It sounds like if the plug was dry that the engine is actually starving for fuel. Have you pulled the carb and checked the jets for dirt or debris? I know you said you messed with the float but did you go through the entire carb? I had a dirtbike that got dirt into the fuel system one time and I had to throughly clean the carb about 3 times before I got it all cleaned up. It would run good for about a tank of gas then dirt would get in there again and bog. It did the exact same thing you describe. Did this atv sit for awhile to where the jets could have gotten gummed up with bad fuel? I would start there before you go tearing into the engine. How many miles or hours does it have on it? It also could be a bad ignition. The 500HO engine is pretty bulletproof and the cam wearing out would be a gradual increase in power loss. Not an immediate bog like you're describing. To me it sounds like its fuel or ignition related. Brian

 

Briman, I thoroughly cleaned the carb and i know that the jets are clean, and I replaced the needle float & seat.
The wheeler has 1850 miles on it, and it belongs to a farmer. I know he ran it too long on some oil changes in the past, and then contributes to cam wear I believe. From what I have heard the cam wearing is pretty common on these machines.
Does anyone have the specs on the valve clearance for me? What is it supposed to be?

 

Alrighty, I yanked that camshaft out since I was almost that far anyways. Sure looks like the middle lobe worn bad, but I don't have a good shaft here to compare it to. I will have to stop in at the dealer tomorrow. I attached a pic of the shaft. The tallest diameter of that center lobe is 1.206". The intake valve clearance was about .002" and the exhaust valves were .009" The rocker arm contact that rides on the center lobe was also a bit rough, I don't know if that needs to be replaced of if I can just polish it up to reduce wear.

Actually, Im too stupid to figure out how to post a pic here, so here is a link to the picture:
http://s30.photobucket.com/albums/c3...urrent=cam.jpg

 

Hi, according to clymer manual, the canshaft lobe height should be 1.288 to 1.292 on both intake and exhaust lobes, with a service limit (wear limit) of 1.276. valve clearance .006 in. Hope this helps.

 

If your exhaust lobe is worn off, I would also replace the rocker arm as well. I would also make sure the replacement cam has the upgrade. The newer HO cams have enlarged oil return holes and I believe more of then as well. Also don't overload the decompression spring on the new cam on install.

 

If you can see any wear on the lobe it is worn out you should also replace the rocker arm for the exhaust.

 

Thanks for the help guys. I ordered the camshaft and rocker arm yesterday.