Rajay turbos have an unenviable reputation in light piston aircraft. They've been around since at least the early 1960s and parts should still be available, if costly.
Motorcycle engines and light piston aircraft engines share two traits: They're both air-cooled and have minimal exhaust systems.
Part of the reason Rajays weren't univerally liked in aircraft had to do with their wastegates, which are sort of like a second throttle (the wastegate determines how much boost the engine gets -- close the wastegate for more boost, open it for less). Unsurprisingly, there were two main types: manual and automatic. The automatic versions frequently got out of adjustment and the manual ones typically got forgotten by the pilot. In either case, engine damage often resulted from overboosting.
A third type of installation involves a fixed wastegate. In this design, there is no way to control the wastegate but overboosting -- and "bootstrapping" (the faster you go, the faster you go...) -- can be a problem.
Nowadays, turbos in piston aircraft are relatively bulletproof, thanks to advanced engineering of the controller and better understanding of the engine's cooling requirements, and how to meet them. Typically, turbocharged piston aircraft engines either run fairly rich mixtures (the excess fuel is used to help cool the cylinders) or lean ones (up to 100 degrees F lean of peak turbine inlet temperature) in which excess air helps cool the cylinders. New turbo installations in piston aircraft typically use automatic wastegates hydraulically controlled with engine oil. Separately and regardless of the type of wastegate, operators are typically advised to allow the engine to idle for a few minutes before shutting down, allowing the turbine to spool down before oil circulation is stopped to prevent bearing damage and/or cooking the oil.
So, putting an aftermarket turbo on a motorcycle would raise a few questions:
1. How is the wastegate controlled? If manual, is there anything in the installation designed to prevent overboosting? Is there a "boost gauge" of some sort? If automatic, how is it controlled?
2. How are the carbs jetted? At low turbo output, less fuel would be necessary to achieve an efficient mixture but, at high output, more fuel is necessary.
3. When a turbo is involved, engine oil gets a workout. What kind of oil was used in the engine and how often was it changed?
4. What are the compression numbers in the cylinders? (Hint: lower compression and compression ratios will help prevent detonation at high power settings.)
I'd guess the wastegate is fixed, for simplicity and to prevent having to manipulate another "throttle." If so, is it adjustable?
Having said all that, I'd guess the turbo isn't doing all that much work in this installation and that much of the aforementioned is not a huge concern. Pay attention to the oil, oil lines, cooling and potential for overboosting. Let the turbo spool down for a few minutes before shutting off the engine. I wouldn't run it at high power in lower gears unless I was in cool weather -- keep air flowing over the heads when the turbo is spooled up.
And if you ride it at night, do tell us if the turbo housing gets hot enough to glow...
Good luck with it...
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PS: Sorry for the long post...
