Engine Trouble Power loss

[LeTweek]

Skyhawk 66/80 had good performance for about a year, 40-55 miles/week average.
Then I had (particularly on hills) loss of power.
I stored off the bike for a few months. When put back together, motor ran great again. Then soon after muffler gasket failed. Replaced gasket. Back to poor power. Test ride had short spurts of power at hi revs. Sprayed carb cleaner while running to see if I could find leak. No.
1) What things would you check going from here?
2) Could leaky muffler gasket have caused the engine to have more power?

 

[butre]

I would imagine it probably needs new rings with that kind of mileage. top end bearing too while you're in there

 

[bikejock]

Did you break it in properly? Usually a bad break in period can lead to power loss. If you are pushing the bike to top speeds when you first start driving it that's usually a bad break in period. My 4 stroke engine requires me to drive it at speeds of under 25 mph during break in before I start driving it at 30 mph. Sometimes with 2 strokes it helps to adjust the oil gas mix ratio during the break in. It's been a while since I had a 2 stroke but that's somewhat how I remember it.

 

[crassius]

if muffler is clogged, a leaky gasket will run better - to test, just loosen muffler a bit and see if power returns - if so, you need a new one or you need to clean the old one (info here on the board, but it is sometimes hard to get it done)

 

[LeTweek]

Clogged muffler - BINGO! Thank you Very Much!