Just picked up a 1994 Polaris 400L 4X4. Rebuilt the pull start and replaced the starter drive while I had the side open. Rebuilt the carb, sealed some air box cracks with epoxy, and replaced the airbox rubber boot to the carb. I can now plug the intake and the engine dies where as before it would suck air. The bike starts fine now both electric and pull starting and Ive got it idling after it warms up. My issue is, it seems like there is some top end speed missing. The speedo doesnt work so not sure how fast it goes at this point. The guy I bought it from said it should go 60-65 MPH. Any suggestions? I've run across a few different posts about reeds. I have never messed with them before and could this be a factor?

 

Its a 50-53 mph ATV. My 500 H.O run great and just gets over 55-57 mph on flat hard pack.

My friends 660 Yamaha Grizzly does only 60-63mph. Not a lot faster but he bleeds less speed off when a long incline shows up as well.

These are speed from and pickup truck following us on a wide flat long gravel road since ATV speedos are optimistic.

 

If your gear case doesn't have the carb dampener on the gear case,could be part of the reason if it's not running top speed. Tech bulletin came out on all 94 400 models to add this to help stop the carb from vibrating and dumping fuel into the reed cage.Not all owners had this bulletin done. 95 and up models have this dampener.Rarely would reed pedals warp/split or break off,but you can check em.If it idles good,I wouldn't think they were the problem. Brand new out of the crate with stock tires the 400 2x4 would hit right at 65 on a straight road we had by the side of the shop. 4x4 was a tad slower because of the extra weight,BUT AGAIN these were brand new.Plus don't overlook a worn belt, clutch buttons and also the simple fact its 20 years old.I don't run as good as I did 20 years ago to say the least either.. Dampener on this 95 model is #8 on the parts breakdown.
Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

I'm not too sure I ran too good 20 years ago.

 

Kinda figured you or someone else would hit that one.Knew I left myself wide open when I posted

 

The dampener is already in place so i may replace the belt to see if that does anything additional. Thanks for the help!

 

Forgot to mention that these old early speedos weren't that accurate on the 400s. We found that on the first 350s that we got in also. You could peg the 60 mph speedo with the light 2x4 and running along side a street bike that would show around 4mph faster. Never liked the transmission adapters,then the "key" that that turned it,then the cable from it to the speedo.Item 17,22,and 24 on the parts breakdown.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse When the 500 came out,the 400 would just walk away from it from a dead stop.Loved em until I had to completely rebuild the first one. A whole lot to these engines.

 

I threw a new plug in it tonight and found what appears to be a broken motor mount right on top of the frame under the gas tank. There is a piece of maybe 6 gauge wire bent to both sides of the mount. I'm assuming this is not normal. Any insight?

 

Normal. That's the engine to frame ground wire. Item #5. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

There is a lot of vibration at that point. I'm assuming the bolt that goes through the rubber bushing is supposed to be solid.