You can install a motorcycle engine into your snowmobile and still get the speed and functionality out of the unit. With a few engine mount modifications and some adaptations on the intakes and exhaust, your machine will be up and running like new. The engine compartment is designed for the snowmobile engine mounts, it would be good to know how to weld to make new engine mounts inside the engine compartment to house your motorcycle engine properly. These mounts can be made and welded to the frame with steel materials, and if positioned properly, will leave the standard engine mounts free of obstruction so they may be used again in the future.
Step 1 - Build Your Engine Mounts
Look at the engine compartment in your snowmobile, and determine where your motorcycle engine will have to be mounted. Once you know where it will have to sit to line up with the drive shaft, begin to build your engine mounts using your welder. Be sure that the engine mounts are secured to the frame in a solid position to prevent them from breaking loose under torque.
Step 2 - Mount the Engine
Once the mounts are in place, you will then secure your motorcycle engine into the compartment. Once the engine is in place, inspect the drive shaft and crank shaft areas of the snowmobile and motor to see how they will have to come together. You may have to modify a gear casing to bring the two together, which can be fashioned from gears and metal plates to hold the assembly into place. On some models, the shafts may fit together without any adding mechanics needing to be added.
Step 3 - Run Your Gas and Electrical Lines
Use your wire tool and caps to attach your motor to the on board battery system. Snowmobiles can run on a higher voltage battery system than a motorcycle engine. In this situation you will have to modify your battery mounts for the motorcycle battery to fit properly, which will prevent it from moving while the vehicle is in motion. Use wire caps to tie your wires together from the battery connection to the engine to supply your electrical current. The gas line will simply tie into the engine as normal, as these are generally a standard size hose that is universal among smaller engines.
Step 4 - Run an Exhaust Adapter
The last step is to tie your motorcycle engine exhaust into the existing exhaust lines of the snowmobile. You can find adapters to run from one size pipe to the other, which will tie the engines exhaust from the manifold to the snowmobile exhaust port. These couplings are very inexpensive and can be installed and sealed tightly with pipe gaskets. Once you have all the needed connections in place, you will want to adjust the carburetor and idle speeds until it runs smoothly. Be sure to check and replace fuel and oil filters if your engine uses them to ensure you get the best end result from your motorcycle powered snowmobile.