I have some excerpts from the thread. It was regarding grafting RD350 cylinders to an H1 bottom end. IIRC it was in the Yamaha forum and the guy was running an Egli frame. Here are some excerpts directly from the thread (courtesy m in sc):
Quote:
...Glad you like it. I used a bridgeport mill to cut out the studs, and remachine the crankcase mouths after welding. The 4.8mm stroke difference gives TZ750 timings without modifying the barrels. I machined 5mm of the base of each to get the piston height right - quite difficult to get in behind the inlet port casting. The beauty of this is that the 'blowdown time stays the same as for the RD350, and the reed valve should compensate for the 5 speed box....
....Mike Pettifer was at the Broadford Bonanza a few weeks ago. Was the MK3 500cc Suzuki you had, the one which Cornell Suzuki sponsored Horsman on? I was talking to him at Sandown in about 1978, and he showed me the difference in the works heads on that bike. I'm using Wiseco RZ350 pistons in the Yamaha barrels I've fitted to the Kawasaki. You have to be careful machining, but a bridgeport mill is magic. The only real problem is in porting up to the barrels, it's easy to break thru the casting on the drive side of the crankcases. I had to use devcon only once . The crankshaft was rebuilt with Yamaha RD250 rods, and labyrinth seals. That way I get to use the Yamaha little end bearings. Kawasaki rods will do the job, they're the same length, you just have to buy different needle roller bearings for the little end. If you try this there is 5mm to be machined off the base of the Yamaha barrels to get the heights right, and maintain the 'blowdown'. The difference in stroke from the Yamaha RD350 gives approx TZ750 timings.
The stroke of the H1 kawasaki is only 4.5mm longer than an RD350. It stands to reason that the ports can be lowered on the RD barrels to end up with decent timing for this motor, I've cut 5mm off the bottom of the barrels. The 'blowdown' time is unchanged fron the RD setup, which is pretty radical anyway. Considering the stroke difference the 'blowdown' should be sufficient. I've measured the transfer and exhaust timings, and they're pretty close to a TZ750. I'm not particularly worried about the exhaust port heights yet. It's all been a matter of careful measuring of barrel heights etc. Theoretically the motor should be good. I'm still playing around fitting exhaust stubs to the cylinders so I can fit chambers. I'll let you all know if it ends up successful, but so far it's looking really good. I've got a minor peoblem using the RD400 flanges, they foul the engine plates I've used to lift the motor in the frame. ( I had a problem getting the head angle right, and lining up the sprockets, so the gearbox sprocket had to be raised to get the chain right.) But so far arse beats class, and it's all working out. Glad you like the bike, and I hope it inspires a bit more enthusiasm in you, and you might try something similar some time. As soon as I've trimmed the engine plates, I'm getting chambers made. Got to fit the Krober, and gwet it working. I've bought a TZ750D fairing which looks great, just got to fit it around the motor and chambers.
Login
FAQ
