Bogs down at 5000rpm By scraggs (Read 1,245 times)

[scraggs]

I purchased a Jonway yy50qt-21 as my first ride...my mistake I know.  Regardless, I put a new carburetor on and got her running good.  A couple of weeks ago it started slipping during takeoff and I ordered a new clutch assembly and belt.  Put the new assembly on and belt (which is literally twice as wide as the old one) and took off down the road.  The engine didn't run as high on the rpm as it use to, but still got up around 40 mph.  My neighbor came over and suggested adding a bit of sea foam to the gas to help.  I obliged and now the scooter takes off great until the engine hits 5000 rpm and then it bogs down completely.  Scooter won't go above 25 mph and engine almost cuts out completely.  I've replaced the gas but no help.  Any suggestions?

[seanstr]

It's possible the new clutch has strong spring than old one, or the belts needs break in time. Mine was doing this at 45 mph. The warmer weather helped my 125cc. Not sure about 50cc so much.


Do one change and check results.

[scraggs]

I removed the belt and ran it. The engine did not bog down at all. That lets me know the engine isn't the problem. I placed the old belt back on and it is has no tension. It sits on the spacer bar on the front variator. Did I mention the old belt is half the width of the new belt. Is that normal? Did they used to use thinner belts? The bike is a 2009 and I don't think anything new has ever been put on it.

Regardless, I put the new belt on and it has quite a bit of tension, but it causes the engine to bog down at 5000 rpm.

Sorry for all the questions. I'm quite new at this and may have to take it to someone.

[tvnacman]

tell us how you changed/replaced the belt. Please provide details, we can not see what you got or see what you have done.

John

[scraggs]

Thanks John,
I used an impact wrench to remove the variator and the clutch. I checked the roller weights and there was quite a bit of dust in the housing. I cleaned all the dust out with brake cleaner and wiped it down completely and replaced the roller weights. I slipped the front variator back on and replaced the spacer bar.
I then took the old clutch and bell off. I squeezed open the new clutch with my fingers and placed the new belt about 1/2" into the clutch groove. I slipped the clutch back over the bar and onto the front spacer bar. I then proceeded to put the rest of the front variator together. The outside disc on my variator has teeth because it is attached to the starter. I placed the the outside disc on and then the fan. I squeezed the belt a bit so it wouldn't be directly on the spacer bar and replaced the nut on the variator and the clutch.

I then started the engine to watch what happened. The front variator is pushing the belt higher as the rpm's get higher. The belt actually reaches all the way to the top of the variator, (about 1/8" from the top). The clutch engages as the rpms get higher and the spring is doing it's job and the clutch assembly is allowing the belt to sink lower down.

It just won't allow the engine above 5000 rpm.

[scraggs]

I ordered the new belt from monsterscooterparts.com. The website said this is the correct size belt 729-17.7-30 50cc Scooter CVT Belt. The old belt does not have the same type of numbers and I can't seem to find the right belt size for the scooter anywhere online. The numbers on the old belt are two separate numbers. 15290 and 4816 MX 179.

[jct842]

Fuel/air requirements are different for load and no load. Do a plug chop. If the problem happened after sea foam, that may have changed the mix of air/fuel.1