I had my petcock replaced recently, because of a broken diaphragm, and afterwards I changed the oil because I figured all that revving to keep it from stalling had to be pretty hard on the engine. Put in two quarts of SAE 10w-40, just like it says on the cap.

Now I'm feeling a lot of resistance in the first half of every gear, and while going up a hill something felt totally wrong.

I tried opening my fuel cap because I read something about clogged vents, and because I'm guilty of filling up to the top... that worked for a couple miles but then it started doing it again.

Any advice?

 

SAE 10W-40 oil is standard and should be okay, it doesn't have to be motorcycle grade oil, the standard automotive stuff is okay.

For one dcarroll, after filling the crankcase of new oil, did you check the oil level sight glass at the lower right hand of the motor? Bike should be on level ground with forks straight, bike off kick stand and perfectly upright/balanced. The oil level should be somewhere near the middle, between the 2 marks.

I am not sure what you mean by a lot of resistance. Is it the bike seems to have little power at low rev's in each gear? Or is it a mechanical feeling, like something is rubbing or a gear bearing may be failing?

Sincerely, George Hostler