Gearing configuration for PX - Pinasco 177 - 8inch rims

Hello,

I am considering the following setup for a 58 (largeframe) Vespa VNA with 8 inch rims:

P125X engine with Pinasco 177 - Mazzuchelli racing crankshaft - 28 carburetor - sito plus exhaust.

What modifications (next to migrating from three to four gears) should I do to the gearing? Do I opt for a (cosa) clutch with reinforced springs? How many cogs would be needed (23 - 24)?

Thanks for your help

Yes, I would like to stick to the 8 inch wheels.

Original von Driezza:
Take a new rear brake plate for 8 inch wheels, put the rear brake plate for 10 inch weels on it and drill new holes in the 8 inch one, so they match with the holes on the 10 inch version. Install the rear brake plate and new rubber gaskets (matching the 8 inch brake drum inner diameter). Put the rear brake drum on it. Done.

Won’t work., this might.
PX125 doesn’t have a brake-plate, similar to the type motorcycles have. The brake shaft and the pivots for the brake shoes are incorporated with the motor casing, and only a thin steel plate dust cover

You are better of if you fit a modified 8” rim to a modified PX brake drum.

  1. Check the offset of the 8” rim, if it is the same as a px rim.
  2. Measure the inside dia of 8” rim, should be some mm less than 200.
  3. Turn of the cooling ribs on the left side of the brake drum, and the outside to the same dia as measured above, make a radius to mate the corner radius on rim.
  4. Turn a hole in the rim, to the same dia as brake drums left side, were the fins are turned of.
  5. In what is left of the mounting tabs of the brake drum, you drill and tap 2 off M6 holes, side by side, (5 pairs). Loctite 10 off M6 Allen screws in these holes, so the treads are exposed on left side.
    Drill mating holes in the rim.
  6. On the right rim, weld 5 off M8 x 13 mm treaded pieces, and drill 5 off 8 mm holes in left rim to match.
  7. Cut out both brake drum and rim for air valve.
  8. Assemble with 10 off M6 & 5 off M8 Nyloc nuts. Nuts and washers on the left side.

Leif

[:bounce:] [:bounce:] [:bounce:] [:bounce:] [:bounce:]

Belgium… Leif… Belgium

Are you going to keep the 8" wheels?

You are mad if you keep the 8" wheels. and you may have trouble mating am old hub to the px engine. why do you want to keep the 8" rims?

Hi,
as the P200E owners sometimes shortens the fourth gear by using the early PX125 fourth gear, you might be able to use a P200E top gear-wheel, that would bring your fourth up approx 3 %.

A 24/63 primary drive gear combination (Malossi)
An early P125 and P150X with P200E high gear
A 3.50 x 8 rear tire size
Results: Ratio–> 12.47 8.85 6.30 4.73
RPMs 1st Gear KPH 2nd Gear KPH 3rd Gear KPH 4th Gear KPH
1000 5 7 11 14
2000 11 15 22 30
3000 16 23 33 45
4000 22 31 44 61
5000 28 39 55 76
6000 33 47 66 92
7000 39 55 77 106
8000 44 63 89 122
9000 50 71 100 137
10000 56 79 111 152

Leif

[:dance1:] [:dance1:]

Original von Driezza: Take a new rear brake plate for 8 inch wheels, put the rear brake plate for 10 inch weels on it and drill new holes in the 8 inch one, so they match with the holes on the 10 inch version. Install the rear brake plate and new rubber gaskets (matching the 8 inch brake drum inner diameter). Put the rear brake drum on it. Done.

you might have left out some minor details…

Leif

[:bounce:] [:bounce:] [:bounce:] [:bounce:] [:bounce:]

Original von diablo: You know your stuff Lief thats impressive. For all that trouble though Driezza i'd modify a set of forks and have a bike that doesn't handle like a shopping trolly with a limited choice of tyres! You wont need to worry about gearing either[;)]

Yep, sounds a lot simpler and gives better handling, as you say, but I saw it as a challenge that I couldn’t resist.

Leif

[:bounce:] [:bounce:] [:bounce:] [:bounce:]

Original von Driezza:

Diablo,

there are plenty of largeframe (8 inch rims) combined with tuned PX engines over here and they al do very well. Converting to 10 inch rims in my case would mean getting another steering column and another front mudgard on it as well. I do not want to do that.

OVER WHERE???

Leif

[:bounce:] [:bounce:] [:bounce:] [:bounce:] [:bounce:]

This is as high you can get,according to

http://www.scooterhelp.com/tuning/gearing.html

A 24/63 primary drive gear combination (Malossi)
An early P125 and P150X standard gearbox
A 3.50 x 8 rear tire size
Results: Ratio–> 12.47 8.85 6.30 4.73
RPMs 1st Gear KPH 2nd Gear KPH 3rd Gear KPH 4th Gear KPH
1000 5 7 11 14
2000 11 15 22 29
3000 16 23 33 44
4000 22 31 44 59
5000 28 39 55 74
6000 33 47 66 89
7000 39 55 77 103
8000 44 63 89 118
9000 50 71 100 133
10000 56 79 111 148

Leif

[:dance1:] [:dance1:]

You know your stuff Lief thats impressive. For all that trouble though Driezza i’d modify a set of forks and have a bike that doesn’t handle like a shopping trolly with a limited choice of tyres! You wont need to worry about gearing either[;)]

How do you modify the back wheel to fit?

Take a new rear brake plate for 8 inch wheels, put the rear brake plate for 10 inch weels on it and drill new holes in the 8 inch one, so they match with the holes on the 10 inch version. Install the rear brake plate and new rubber gaskets (matching the 8 inch brake drum inner diameter). Put the rear brake drum on it. Done.

Original von diablo: You are mad if you keep the 8" wheels. and you may have trouble mating am old hub to the px engine. why do you want to keep the 8" rims?

Diablo,

there are plenty of largeframe (8 inch rims) combined with tuned PX engines over here and they al do very well. Converting to 10 inch rims in my case would mean getting another steering column and another front mudgard on it as well. I do not want to do that.