Sunday, November 22, 2009

Motomatic Watercooled Vespa/.....

Text and pictures courtesy Motomatic

Major Components
Vespa Grande: Frame & integrated Gas Tank
Honda Hobbit: Cases & Rear Wheel
Derbi Variant (Flat Reed): Crank, Clutch, Variator (TJT), Metrakit cylinder kit
Motomatic Exhaust: Destroyer
Motomatic Sub frame: Built by Nate out of thin walled 4130 steel tubing made to match a typical moped wheelbase of 44”.
Rear Shocks: Honda XR 75
Front Forks: Pit bike forks (last race used EBR race forks)
Front Wheel: 17” rim with a Motobecane hub with a pit bike disc affixed.
Rear Wheel: 16” rim with Honda Hobbit hub and GSXR 750 disc brake affixed.
Motomatic Powder Coating: Thank you Mike Rafter
Carburetor: OKO 21mm (changed to a 24mm)
Ignition: HP1 Puch ignition

The Assembly:
In addition to the assembly of these key parts much effort was put into how to get these parts to work together.
• The sub frame had to be offset to ensure the drive belt was aligned
• A special reed cage manifold was made to squeeze the largest reed cage (Gilardoni) within the stock mounting stud pattern and yet still have the reed pedal close as possible to the crank case and also direct flow directly into the transfer ports.
• The rear Honda Hobbit torque driver was modified so it can match the variation (movement) of the Derbi Variant Variator.
• The HPI ignition needed the taper re-machined for a good fit, the hobbit cases needed to be machined to fit the seals and Puch stator plate, and a stator plate base needed to be machined. 10 hours spent here.
• A custom seat had to be supported and fabricated. (Thanks to Nate)
• The 70cc Metrakit kit needed slight modification of the stud holes and small amount of epoxy was used on the cases to match the stock Metrakit base gasket shape. Also, a 1mm base gasket was used to keep 1mm clearance between the piston and head.

Road speed test with stock rear gears 69 MPH
Road speed test with Malossi rear gears 73.8 MPH

For more information and pictures check out the Motomatic post