4-stroke runs OK for a few miles, then starts to bog...grr.

[loquin]

Also, check that there aren't any air leaks at the intake manifold. It's possible that as the engine heated up, the thermal expansion shifted the gasket enough to cause the leak to develop.

And, as srdavo mentioned, the flywheel is also a blower - it pulls air in and forces it over the engine. The sheet metal directs the air flow, keeping the engine temperature stable. If the shroud is removed, this will interfere with your engine's temperature regulation.

 

[Alaskavan]

I'm experiencing a problem, and this thread seems like as good a place as any for it.
1. The Lifan motor on my trike doesn't idle consistently. It starts up and idles a little fast, then as it warms up, the idle falls off.
2. When the engine is cold, as I accelerate, the engine will bog occasionally until I'm doing about 20 - 25 mph.
3. Once I get going, engine cold or warm, the engine surges at speeds between 20 - 35 (perhaps it's bogging a little?). The engine runs smooth at low and high speeds.

I changed the plug, and tried running without the air filter. No effect. I'll change the fuel filter tomorrow. Anybody have any other suggestions?

 

[bughuggger]

I had a pinhole sized hole in my fuel line but it was on the place where it covered the metal nipple. So I cut the bad part off and everything was fine again. Maybe a tiny leak. Go for a thicker hose if you're goint to commute.