Reno,
I did a visual on the overlap on the noisey 6/1 and did a visual comparison on my other quiet 6/1 and they both appear to have the overlap. I need to drag my dial indicator over and do a real comparison. I have heard mention of folks dealing with the same issue so it looks like there is a issue that only causes the noise but doesn't bother the performance. Love to get rid of the noise without buying a new camshaft.
Dave
Heh, you should hear my ChangFa R185 !!!! It really honks when at speed. I removed the stock oil bath filter and intake pipe and fabricated my own setup to which I mounted a Solberg filter assembly/silencer made for air compressors. I think I used the 1-1/4 NPT size. It has a replaceable wire mesh reinforced polyester element with foam pre filter, and silencer tubes built into the assembly. It cut the intake noise significantly, eliminates the oil mess from the stock filter, and filters much better. It's a very nice unit.
Since I installed a big round NAPA muffler on it, the only noise the intake (still loud) and the mechanical noise (sounds like a rock crusher). But, she just chugs along hour after hour, sipping fuel, and keeping the lights on and the food cold when the power goes out.
I'd still love a Lister type, but just don't have the space for one.
Chris