Hi gang, well I'm a heavy rider, and have been doing this for a long time. At first, there were only WhizzerUSA and the Chinese 2-stroke from Angelwings which was Steve Miller's company selling under the brand name SpitFire.
I bought 14 of those and still have 2 of them (sold the rest, I never rode any single one long and hard enuf to blow it up). I then switched to Grube as a Distributor. I sold, repaired warrantied, and witnessed devastation with some of those engines for a long time. With the 2-stroke, the reduction inside the engine is usually not the problem, the engine itself blows up, or wears dramatically.
I can tell you this I LOVE my 4-strokes, and only get on a 2-stroke when I am repairing it for someone else! I should keep one running here for customer test rides, but I have been busy, and unmotivated to do that.
Gearbox reliability: here is where the rubber meets the road on the 4-stroke! The engines are built for a variety of tasks and are well-proven. The HS clone of Honda is VERY good, and many times will outrun the Honda (maybe the cam is a lil different?), and seems to have a very long life, tho no-one I know has owned and ridden one long enuf to either wear it out, or surpass 5,000 miles YET.
I did some work on and rode 3 of the RS35's on 2 different drive systems, and a GX35 on another system altogether and they are too small, under-torque and did not impress me for the heavy rider.
Drive systems: well here we go, Early hoot had a weak cold-rolled clutch bell that the shoes of the clutch would cut the bell into 2 pieces, mine lasted approximately 50 miles, it was fun, but it was a bust! NOW do know that the Hoot improved that feature using a hardened bell that lasts much longer BUT they have a bushing in the bell, and that rides directly on the crankshaft, wearing the crankshaft surface any time engine is running and the clutch is not fully locked. To me this is unacceptable!
Noise in the gearboxes: The one Staton that I built for a customer was quiet. Hoot's vary from a whine to a howl, as do the earlier Grube units (no longer produced?). In addition, there is a lot of discussion about how to lube the Chinese boxes, and since they are "seat of the pants" engineering, there was no real Factory answer as to what to put in them. In their defense, it is reported that one guy successfully rides a stage 2 Hoot, and several (more than a few?) successfully ride Grube gearboxes.
I have plenty of new Take-Off Hoot boxes for sale really cheap if anyone needs them. It would be of interest to you if Red66 and Houghmade gave their experiences with their bikes, as those are the two most prominent riders I'm aware of.
Enter the new age, EZ Motorbike with the Silent Power transmission, EZ Motorbike Q-matic, and Grube 4G drive. I know nothing except what I have read about the 4G so check Irish John's thread about it, seems like it might have some problems.
The EZ I do know, I rode prototype EZ for about 500 miles before I switched to a production Silent Power on my Honda. It works extremely well, and if you ever had a need to repair it, all parts are readily accessible. I intend to put another 100 or so miles on it at the Whiz-In Oct 10 2009. It is smooth, reliable, the drive system is so quiet that all you hear is the chain on the rear. The engine is better than it has a right to be, holding 8oz of oil in the crankcase, it is a lean-burn certified engine, as is the HS 50.
Q-matic: I have about 200 miles on mine now, and it is everything it is supposed to be, American Engineering, and the whole Reduction (Primary) is American made, built in USA! We use American clutch, in an American transmission plate with an American made cover, all Gears, Chains, Sprockets, belts, setscrews, keys, gizmo's, gadgets and widgets USA made, or purchased from USA sources and unwittingly imports! My Q-matic will be on the ride, with wifey behind the bars, looking for another 100 miles on it also!
Quenton has more miles on his Q-matic than I do, he can comment on his success separately.
For me the answer is simple, 4-stroke engine, as presented, is far superior in construction, and overall performance, tho it does cost more at the beginning, it will repay you with less maintenance (almost none on mine) less, to no parts vibrating loose all over the road, less noise, cleaner (in every way) no mixing, just pull in and fill up!
I vote 4-stroke every time, even tho there are more parts inside, they are well known, well presented, and will take care of them selves, and for a total bonus, the HS50 and the Honda GX50 will NEVER blow a head gasket, nor a base gasket, nor strip a head bolt, never carbon up a pipe, and they do not foul plugs (in my experience), these are common maintenance items on the 2-stroke that you will never deal with on your new 4-stroke.