Charon wrote on 05/24/10 at 19:50:16:Even with a tach and a dynamometer, the only way to find out whether an engine has a rev limiter is to wind it up until the rev limiter operates. If the rev limiter doesn't operate, or isn't present, you have to keep increasing engine speed until some other limit is reached. You can do it with the engine unloaded, for example in Neutral. Or you can do it with the engine loaded either on a dynamometer or the road. If someone has a different or better idea, speak up.
Now, as it happens, I spent my working career as an electronics tech. Given a little more test equipment than I have, I would test the ignition box electronically. On the bike, I'd just unplug the wiring from the pulse generator coil in the stator and use an electronic pulse generator to trigger the ignition box. I would then vary the pulse generator frequency to simulate different engine speeds, and observe the spark output with a 'scope. With a little more work, that procedure could also "map" ignition timing at different engine speeds.
If I were going to design a rev limiter for a carbureted engine, given present EPA rules, I would not design a system that worked by interrupting the ignition. That's because the interrupted ignition allows unburned hydrocarbons into the exhaust. Instead, I would start retarding the timing as the engine approached redline. The timing could be retarded even to the point that the spark fired just before exhaust valve opening. The rider would never realize the limiter was working, but would just feel the engine going flat and revving no higher. Fuel-injected systems do it by interrupting the injectors, but a carbureted engine doesn't have that option.
Hmm,you may have come up with my next project!I do have a pulse generator and a O'scope.I'm thinking a square wave for the pulse.
I guess if you put the CDI input on Ch.1,and the output on Ch.2,it would more or less show the advance curve and how it behaves as the revs go up.
The Savage fires twice per revolution,doesn't it?
As an aside,I have a '91 Suzuki Bandit(carbureted)that definitely does use the cut-off type of limiter.Breaks up really well at 13,500 RPMs!
Of course,you did say CURRENT EPA regs,so that doesn't say much.