How to Replace a Vespa Engine with a Motorcycle Engine
A motorcycle engine is much more powerful than a Vespa engine. You will find that replacing your Vespa engine with an engine for a motorcycle will immediately give you bike a lot more power and allow you to be able to get a lot more speed and overall horsepower out of it. Make sure that you understand what is involved with taking the Vespa engine out and putting the motorcycle engine in.
Step 1 - Remove Side Cowl
You will need to make sure that you have your bike stood up on its side. It is also a good idea for you to get your jack stand wedged underneath the rear part of the frame of your bike. This will need to be done so that you can lift your rear wheel off of the ground. If your bike happens to have a plastic bumper, then you will need to go ahead and remove it to avoid it getting damaged.
Step 2 - Draining Oil
Draining the oil for your bike for engine removal is not completely necessary. However, you may find that you will experience a little bit of leaking depending on how your engine is positioned. In order to save yourself the time and hassle of draining the oil, you can simply place a drain pan underneath the area that you experience any leaking, if any.
Step 3 - Disconnection
You are now ready to begin disconnecting things in order to successfully remove your Vespa engine. You will begin with the gear selector. It will typically come of fairly easily and in one piece with the cables of it still connected. Once you have done this, you can move on to the control cables. You will need to remove the throttle, choke, clutch as well as the rear brake cables.
Step 4 - Rear Brake Arm
You will find the rear brake arm right beneath the rear shock mount. It will have a 13mm bolt that has a hole in the middle of it. You will need to loosen this nut on its outside face and then pull the cable through. Use your flathead screwdriver to remove the pivot bolt. The cylinder head needs to be removed with your 13mm socket so that you can pull the studs off.
Step 5 - Motorcycle Engine
Once you have your Vespa engine removed, you are ready for the motorcycle engine installation. You will need to install it into the cradle. You will do this by lining it right up to the motor mounts and simply bolting it in place. From there, you will bolt the engine and carburetor together and attach the cables going from your choke and throttle onto the correct locations on your carburetor. Now, finish up by bolting the header pipes onto the engine and then get your muffler and header pipes bolted on securely.