as once warm the grizz is good to go, I figured there was less chance of a fuel restriction, and a higher probability of valve lash on the low end of the recommended range, so as the temp comes up the intake valves seal more firmly.
The deal is, to get to the valves, the carb is right there so pulling the carb to remove the bowl for a look-see is no big deal.
I don't like messing with the carb unless needed because of the throttle and choke connections on the 660, and the fact the bowl screws can be easily rounded. When I did experiment with changing jets, I replaced the Phillips screws with Allen head drive bolts for ease of removal the next time.



If it's ONLY when cold, and choke's applied, there's a greater chance it's fuel-related, NOT electric.


That part of the carb can be accessed easily w/ the carb on the machine (is on the 600 anyway), some carb cleaner spray and/or some gumout or seafoam added to a tank of fuel might clear out any obstruction/restriction.
 
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X-2 on not likely electric related as it has spark to run and warm up for a ride.
 

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Discussion Starter · #8 ·
It was back firing when I bought it two years ago. I have replaced the carb, but it was a bad float so I just replaced the whole thing.
I will adjust the valves and get back with y'all. Thanks for all the help.
BTW it is a 2000 Grizzly 600, miles UNK due to a broken spedo cable.
No MODs other then 27" tires. Old man deer lease quad.
 
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