I have a 2001 220 Bayou that starts perfect and idles great, it has a noticeable ticking in the top end of motor that I assume is a valve adjustment? It runs perfect at low speeds in every gear and has ok power , until you open the throttle half way or more then it bogs out and loses all power, this happens in neutral as well, My question is the reverse ****/switch is sticky and it will shift into reverse without turning the ****,,so I dont know if there is a reverse rpm limiter /decompression that could be stuck? Or could it be the valve adjustment making it lose power in the mid/upper range of the rpms? I have cleaned/rebuilt the carb, cleaned the air filter, new battery etc. It really stinks cause its in excellent cosmetic condition. I appreciate any/all help anyone could give, Thanks , Ron

 

I would adjust the values any ways. Is a easy job just find out your clearance numbers for you exhaust and intake. Here is a vid on it. Its a Yamaha but there done more or less the same. Unless your atv is the shim type but youtube has vids on that also.

 

things to consider
Air filter/intake in good shape, not plugged with debris or mouse nest
Fuel fresh/good
Fuel line not kinked
Fuel line, if has filter, make sure filter is clean
Fuel petcocks sometimes have little filters so make sure those are clean, have to take petcock off tank to verify

Spark plug good? Not that it could cause those symtoms
Spark plug cap/wire

Carb - I know you said you cleaned it, but I think if all of the above are ok, then I'm thinking main jet or needle may need cleaned/adjusted. Maybe needle isn't installed right. Maybe 16017a/b part isn't installed right. Easy to put this in from carb throat when I believe it goes in from bottom? If the atv ran fine, and wasn't run for a few months, then all of a sudden acted up, I'd suspect carb.

Valves - I would suspect if the valves were the culprit, the problem would have progressed over time, getting worse and worse, unless one of the locknuts came loose and let the screw adjuster get out of adjustment real quick.