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Discussion Starter #1
I have a 98 grizzly that has recently came to my possession from a family member. It died on us while hauling wood one day and found out the primary coul was bad. I swapped it out and ran like a champ at idle, however if I give it even the slightest bit of gas it starts to bog down and backfire violently. It did sit up for 4 months under a tarp before I got around to putting the coil in. I love this rig but it is giving me quite a headache lately and I need help.
 

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Did you clean the carburetor and the air filter? The 600 is very temperament when it comes to having both clean.

Have you check valve clearances?
 

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I did not have the air filter on it at the time as I was only testing it. I will check the carb and valve clearance in the next few days when I'm off work.

The strangest part about all of this to me is how well it idles.
 

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I did not have the air filter on it at the time as I was only testing it. I will check the carb and valve clearance in the next few days when I'm off work.

The strangest part about all of this to me is how well it idles.
Put the air filter back in with the filter box cover installed. It might run better like that.
 

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Pretty sure this is a model with the carb boot that will pop off after a backfire....so I would check that boot as well for damage.
 

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Pretty sure this is a model with the carb boot that will pop off after a backfire....so I would check that boot as well for damage.
X2. A great point I forgot about.

A popped off carburetor adapter or a broken/torn/ripped carburetor adapter boot will give you the issues you are having.
 

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Discussion Starter #7
Ok. I checked the valves and they are all within normal limits. The carb boot is in good condition, filter is on and clean. I am running out of ideas. Could the cdi box be bad? Doesnt it have some control over spark timing?
 

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I tried to take the muffler and header off to eliminate a clogged exhaust issue but it had a constant flow of blue flame out of the exhaust ports. After that Somebody also suggested that I may need a upper end rebuild. I am at a loss here. Starting to think the bike is more trouble than it is worth.😑😑
 

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Welcome from Colorado.
I suggest we get the original problem fixed before you start removing other parts that affect the way the engine runs.
If it idles fine then dies with throttle, you have a mixture problem, like crap in the bowl or jet. At idle the gas flow is good but increase the gas required and it craps out.
Have you installed a new plug during this thread? What does the plug look like now?
You asked about a top end rebuild, if it is not burning oil (you would have said something if it was) then that is probably not your problem.
If it was me, I would have a small squeeze bottle containing gas in one hand as I use the other hand to and throttle. If it starts to die add a little gas from the bottle to keep it running with the increased air flow from adding throttle.
 
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