Combining two single cylinder engine using chain in the crankshaft - Is it Reliable?

Question

I want to make a project of combining two Honda GL200 by connecting the crankshafts using a chain and putting the main engine (the engine that has the transmission thingy) behind the slave engine (the engine that doesn't have the transmission thingy)

It'll look like this :

The purpose of this project is to make a dynamic sounding engine. You can adjust the engine sound to your liking, by adjusting the chain without having to change the whole engine system (valves, timing, shafts).

1. 180 degree Ninja 250 Sound
2. 360 degree CB200 Sound
3. 270 degree V Twin Sound

The question is,

1. Is it reliable?
2. What is the pros, cons, by using this way, instead of welding the crankcase?
3. Are there any successful project out there, chaining two 4 stroke single cylinder engines?
4. Will the engine sound the same as a 2 cylinder engine, or will it just sounds like 2 engines running differently? I mean, because of the chain's tension, will the shafts sync as good as welding them?

Answer 1

Assuming you can fabricate a frame to hold both engines, this should work fairly well. There are several factors you should consider about linking two engines with a chain.

1. If you retain the ignition system of each engine independently, you can change the relative timing of the engines with ease. So don't worry about the correct timing, just find it experimentally after you have it running.
2. Each motorcycle engine is unique, but many Japanese engines have a dry cover on one side for the permanent magnet alternator. With custom adapters, you can couple the engines this way and use a traditional chain and sprocket arrangement. This side of the crankshaft isn't meant for transferring power however. A better arrangement would use a custom cover on the clutch side to somehow link the engines inside a common oil bath. The clutch generally rotates at less than 1/2 the engine RPM. This would make the project safer and more reliable, as the engine chain is not rotating as fast.
3. You will need to synchronize all the carbs together on both engines.
4. The rear engine crankshaft has double the normal the power going through it in this arrangement. It may work fine, it may snap instantly.
5. The rear engine clutch and transmission will have double the power going through it. It may work fine, it may fail quickly.
6. The front engine clutch and transmission can be removed, as it will no longer serve a purpose.
7. The exhaust of the rear engine essentially would run right into the front engines intake. To avoid this, the rear engine needs a custom exhaust manifold
8. Since you are using two air cooled engines, the rear engine requires a fan for continuous operation or at least a very air scoop. Many Buell air cooled twins were sold with engine fans on the rear cylinder, you can probably adapt their solution to work.
9. Given the amount of heat you'll be packing to a very small area, it probably is necessary to add external oil coolers to each engine.

Answer 2

You need to investigate the size of chain necessary to transmit the power of the engine and also consider the speed at which it is moving - this will not be the same conditions as the chain from the gearbox to the rear wheel.

Answer 3

1. Is it reliable ?

Yes. It will be as reliable as the chain itself.

2. What is the pros, cons, by using this way, instead of welding the crankcase ?

Welding will require precision engineering. The chain setup doesn't.

The chain configuration will require lateral space though. The welded configuration requires a smaller footprint.

3. Are there any successful project out there, chaining two 4 stroke single cylinder ?

Depends on your definition of success but it can be made to work.

4. Will the engine sounds be good ? I mean, because of the chain's tension, will the shaft sync as good as welding the shaft ?

This depends on supporting mods like the exhaust design.