ZA50 rebuild


I totally disassembled my ZA50 (new crankshaft from treat, new bearings, new seals)

After assembling the case, the crankshaft is rotating fine. As soon as I tighten the 5 screws (magneto side) and the 3 screws around the rear sprocket, tge crankshaft starts getting more and more tight.

I understand this might be a shimming issue since the new E20 and L17 bearings are not EXACTLY the same as the factory ones.. Or everything is normal, and the crankshaft is supposed to be hard to turn with my hands, and after a few miles, it'll get smoother..


Re: ZA50 rebuild

It should spin with ease and grace. No binding. You have some reading to do in the manual.

Did you remove the old races from the cases? If not, your going to have to do that.

Re: ZA50 rebuild

Michael Thomas /

And they can be a real bitch sometimes. Heat did not work for me the last time and I had to cut a slit in the old race with a dremel and chisel it out...not fun.

Re: ZA50 rebuild

I'm assuming you put new seals in, which will cause a little bit of stick but not so much you cant turn the crank by hand.

make sure your seals are pressed in properly, and that your bearings races and cup are pressed in evenly and completely.

As Ed said, new bearings must go with their new races/ cups

also, are you re-using or using new crankcase gasket?

it might also help to assemble the case halves in the orientation it would be when mounted to the bike...

there is a large amount of info on MA about this rebuild, you should be able to find your problem and solution on here by digging in some forum threads. bottom line, if it doesnt feel right, its not.

take it apart and do it again.

Re: ZA50 rebuild

Michael Thomas /

I kinda had the same problem on my last build. I used a double gasket on the cases, works perfect.

Re: ZA50 rebuild

Thanks a lot for the replies.

Yes, the gasket is new, I assembled it the ''right'' way like if it was mounted on the bike..

Everything is new actually, the cups, bearings...

I parted everything up, both cups looks fine in the case and so are the seals..

So I'm assuming I'd have to dremel the races? That's weird and it sucks.. Or double gasket..

Re: ZA50 rebuild

no. dont dremel anything, personally i wouldnt use double gaskets. the float on the crank is important and a double gasket will might throw off your shimming in the transmission.

are your races sticking up too far from the crank cheeks? then they need to be pressed in further. they should be nearly flush with the cheeks...

take out the bearing cups (heat case halves) and try to press them again. if i remember they should be flush in the case. nothing should stick out.

maybe measure your old ones with a micrometer and compare to new just to make sure its not a flaw with the new bearing sets?

Re: ZA50 rebuild

Probably Fred /

Sounds like the bearing set is not like original

Re: ZA50 rebuild

The races are fine I guess, Theyre further than ''flush'' with the case halves.

But I'll try to remove them and measure them...

My original case gasket looks fine, maybe it is 0,04mm thicker.. I can't imagine how 0,04mm can change anything when I tighten everything but the mystery of mopeds is far beyond from science.....

On treatland, they sell the 0,08 and 0,12mm case gasket. I thought it would make a difference with the and float only and couldn't affect the bearing binding as soon as I assemble the case halves.... I have the 0,08m gasket, maybe that's the problem.

Re: ZA50 rebuild

Probably Fred /

I don't know why but I like the thicker gasket

Re: ZA50 rebuild

Yeah, me too. I also like the cereal box gasket idea, or the liquid gasket... mhh

Re: ZA50 rebuild

Any guru knows somrthing about the tiny space between the crankshaft itself and the inner race. On the service manual, they states that there should be 0,20mm lesft side and 0,10mm right side.

I can't measure that exactly but I'm stating to think that the treats/77 za50 crankshaft are just not the same are the stock ones.

I'm gonna have have to sand that inner race until the binding stops...

the difference between the 0,08mm and 0,12mm gasket treatland sells looks useless to me now as it should only affect the end float and not the binding...

