My little sister got a Yamaha Moto 4. It has an 80cc engine. When we got the quad it had been sitting for 12 years, but it had been covered so nothing had to be done except an oil change. But for some reason it feels like the clutch is slipping but here is the strange part; if you get on it and really rev the engine it won't want to move but if you let off the throttle a little it will go just fine...Infact if you try giving it about 1/2 throttle or so and then let off slightly it will almost jerk it gets such a burst of power....I am confused. I am not sure on the exact year, but I believe it is from the 80s.

EDIT: Also if you slowly get on the throttle it will do just fine until you get into the higher RPMs again...The quad doesn't lack power in the lower RPMs at all...Just the higher.

 

Bump

 

If this is the correct model you have,could be the friction plates are glazed/oil soaked over the years causing the slipping. I've found plenty of different machines like this.Depending on wear,you may can get by with scuffing them up with emory cloth as some have done,or just simply replace them.Save 20% on 1986 Yamaha YFM 80 - BADGER 80 OEM Clutch Parts | MotoSport

 

Thank you, I appreciate it. I am only 17 and personally drive a manual dirt bike, so semi-automatics are new to me as far as the internals go.

 

You have to start somewhere and this will help you learn if it needs to be torn down.http://www.ebay.com/itm/Clymer-Repair-Manual-for-Yamaha-YFM80-Moto-4-YFM80-Badger-YFM80-Raptor-/291379597149?hash=item43d793cf5d&vxp=mtr

 

Thanks for the manual, yes it will. I am used to simple Briggs & Stratton flathead engine and my chinese Honda clone engine. I have already had to tear the Honda clone apart because it wouldn't shift. It turned out to just be a loose bolt...I ended up being impatient and using cereal box gaskets on everything but the head which I replaced with a new one. It still runs and drives today and it has been many many months now. I wouldn't dare do that on a name brand engine though. Too many things that can go wrong. The thickness of the gasket being one of them.

 

Guilty on this myself on some antique cycles,but used sheet gasket material. If you ever have to make any more gaskets for anything, most auto stores have it and it seals a little better than cardboard.

 

Yeah, I should have used gasket paper. But it was my first time and I didn't want to ruin gasket paper. It took me several cereal boxes to get it right. Finally I decided to coat the surface with oil and stamp it. That also took several tries but once I finally got the right amount of oil it worked perfect.

 

hey matt8110 what happened to be this problem because i have the same problem with my moto4 yamaha 80cc. when on stands wheels spin and when on ground does the exact same thing yours does

 

As said above it sounds like clutch friction plates. You can try to adjust the clutch, or you may need to replace the plates.

Adjustment is pretty simple. Pop the rubber plug (if its still there) on the left side case. Loosen the nut that is threaded onto a phillips head screw. Lighten the screw until you feel resistance, and then loosen it a 1/8 turn. Tighten the locking nut.

If this doesn't work, you need to pull the clutch. I just ordered plates and plan on doing the replacement this weekend.