Strange Problem - Engine slows down after mile

Huffydavidson said:

Check your gas cap to make sure its venting properly . When your engine starts acting up like you said , crack open the gas cap for second or two and if its goes back to normal I don't think you know what it is .. Also check the head that it torque to spec.

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ya beat me to it HD.The cap vent can get clogged. It took me an hour to figure it out the first time it happend to me. It runs for a few minutes, then starts losing power, crack the cap open and it runs great again.
Fatdaddy.

It's been a week, Maybe he figured it out.
Fatdaddy.

Metal expands when hot, making the leak larger, So,I think I agree, It's a air leak.NOW ya just gotta find it. Take a squeezbottle of water and drizzle it on both sides of the intake manifold while the engine is running, if the engine slows or stops, you have found the leak. It's a easy FREE air leak test. Just dont let yer lady catch you dumping out the catsup bottle in the sink just for the bottle, I'm STILL catching crap about that one.
Fatdaddy.

It sounds like one of your major problems is engine heat. Are you still running the stock exhaust pipe? If so you are putting a lot of backpressure on the engine as that pipe is designed for 4strokes. I would suggest getting a new exhaust pipe, one that has a 2stroke expansion chamber. If you don't want to get a new pipe, you can modify the stock one to relieve the backpressure issue. If you take off the bottom cap you can cut the metal tube as close as you can to the base. I do this to all stock exhaust and my bikes run better until my expansion chambers arrive. I also drill 2 or 3 holes in the cap to get a little better sound (but not too loud). If engine heat is still an issue, I would suggest getting high temp silicone gasket gel/goop/stuff, I used it as a gasket enhancer on my gp50 because the gasket had a dent in it from a machining error from the factory. The silicone fills the gaps in the existing gasket and I have heard of people using just the silicone as the only gasket. You can find it at most auto parts stores.

Just for kicks remove magneto cover and make sure there is no fuel mix residue or liquid around or under magnet. Probably no problem , but does not hurt to check. In my experience a very small leak at the mag seal can be ghostly because the engine will still start when cold.

vinnie said:

Hey Maniac,

I know it's been a while, but I was in a store the other day and saw an aluminum food tray and it said, "Roaster Pan" and at that moment it hit me that you meant one of those. I have no clue how I could have not realized that. What thickness do you use for making gaskets such as an intake or bottom head gasket? Thanks a lot

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The thickest ones I can find. But any size will work in a pinch.
Easy to shape and cut too.