This one will probably stump ya

[Kurt Franz]

Lifan GY 200 pushrod engine. Bike starts fine and runs decent for about 5-10 minutes and then i start getting terrible vibration which is definitely emanating from the engine. The motor mount bolts are all there and tight. And if it were the motor mounts I would think that the vibration would be there immediately, not after 10 minutes or so. I did have an issue with the rear brake locking up, but fixed that by adjustment of the brake pedal/master cylinder rod. I am wondering if there is something internally wrong with the engine. However, it does shift completely normal and has good power. It is just that bad vibration. And when I say bad I mean bad enough where no one in their right mind would ever have bought the bike if it did this new. If i get a chance I will try and post a vid using my gopro mounted right next to the engine.

Thanks
KF

[Weldangrind]

Kurt, even though the bolts are tight, I suspect them. The mounting holes in the motor tend to become out of round, so that's where the slop usually is. Quite frankly, I'm waiting for mine to start behaving that way.

I know that others have solved this issue buy buying SAE bolts (rather than Metric) that are slightly larger in diameter, and then drilling out the existing bolt holes to suit. If you were to remove your engine from the frame and just pass the bolts through the holes, you'll likely see what I mean.

[katoranger]

I installed SAE bolts in my lifan and it made a huge difference.

[Kurt Franz]

I can see what you guys are saying, but what makes no sense is that the vibes don't get real bad until riding 10 mins or so. If it were the bolt holes it would start immediately.

At least that is how I see it