Help regarding performance issue following boss drive install

[scsc7211]

Hey all,
I have a ZX-50 that I have desrestricted by soldering the green wires on the CDI. I ran the scooter for about a year with the CDI derestriction and an unrestricted boss drive that was installed when the scooter was originally purchased. The scooter had very good pickup all the way to a GPS-indicated top speed of around 38 mph (43 mph indicated on the speedometer).

Last night, I installed a boss drive that I purchased from Scooter Assassins on eBay that is slightly (~2 mm shorter than the other derestricted boss drive). I have noticed that my top speed has increased, especially downhill to about 48 mph indicated, but I have lost much of the midrange power from about 25-40 mph.

Would this be expected by installing a shorter smooth boss drive? Also, is there anything else I could change to recover some of the mid-range punch that was lost? (Variator/weights/carb jet) Otherwise, should I just return it to the old boss drive?

[Triesandluth]

It's the shorter boss.  I run a 37mm in my Super Nine.  The 38mm gives me great low and mid range performance,  but the extra millimeter keeps the belt from riding to the highest possible point on the variator,  at least for me.  I checked it by marking the variator with permanent marker,  then taking it for the exact same ride with each boss drive.  That's how I saw how far the belt rode up.

[0BARK4322]

Should have been the same length

[zombie]

No. The ZX is an odd ball. The correct boss is 2mm shorter than all the others.

To get that mid range back install a Malossi RED control spring in the rear pulley-s, and a set of 5 gram rollers.
It'll take off like a rocket.

The best money I ever spent on mine is the Jasil Variator (top racing) They list for 100.00 but you can get tham for 60.00 if you shop around or open a dealer account somewhere.

[0BARK4322]

Last night, I installed a boss drive that I purchased from Scooter Assassins on eBay that is slightly (~2 mm shorter than the other derestricted boss drive).
[/quote]If it is the same length as the restricted one, why would he lose mid-range power

[zombie]

The ZX is an old bike. There is no telling what was in there to begin with.

What happens is with the shorter throw of the pulley the rollers reach the top of the ramp that much sooner. That kills the mid range. BUT with the shorter boss, and lighter rollers it goes back to acting like all the other bikes. It just hits top speed quicker.

I'ts a goofy thought process in design but in playing with it I figured out what the engineers did. The short boss works better.