DIY Network

Engine Upgrades: New Larger Carburetor From "Classic Rides" episode DCLR-112

	In this segment host Kevin Tetz and guest Greg West evaluate and begin modifications on the Vespa engine.
	Figure A

In the first segment, host Kevin Tetz and Greg West, a Vespa restoration expert, replaced the worn-out shocks and the brakes on the '74 Vespa Sprint Veloce project scooter. Now it's time for engine upgrades.

A Vespa engine encompasses the drive train, transmission, rear wheel, brakes, suspension, carburetor and cooling in a single unit. Within the two-stroke engine system there are no valves, camshaft, oil pump, water, drive chains or belt like in a motorcycle. The major difference between a two-stroke engine and a four-stroke engine is that a two-stroke engine detonates every other stroke. Also, in a four-stroke engine there are individual intake, compression, combustion and exhaust strokes, while in a two-stroke engine these are shared in a compression-intake stroke and a combustion-exhaust stroke.

Evaluating the Project Scooter

• The power on the project scooter is down a little, but it sounds good. The fact that it can idle without using the choke is a good sign that the seals aren't leaking, according to Greg.

  Note: Greg suggests a test that you can do on the flywheel side. You can rock it back and forth (figure A) and feel how much play is in the bearing. A little play is going to be normal because it's got to be able to move, but if it were real excessive that's a sign that the bearing is probably worn and it might require going into the engine.

• The modifications suggested by Greg include a new pump to increase the volume it puts out, a larger carburetor, a larger cylinder and a new performance exhaust.

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	Figure B
	Figure C

Getting Started

• Slide the engine onto a stand, where the engine swing arms slip right onto the stand stud, and secure it with a bolt.

• Start by removing the old carburetor (figure B).

  Note: Carburetors are referred to with a millimeter dimension. The dimension is the size of the Venturi, where air and gasoline are mixed. The size of the project-scooter carburetor is 11mm, but it's going to be replaced with a 24mm carburetor.

• Remove the bolts that hold the carburetor in place.

• The carburetor is ready to come free from the engine and be replaced with the larger carburetor, which is going to give the scooter a boost in power.

  Note: Older carburetors get some wear around the slide and that creates a vacuum loss and cuts down on efficiency. When an engine has the capability to burn more gas there's a point at which the standard carburetor must be re-jetted or replaced to let more gas and air into the cylinder.

• Place the new carburetor (figure C) back on the engine, but before it's completely installed, hook up the throttle linkage. Tighten the threads putting light, even pressure to avoid cracking the casing or even the carburetor.

  Tip: Any time you make changes to your scooter's engine, you must select the correct jets. Consult with the place you purchased your engine parts to get a recommendation on the correct jetting.

In the next segment Kevin and Greg continue with the engine performance upgrades that will give the engine a power boost.

RESOURCES :

Eazyrizer Big Blue Motorcycle Lift (Driven Gear)
Driven Gear Inc.
Website: www.drivengear.com

RaceDeck Modular Flooring (SnapLock Industries)
SnapLock Industries
Website: www.racedeck.com

Vespa Restoration Parts (Scomo)
Scomo
Website: www.scomo.net

Air Compressor (Bend-Pak)
Bend-Pak, Inc.
Website: www.bendpak.com

Stock Photos, Videos, CD Rom and Timesurfer (Piaggio)
Piaggio, USA, Inc.
Website: www.piaggio.com/

GUESTS :

Greg West
Scooter Restoration Expert
E-mail: wheelsX2@yahoo.com