Has anyone on here experimented with converting their existing 2-stroke motorcycle engine to run on diesel? I think that I would like to try going this route before doing the Yanmar-clone conversion, unless someone who knows more about engines can tell me that it would be a waste of time and money.
It would not necessarily be a real diesel engine because the compression would remain the same and it would still retain the carburetor and spark plug. It would be closer to an RC glow engine. But ideally it would still run well on diesel and one of the main appeals is that it would look almost stock on the motorcycle and everything would bolt right up.
There are plenty of videos on YouTube of people running weed wacker, leaf blower, lawn mower, and other small 2-stroke engines on diesel. The main issues seem to be that they cannot really start on diesel, they can only run it once they get up to temperature, and they make a lot of white/oily smoke. Some people who actually tried fiddling with the carburetor were able to tune most of the smoke out, at least at idle. Which is not bad since some 2-strokes smoke a bit even when running on gas.
From my understanding, diesel engines have high compression to create high temperature in the combustion chamber, higher than in gasoline engines. So my idea is to simply raise the temperature in the combustion chamber while retaining the stock compression ratio. One way to go about this could be to just get the hottest spark plug possible and see if that would be enough. Right now the engine I have has the third hottest heat range spark plug, so I could go two ranges hotter. This would raise the temperature of the tip of the spark plug by about 150-200C. This may or may not be enough to burn the diesel better under compression. I could also get a longer spark plug that would protrude into the head more, which would raise the compression slightly. But again, I am not sure how much of a difference it would make. Also, I doubt that it would be good for the spark plug or for the head cover. I am also not sure if the hotter spark plug would burn out quickly or if they are pretty tolerant of higher temperatures.
The second idea is to replace the spark plug with a glow plug.This would make it even more similar to an RC glow engine. While this could potentially make the engine run well, there are a few issues that I would need to figure out. First is that glow plugs cannot be constantly powered or they will burn out pretty quickly. I would try to run it constantly but at a lower voltage, as long as it still gets hot enough. But I am still not confident that it may not burn out even then. The other option would be to run it intermittently, maybe for ten seconds every few minutes or something like that, since they stay hot for a while. This may work, but it would be more complicated to set up. Another big issue is that glow plugs need quite a bit of current to heat up while most of the old motorcycle powerdynamos only output about 8-12A at 12V. So running it at lower power or intermittently would really be the only options anyway and even then I am still not sure that it would not drain the battery.
After figuring out the combustion, I would of course still need to adjust the carb to hopefully make it run smoothly. I would probably also adapt an electric starter to the engine somehow since it would most likely be a pain to kickstart on diesel, except maybe with the glow plug.
There are also companies that converted 2-stroke engines to diesel 'properly' for military needs and such applications by making custom heads for them to raise the compression (although they usually still retained the spark plug to aid with the extra heat). But that would be a lot of custom work and money, not to mention I doubt that these old 70's 2-stroke motors could handle raised compression, at least not for long.
I would appreciate hearing any input or advice. Or just tell me that this is all a stupid idea that will never work well so I can go directly to using a diesel motor.
Thank you for reading.