Polini Variator/Belt Second-Gear Start Issue

Does your Spree/Elite already run great, and you're trying to make it quicker/faster? Need a monster motor swap? Discuss your ideas here.

Moderator: Moderator

Post Reply

How Are Belts Measured?

Around the circumference.
3
100%
Along the inner toothed surface.
0
No votes
Midway between.
0
No votes
By the number of additional holes I pierce after Holidays
0
No votes
 
Total votes: 3

User avatar
Wheelman-111
Moderator
Moderator
Posts: 11319
Joined: Wed Oct 22, 2008 5:09 pm
Location: Deepinnaharta, Texas

Polini Variator/Belt Second-Gear Start Issue

Post by Wheelman-111 »

Greetings:

Recently obtained Polini Vario and Polini Kevlar belt, size nominally 655x16. Once underway, the Polini ramp profile is flawless, putting Flash's Prodigious Contessa smack-dab in the middle of its peak power anc keeping it there.

It's the getting underway part that's the problem. The belt felt a bit tight on installation. Comparison with the stocker revealed lengths too close to call - no shorter, but also no longer. It's not terribly wide - certainly less than the 16mm label - maybe 15.1? - but I didn't re-measure to be sure and that's from memory. Still, it was wider than my well-used stock belt. How are these things measured, anyway? The circle will be longer around the top than down along the teeth... :?:

Anyway my issue seems to lie up front. With the variator installed, the pulley doesn't seem to open as wide as the stocker . I tried inverting the 3 ramp guides - one side's thicker - but they wouldn't go on that way. Consequently the belt rides a bit above fully-bottomed in the front, and therefore about 3/16 from the rim of the driven pulley. That makes for a slow grind up to about 15 mph, above which performance is as described.

Evidently I need a narrower, longer belt. I contacted the vendor to see what my options are. Obviously they sent a belt that doesn't work as advertised on the intended scooter. However I did install and put some miles on their pricey belt. No response so far.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
teeoce
Goped
Goped
Posts: 87
Joined: Mon Jun 23, 2008 10:12 pm

Post by teeoce »

I thought that you mentioned before that the problem was on the rear pulley? That the belt was too thin and rode too low on the driven pulley?

In any case, exactly what parts did you install with the aftermarket variator?
User avatar
Wheelman-111
Moderator
Moderator
Posts: 11319
Joined: Wed Oct 22, 2008 5:09 pm
Location: Deepinnaharta, Texas

Polini Pulley Problems

Post by Wheelman-111 »

Greetings:

The rear pulley is bone-stock SA50. The clutch is also Polini, though I don't think that it matters. I just recently installed the Polini variator and it came along with a new boss and that weird Polini belt. "655mm" it says, but it's not that long. If it was, I think I'd be almost OK. The crank boss appeared to be identical to the stock one.

At first I mistakenly believed the problem to be at the rear pulley. Closer examination revealed the belt is not quite tight against the front boss, and can't get down any lower due to mismatch between the space between the drive pulleys and the belt width. The Polini ramp plate is more "domed" than I recall the stocker being.

I do believe the front pulleys on the stock variator would let the Polini belt down a bit further, freeing up some length out back. Not sure if even that would be enough without also lengthening the belt. In any case I can't test because I sold my stock vario and its replacements.

Shimming out the boss - to open the pulleys wider - isn't a good option because there'd be even less of the short splines for the starter pulley to "grab". I haven't checked to see if there's a way to make the ramp plate ride further back on the crankshaft, freeing up some space that way. Finally I have ordered a stock Gates belt to see if that's the problem.

I'll try to post some pics tonight. I'm hoping to sort this out before Flash II is ready for installation.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
User avatar
Wheelman-111
Moderator
Moderator
Posts: 11319
Joined: Wed Oct 22, 2008 5:09 pm
Location: Deepinnaharta, Texas

Further Investigation

Post by Wheelman-111 »

Greetings:

Further investigation revealed...

The Polini belt's too doggone short!

It runs the circumference of the driven face when I string it on. However bolting up the Drive pulley causes the belt, which is only 15mm wide brand-new - to come off center by a few mm, and pulls it down a quarter-inch from the edge of the back pulley.

I've seen pics of Polini variators online that show a little thrust washer among the parts arranged for the photo display. I didn't see such a washer in my kit - missed & threw away by mistake? or just never was there. Just a few hundredths would open the pulley enough for the belt to drop all the way down...Only worry is the half-bite of the pulley on those splines.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
User avatar
scooterwerx
Elite
Elite
Posts: 894
Joined: Tue Oct 07, 2008 11:43 pm
Location: redlands, ca

Post by scooterwerx »

hmmm i think im going to order the malossi belt for the zuma, i already have it for my aero, it rides all the way up like it should...maybe polini belts run short?
User avatar
Wheelman-111
Moderator
Moderator
Posts: 11319
Joined: Wed Oct 22, 2008 5:09 pm
Location: Deepinnaharta, Texas

Bosses and Pulleys and Belts (Oh, My!)

Post by Wheelman-111 »

Greetings:

I held it up against the stocker when I installed it. It appeared to be identical in length, and measured only 15.0mm wide last night. (It might have been 15.1 or 15.2 when delivered... I don't exactly recall.)

The crank pulley boss also looked identical in dimension to stock. It seems to me that the extra tightness between the drive faces has to be due to the different ramp plate. This would indeed require a longer-than-stock belt, which the Polini ain't. :(

I emailed Scooter-Center twice now with no response.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Post Reply