Disassemble a Puch ZA50 Engine
From Moped Wiki
Video 1 Disassembly with factory Puch tools.
Video 2 Disassembly without factory Puch tools.
Video 3 A quick tear down of the second speed drive gear and some talk about the shift dampeners (pucks).
Refer to the manual for torque specs and factory shimming process. Credit goes to IRE Tom for pictures and text, PHILIP PATRIE for shim guide, and dgrubers for wiki write up.
Tools you will need for disassembly
- phillips head screwdriver
- socket wrench
- 8mm or 10mm socket (1/4 inch drive)
- 15mm socket
- 24mm or 15/16ths socket
- needle nose pliers
- rubber mallet
- piston stop/rope/magneto holder
- impact driver (optional)
Remove transmission bolts
Take the six bolts out of the transmission cover. If bolts are tight, consider using an impact screwdriver. Also consider replacing them with hex bolts. Use a rubber mallet to get the cover off, and take care to keep the gasket from tearing.
- (2) M6x70 din964
- (4) M6x55 din964
Remove 1st gear nut
Wedge a 8mm (some use 10mm) 1/4” drive socket between the main drive gear and the case – or the “second gear lock” if you happen to be one of the lucky ones with dealer tools.
Use a 15mm socket to loosen the first gear nut. This is reverse threaded (rightie-loosie). If you just loosen the nut and not completely free it you can remove the first gear without having the bearings fall all over your shop. From factory this is very tight, consider using a breaker bar; mine was so tight I needed to use a pneumatic impact driver for about 30s.
When you pull the gear off, look out for a washer on the underside, which sometimes sticks to it. You'll see this in paz's video.
Remove the clutch bell to reveal the first speed clutch. Flatten the lockwasher and use a 24mm (15/16th”) to break the clutches free. For this you need a piston stop (the rope trick), or the factory magneto stop tool.
Remove first gear, cone washer and second gear.
Then remove second speed drive gear. There is a shim on the cover facing side of the second drive gear, dont lose it! (same washer/shim as mentioned briefly above)
Almost naked case!
Then using special tool #900.55.austria (read: needle nose pilers) undo the return spring for the starting mechanism
Remove circlip from inside of cltuch starting pad. Remove shim, spring, and clutch starting pad.
Totally naked case!
Parts in order
All the parts in order. Crank Side:
Time for Pucks, I didn’t grab a photograph of the second gear, but there is a plate on both sides, the back side has 3 flatheads (maybe we can get allenkeys?) There are lock-tited on from the factory, some people use an impact wrench, but I just used brute force. This is what it looks like with the back plate removed:
You have three main choices for replacement pucks.
- Paz pucks
- Motion Left pucks
- Atomic pucks
Installing the pucks can be a bit of a pain in the ass, but don’t mar them or anything like that, they all fit, its just a little tight. When you finish replace them, make sure to use blue locktight on the three screws that hold the puck plates together on the second drive gear. The screws have no specified torque; try to make them flush without stripping.
Reattach Return Spring
This is kind of a pain in the ass
Starting mechanisms all finished
Second gear clutch
Second gear clutch side gets thrown on:
Second drive gear
Second speed clutch
Consider flipping for later engage time. (Triangle faces down towards the starting mechanism when it has been flipped, or up towards the transmission case cover if stock). Definitely measure your float and reshim if you do this, then again, do it even if you dont.
Cone shim between 2nd and 1st speed clutches (make sure the cone side goes towards the 2nd speed clutch!!)
First speed clutch
The first gear clutch is flipped in the following photograph. The triangle on the clutch should be facing inward toward the case.
The lockwasher goes on so that the cutaways “wrap around” the chain links in the first speed, like so
Clutch retaining nut, 2 speed . . . . . 21-24 ft/lb (30-40 Nm)
Bend lockwasher around flat of a nut.
First speed gear
The clutch bell is not installed in the following photographs. You must install the clutch bell before completing the following steps.
Reverse threaded roller bearing nut funny thing
Roller retaining, left hand thread, 2 speed . . . . . 25-36 ft/lb (35-50 Nm)
Roller Bearings—also kind of a pain in the ass, these are inserted “against spring tension”—i used needle nose pliers to hold the bearings and a small screwdriver to push the spring back.
Crazy cap for the gears. This is also helpful for shimming, if you can do that.
Clutch case screws . . . . . 6 ft/lbs (8 Nm)
Rebuilt ZA50 Transmission, now, go drink a beer and be happy with yourself.
Since my ZA50 refused to roll backwards, that was nice enough to allow me to realize it was shimmed incorrectly. I have not the factory tools to measure, and even though they work very well, it isn't really a measurement so much as it is like a mechanical version of putting your fingers apart from each other on the back of a frame you want to hang up, and then moving them to the wall to make pencil marks. So with the advice of Mr. Mike Mike Naz, I went and purchased myself a machienst square, which was about $12, and a new battery for the shops digital calipers, which was $6. Oddly enough. So using the straigt edge, I was able to accurately measure the distance from the case, including the gasket, to the inner bearing race, as seen here.
Credit goes to Dean, who had to take this picture twice as the first time I was incorrectly measuring the other bearing by mistake. Then using the straight edge, it gets a little trickier to measure the gear of the bellhousing, but not too difficult once you get the hang of it. Take several measurements until you can get a consistant reading.
Take the two readings, subtract the bellhousing from the case measurement, and you have your end play float. Mine was .6mm with no shims. The factory specs are .05 - .25mm, which is as Chuck suggested, about the thickness of a Dr. Pepper can. Since I want to stay away from aluminum in this engine. The shim that I had in there was .6mm, and to land right in the middle of the float range, I wanted a .3mm shim. Since there were no local places that I could think of that might cough up the shim, I attempted to sand my shim down .3mm. All I really did was end up sanding my finger tips off, at which point I gave up and used power tools, effectively ruining the shim. That's fine, McMastercarr has the exact shim I want in a box of 25 at .1mm thickness for only $5. So I can stack a few here and there to get the height correct and be happily riding doubles in no time. Naz also suggested that I remeasure the float after a few miles since the bushing he machined for me might settle in a bit. No problemo!