My good friend has a 660 Grizzly....it's a beast....a couple of questions.
1. He put a bigfoot package on it...big rims and BIG mud tires (not sure what size)
2. He punched out the baffles in the silencer
What does he need to do to restore the top end and get it running right?
I'm thinking something with the clutch and maybe re-jet the carb.
We're both pretty new to this so any help would be appreciated.
Thank you all in advance -Joe

 

You didn't realy say what's wrong with it. How is it running? The bigger tire you put on the more power it's going to rob. If he opened up the pipe, he may be running lean. If this is the case he definately needs to rejet it before he burns it up.
Try and give as much info as possible and you will get a better answer.

 

Putting on the big wheels and tires, does kind of kill top end, its a double hit...the final ratio changes , and the tires are usually much heavier. Try pulling on the choke, when he feels like it needs more, this will slightly enrichen the mixture, and if this helps, then have him go one up on the main jet. I think two up would be too much, considering all hes done is punch out the baffle.
The clutch kit, will improve low end response, but I dont think it helps the higher end.
Heres an article on rejetting, and it has drivability symptoms and solutions, this may help diagnose the problem, if its carb related.
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lets start with elevation. what is your riding elevation at? if its sea level, then i would be surprised if he's running lean just drilling out the baffle. he DID put in a larger end cap, right? take off the 3/4 in. tip, and install a 1 1/2 inch tip. he isn't running with no end cap, is he?
we need more info to help out with.
elevation.
any aftermarket parts like a k&n?
size of tires.
any carb mods?


the griz runs rich from the factory, so you do have a little play with it. answer the questions, you'l get answers.

 

What he did is stick something into the pipe and start rootin around at the baffeling. I didn't see the process, all I know is the thing is MUCH louder and seems to be "sick" more often then it did. He needs to add fuel additative to it once in a while, that seems to help, but it is losing top end speed. It is now running about 57mph flat out. We are pretty close to sea level (west-central Illinois). It will run good for about three rides after he adds the additative, then it won't start right, loses power drastically, loses speed, etc....
We're not easy on these machines, but I run a Scrambler 400 that never has these problems. I would say that out of 10 rides, the Grizz needs work 3-4 times if they are just easy putting around rides, and more often if we beat on them in the mud. It also wants to overheat. We were riding in the woods the other day on sloww technical rides and the thing kept on overheating. It was 30 degrees out. Coolant level is fine, fan works. Like I said neither of us are atv mechanics or anything, we're just lookin to have some fun.

Tires are mud tires that look like something that should be on a tractor, I believe the rims are ITP aluminum, he calls it the "bigfoot" package
The silencer looks stock, but sounds like a header
No carb mods
We are close to sea level (west-central Illinois)