MZ/MuZ Riders

Reminds me of car rear differential gear matching..

Did you try different positions on the splines? IE; when it gets to the tight spot, mark the relative position to the splines then try one of the other positions.

Is it a reproduction or an original spare part ?
Some reproductions had the problem that they were not drilled exactly in the middle. So the distance varied and it could not be turned properly...

Not rotating around the centre - that would explain it. You should be able to measure that.

Thanks for the input guys. I reasonable sure it was a genuine part , anyway I have now replaced the driving wheel/ clutch centre with a new one, torqued the nut on the big gear down and the gears now rotate in harmony. So I think the issue was old trying to mesh with new. Reminiscent of my first marriage ,my wife was 13 years younger than me , we though that we fitted each other but could not function without clashing.

Progress has slowed up a bit as I ride the roller coaster of life.

I have managed to squeeze in a little ETZ time every now and then. I have lapped my old clutch on to the shinny new crankshaft , carefully cleaned off the surfaces and torqued the clutch to 90 Nms , crossed fingers that I dont have the same problem as @skyeport; I hope to get the clutch cover on the engine this week end.

I ordered a replacement stand bumper which I was intrigued to find it made of bakelite. Quaint but not entirely functional in my opinion. Unfortunately it shattered as I tried to install it. So I have opted for a block of seasoned Australian hardwood



The latest issue is fitting the rear wheel. When I finally fitted the cush drive around the right way and fitted the brake hub I find that I there is not enough space to fit the side stand or the spacer that replaces it ( by a good 6mm). The wheel hub is original but I have replaced all the missing parts, brake hube , shoes, cam, cush drive and sprocket hub, axel and sidestand

Remembering that the rear wheel was not in the bike when i got it, I wondered if the ends of the swing arm could have been bent inwards at some stage. I measures 220mm between the swing arms at the chain adjusters.

I have about 21.5cm between the arms of my 251, with the wheel mounted.

I can't wait to find out the cause of this missing 6mm of clearance. I have never had the sprocket and cush drive off my ETZ250 but no doubt, one day I will need to, so it would be nice to be forewarned.

I'm pretty sure its an assembly issue. I put the parts in place without the chain guard and it all seems to fit better. So maybe the speedo drive not meshing properly. Unfortunately I have had no opportunity to do any serious work on the bike since getting back from the desert, really just a few minutes here and there.

I don't believe the chainguard in itself, should take any load. It is a plastic (type).

I might perhaps look at the chain guard miniature spindle (?) and also check bearings had been pressed into the hub properly.. I believe there's two in the chain hub.

progress with the engine: fitted piston and cylinder

Puffs wrote:I normally try to keep an engine light to ease hanging it into the frame, but heavy works too. And that looks like a Vape rotor.

Out of interest: did you do a re-bore? What piston did you choose?
Currently I'm having mine rebored and I went for a 70.95mm Almot with 0.05 - 0.06mm clearance. Time will tell if that's a good choice.

Yep , Bruce also warned me about keeping it light for remounting. The frame is still tucked away in a hard to get at space in my garage until I can reassemble the rear wheel and move it to a postion where I have room to mount the engine.

I went 69.5 which I think is 1st oversize.

I purchased the power dynamo VAPE as my generator /ignition system was buggered.

Next piece of the puzzle:

All of this was missing when I got the bike


Im guessing that the activator goes together something like this
.....