Low torque, bad acceleration

[4kmotofino]

I've recently acquired and 50cc Motofino with 4,250 miles on it. The motor runs great, clean carburator etc. however, I'm experiencing crappy take offs and really bad acceleration.(with a 200lb rider) :scoot2:
I've replaced the variator and weights(both were in terrible condition when i bought it.) as well as a new belt. I've had the scooter for a couple months now and i ride it regularly. I recently checked the variator and weights and they looked normal. However the belt had a little wear on it. I think i might have the wrong belt. :stumped:
I've done some internet searches and I've found mixed information on the correct belt size for this model. :banghead:

Questions:1) Is there a way for me to be absolutely sure what the correct belt should be? (I.E. measuring a shaft in the CVT?)
2) At 4k miles, is it time to put in some new springs in my clutch? Or even a whole new clutch? I'm wondering if it could be contributing to my acceleration issues. :help:

thanks in advance for any assistane you provide. This looks like an awesome forum and good place to get some real answers. :cheers:

[90GTVert]

:welcome: to the forum!


I'd start by looking at the belt at rest. It should sit near the center of the front pulley and near the outside of the rear pulley. If not, remove the fixed half/fan so you've got the variator and drive boss installed up front still, but nothing that will squeeze the belt upward in the pulley. Now does it sit on the drive boss and near the outside of the rear pulley? If it doesn't at this point, you may have a belt that's too short. If it does then, but not with the other half of the front pulley installed, the belt is either too wide or you may need a spacer washer to get the best take off "gear". Sometimes a spacer will drop top speed, so it can be a trade off. Not always. If you do try that route, the shim needs to be the same diameter as the drive boss or just barely smaller. It should be able to fit through the center of the variator.


Check the belt first, then perhaps check the clutch. If the clutch springs are weak you should notice that it takes very little RPM increase over idle for the scooter to try to go. You shouldn't need to replace anything in there at 4000 miles, but it wouldn't hurt to have a look and make sure it's all clean. If you dive in that far, might wanna clean the torque driver for good measure. Here's a vid that goes over pretty much everything in detail...

[4kmotofino]

Thanks for the reply 90GTVert. Here is an update.
We took off the CVT cover and dove in. When I say we I mean myself and my buddy. He buys broken and used peds, fixes them and resales them so hes fairly knowledgeable. Still new to the business so he hasn't seen this problem before which is why I posted here. Anyway.

The belt has a notch missing, but its still good until the replacement arrives. Its glazed and looks to be squeezed. He said that's normal for a worn belt. (669-18.1-30). For the most part, the belt appeared to be resting where it was supose to be as you mentioned in your reply.

Rollers looked good. There was a good bit of black sooty dust in the cvt. We blew it out with compressed air. Cleaned the clutch bell and the variator as you demonstrated in your video. We put it all together and took it for a spin. It had a little more take off but nothing to write home about.

Two days later when I was riding it home from work(4pm, 90 degrees and humid) it was completely crap! It wouldnt do more than 25mph on straight and level! And interesting note tho is that morning it ran 40mph,(6am 65 degrees and crisp) still had really bad accel, it takes almost a full minute to top speed on level ground.

So then we thought "maybe its a carb problem. So we swapped crabs from a much faster Peace Sport. My MotoFino had no change with the Peace Sport's carb and Peace Sport saw now loss of power using the MotoFino's carb.
"well maybe its a valve timing problem" So we pulled the valve cover and got the feeler gauges out and checked and they were within the recommended values. ( I cant remember exactly, I think .004?)
"maybe the spark plug is bad?" We checked the gap, it was correct and plug looked good. We hooked up an advanced CDI from one of my buddie's peds. It upped the revs a little bit and now it starts a lot easier than it normally does, but no change in acceleration or top speed.

I' ve been riding Moto to and from work every day and in the morning it seems to perform a little better. I think the atmosphere has a lot to do with this issue. Seems to perfer being cool.
At this point im even more stumped than before.

I got some more info on the history of this ped and found out that top half of the motor was scrapped when my buddy fixed it. He kept the orginal crank case but it needed a new head. If that matters? My thinking is that maybe its curical that the crank and head match. Is it? (50cc head has to have a 50cc crank?)
I dont know. I really wish I could solve this problem, if nothing more just as an acomplishment. I mean, it runs. Its been getting me to and from work(not on time every day, but my Boss is understanding) Its saving us money, which is the point, but I would like to be a little more safer by doing the speed limit. A ped doing 25mph on a 40mph during rush hour is just annoying to the other motorist, not to mention dangerous and Im getting tired of having to pull over to let the traffic pass.

Any ideas?

[Goosey]

You didn't say what weight the rollers are that you put in? A lighter weight, 4.5 or 5g will normally increase take off and exceleration, up hill climbing. Won't assist in top speed though.

[4kmotofino]

5gs is the weight of the rollers. Same as stock I believe.