I had set myself the goal of building a high-torque, high-displacement everyday engine. Initially, a defective first generation ZT100N was to be fitted with a cast iron liner. This plan was discarded when I was able to get hold of an old Yamaha cylinder on the internet at a reasonable price. This comes from a Yamaha RS100 (was built 1976 to 1981).
Based on the cylinder I built an engine with about 110ccm (48mm stroke x 54mm bore). Due to the choice of the cylinder, a relatively complex adaptation of the Simson engine housing was necessary, which involved material application by welding and offsetting the stud bolt holes and widening the housing bore to 62mm.
From left: Adjusted, blasted housing; Finished assembled hull; Comparison to ETZ 150 cylinder
Initially, a standard long 5-speed gearbox was to be fitted in the engine, which was to be equipped with a second gear from RZT and a sensible pulling wedge. However, the new ZT-Tuning 5 speed gearbox appeared reinforced version 2019 (middle 1st gear), which I liked right away and made some adjustment work unnecessary. In addition, there was the price, which is on balance cheaper than a "self-assembly".
After receiving the transmission, it was completely disassembled and checked for dimensional accuracy. The bearing seats are all precision machined, as are the gears and the thrust washers in between. One of the thrust washers was manually deburred, because there was a sharp edge (from laser cutting). The gearbox was also equipped with balls from Kugelwinnie. This would not necessarily have been necessary, since the supplied balls had a similar hardness (jump height test on steel plate made for comparison). Have these only "for a clear conscience" built.
As for the shift operation, some improvements were made. First, a bolted shift drum bolt was installed, the axial play of the shift drum was brought to near zero and the shift drum itself also still needle bearing. In my opinion, the main problem for the partly poor adjustability of the transmission (as with all 5-speed transmissions) is the shift drum. The cam track in the roller measures approx. 8.15mm, instead of 7.65mm as with original DDR rollers. This leads to a dramatic increase in the play of the swivel arm in the cam track. As a result, the angle of twist of the roller per "shift lever stroke" is not sufficient to push or pull the draw wedge into the next gear. Many then start filing the stop on the shift dog to get more travel. Since I didn't want to do that, the pivot on the rocker arm was turned down to 5.05mm and with the help of Loctite shaft-hub a hardened sleeve with 8.00mm outer diameter was pressed on, which brought the clearance to the cam track back to a minimum. This allowed a good and fast adjustability and a precise and crisp shifting gearbox was the result.
To ensure the durability of the transmission or minimize the chances of defects, a double-row clutch shaft bearing was installed in conjunction with a straight-toothed primary drive from Ronge Motorsport (18:53). At the rear wheel, the shock absorber was also converted to the Ronge system.
Currently, the gearbox has almost 600km on the hump and there have been no abnormalities so far. Within the 600km, among other things, participated in the Harzringtreffen, where the engine was also not spared on the track.
Finally, I would like to talk about the performance values that the engine delivers. These can also be safely guaranteed, since, as it unfortunately turned out afterwards, the armature plate grinded on the hub and thus higher losses than actually existed. The problem has been fixed in the meantime, but I haven't had the chance to make another comparison measurement on the P4 since then.
Red: AOA4; Blue: JW Factory 1; Green: JW Fat Lady 3, Turquoise: JW ST 85
ZT Getriebe Einstellbarkeit
Schöner Beitrag!
Genau das kann ich auch bestätigen, habe alles versucht das Spiel der Schaltwalze und der Hebel so gering wie möglich zu halten, um eine einigermaßen gute Einstellbarkeit des Getriebes zu gewährleisten.