Modern Vespa

can anyone help me
i mounted a j costa variator on my vespa
and i got a slipping belt when it turns stationary
when i increase the rpm's the slipping stops
i've inspected the vario and it's just like the belt is too long


anybody had the same problem?

Well, there are a couple potential issues here.

1) Are you positive you wedged the belt deep into the clutch before torquing down the variator? This is a critical step, as otherwise the belt will separate the halves of the variator and you won't be able to torque it down properly.

2) Are you sure it's actually slipping? One of the characteristics of the J Costa variator on the 250 is that it spins up the RPMs higher before the clutch actually engages. When it does finally engage, it does so with fairly considerable force.

3) The J Costa for the QUASAR 250 engine is, by most accounts, a disaster waiting to happen. The brass bushing at the conical end of the J Costa variator will wear down against the steel washer at the end of the crankshaft (just inside of the outer pulley half) which will cause the inner half to get closer to the outer half than it should... which leads to the belt riding higher in the pulley, which in turn leads to the belt eating into the engine case and then ripping out the oil pan gasket. This is, at this point, a fairly well-understood phenomenon.

Seriously, I strongly recommend removing the J Costa and replacing it with either stock or possibly the Polini variator. The J Costa has proven itself to be unworthy in this particular application.

1) it wasn't necesary to wedge the belt into the clutch i could mount it like it was
2) i am pretty sure its the belt that is slipping it makes a squeaky sound
and it makes a lot of heat

now i have mounted my original vario again

could it be that the belt is too streched after 5000KM?

1) it wasn't necesary to wedge the belt into the clutch i could mount it like it was
2) i am pretty sure its the belt that is slipping it makes a squeaky sound
and it makes a lot of heat

now i have mounted my original vario again

could it be that the belt is too streched after 5000KM?

Belts DON'T stretch at all. They are reinforced with kevlar fibres. They just wear on the outside edge. If you look in the appropriate service manual you'll find a minimum belt width dimension.

Jess, I had this happen on my MP3 250 documented in a thread on the MP3 forum. Tuscon Rider caught his and his mechanic added a second washer and he had no more problems as if it wore to a point and quit wearing or the wear is now between the two steel washers and not a factor. Mine was replaced by J-Costa and I was told by Matt at Scootertrap that they had some wrong material I have put about 700 miles on it and plan to open up soon to see if wear is occuring. Performance indicates it is not. Miles are coming slower as most of the time I now ride my 400. I think Tuscon Rider also now has a replacement running on his MP3 250.

J-Costa appears to be responsive to issues and modifies their product as they get feedback. This has been the case recently on the bell shape for the 400 engine as users told them they did not get the uplift in performance the 500 engines do even though Piaggio uses the same variator. Recently 2 European users have received the new bell for their MP3 400's and report great performance.

Granted their is some (perhapas a lot of) pain involved for those that like me shredded a belt on a back road 130 miles from home on a Saturday night and also had the cost of replacing the gasket. Sometimes we pay a price for trying to get improved performance with aftermarket parts. This is part of the path that moves things forward and if J-Costa is willing to replace the product with a change to hopefully eliminate the problem I am willing to work with them. The performance uplift for the MP3 250 is amazing and the problem can be and possibly is solved.

actually, it's 100% required in any variator reassembly to wedge the variaor belt in the clutch ramps. Absolutely necessary, regardless of the make/model of variator.

If you did not do this, you improperly reassembled your transmission.

The belt doesn't stretch. From your description, you've reassembled it incorrectly and may encounter performance issues and also may cause some damage to tour transmission.

That's good to hear, and I'll be really interested in hearing a progress report later.

Before I can recommend the J Costa for the 250, though, I really want to hear some more specific detail about what material they changed from and what they're using now.

Oz is right, the belt arrangement on the 250 is such that it absolutely, positively must be wedged into the clutch. There's no question about this. Otherwise, when you torque the variator down, the belt will be pinched between the variator halves and you won't really be torquing metal to metal.

If that's not the case, then your original assessment about having a belt that's too long may be the case. The belt doesn't stretch, though. Was this a new belt? Was it the belt that was already on it? Can you tell us more about the origins of the belt?

it is the original belt
5000km or 1 year old


thanks for all the feedback