Running the TZ350 close ratio gearbox in the RD350 engine without a cush drive made us a bit nervous. As the NC30/35 swinging arm hub doesn't incorporate any kind of cush drive, a solution was needed. The goal was to be able to use standard sprockets so that sprocket replacement and gearing changes would be straight forward using off-the-shelf parts. We looked into using a Triumph and VFR800 style cush drive, but didn't like the bulk of it. Plus, it wasn't going to be a straight bolt-on conversion either. So, after a bit of thinking, we decided to produce a new part, a "spider" that would hold six cush drive rubbers and bolt onto a revised standard NC30/35 sprocket carrier.
We finally got around to fitting the rear subframe. Although the standard YZF-R125 subframe is on the heavy side, using the rear part of an original frame is much easier than trying to build a subframe from scratch. It would be a massive amount of work to duplicate all the mounting points for the tail panels, seat, pillon pegs, etc. So, using a written-off frame, we cut off the rear section and welded on lugs to bolt onto the TZR frame. This was actually pretty straighforward, just 4 bolts, really. Here is what it looks like with the seat panels fitted.
This project has been lingering for a long while now due to a busy workshop schedule. We really wanted to get out on it this summer. But, even the best plans sometimes get interrupted by reality.
The engine has been completely rebuilt, both cosmetically and mechanically. The main reason for re-doing the engine was to strip the cases and cylinders of paint and have them vapour-blasted for that bare aluminium look. It was quite a bit of work, though. The other reason was to measure all of the engine parameters, such as port dimensions, timing, etc., in order to model this engine and design the expansion chambers and inlet tracts based on detailed engine simulation. This approach has been so successful on the 95Racer project.
Well, now that the 95Racer is in a more or less finished state, which is hard to believe in itself, it was time for a new diversion. This project is very much a personal project and as such will replace some fairly arbitrary choices and decisions. So, having thought about this for some time, this next project will be a road bike. A 2-stroke no less! In brief, it will consist of:
- Yamaha TZR 3MA frame
- Yamaha RD350 Powervalve engine (somewhat modified)
- Honda NC35 single sided swinging arm
- Supersport front-end
- Yamaha TZR125 tank
- Modern bodywork
How did we arrive at this combination? Well, there was this RGV250 with a bit of a special RD350 YPVS engine that had been gathering dust in the back of the workshop for some time. This is what it looked like in its neglected state.