Re: ZA50 rebuild

meh, i put a .05 mm shim beneath each race, but i dont think it matters. that said i also used the teflon gasket on the crank case and i think that thickness is different than what you mentioned, but i cant recall my exact measurements

also you are probably right on the aftermarket cranks, do some forum searching I believe several MA za50 builders have commented in detail about where a certain cir clip sits in relations to some of the clutches.

Re: ZA50 rebuild

They are not the same as the stock crank. They are a little longer.I Believe they were made that way for a reason.I have a friend that has a za that has the 77 crank in it.He has been running hard for hundreds of miles without a shim on the crank side,and mabe one on the clutch side.If you sand it.Make sure you sand it even, and square.I would not sand it.

Re: ZA50 rebuild

That's why Puch made those fancy rebuild measurement tools. Even with a stock crank, measurements and complimentary swimming are necessary between the crank and one of the races.

Re: ZA50 rebuild

I think you're asking for worn out big end, small end, and damaged race surfaces by not shimming properly. You're letting your junk slide around all over the place and tweak everything up.

It doesn't matter what the shims are, so long as they come out to the right end play float.

And Joe the end float and the binding are the same thing... your crank is binding because you have no float. I'd personally go with a thicker gasket before sanding the inner race seat - that's just me. (edited)

Re: ZA50 rebuild

Also, it's possible to get the engine in the ball park end play float with calipers and a straight edge... I've done it plenty - though the tool makes it cake.

I'm still working on that za shim tool to sell on treats. I'm running a couple cheaper designs through the company I've chosen that have less critical measurements to test the waters with this company but it's still on my radar.

Re: ZA50 rebuild

I used normal printer paper(0,0038inch) or (0,1mm) PLUS my original gasket and that fixed the binding..(somehow)

Not ordering (treats) the 0,0012inch instead of the 0,008 was my first mistake...

My readings showed that my journey is not over, many circlip groves/shimming problems awaits.

I just hope that I won't need to shim the crankshaft (before the inners) and I guess not since my binding stopped for now...

Many thanks for all the replies.

Re: ZA50 rebuild

When people bitch about ZA's blowing up.... ^ this is why. Good luck - you're gonna need it.

Re: ZA50 rebuild




Chris Paz talks about the circlip groove that is 0,02' too far on the crank. That seems to be my problem. The solution to remove the washer after the circlip doesnt change anything since the second gear clutch goes 'over' the circlip and directly hits the starting plate, causing my problem : as soon as I tighten the clutch retaining nut, the clutchs engages, the rear sprocket is almost impossible to move and if it moves, it drags the crankshaft with it...

I tried to keep the shims on and remove the circlip. that fixed everything (for now)

Any one knows if that woud cause a problem?

The clutch retaining nut is torqued to like 30-40 nm, which is more than enough to 'push' that spring, instead of the tiny circlip..

I'm no pro , I'm sure I'm missing something big...

Re: ZA50 rebuild

Don't ever use liquid gasket on a ZA50 engine. These are the most unforegiving engines you have ever seen. The germans build them on a scale of presicion of the up most tolerances. So you need to Measure and Measure and remeasure. The snap ring is 1mm off as when they remade them at nice/rich factory they built. You'll need .1mm shims to correct the starter plate problem. You need to shim the output shaft outside.

Yes, you may have to use a .012 and .004 or 2 .008 to get the correct tolerances/play on the main crankshaft bearings. I only use the brands of sfk or fag bearings. Brand of bearings does matter imo as the design of the bearings have change... the thickness. You need to set the crankshaft to ZERO end play paz stated in one of his posts while back.

Here is some video about things that no one else addresses but me.

Re: ZA50 rebuild

I agree with everything mopagen has said - except zero play. It's not an accuracy... 0% error is great. However, there is a high and low side to the tolerance on the crank and transmission where above the high tolerance is bad and below the low tolerance is bad too.

It has to have SOME room to breathe

Re: ZA50 rebuild

thanks guys,

I understand that the shimming problem in the video is a common problem with all za50. It's not related to the new crankshaft, but important to know.

Almost all the threads I saw were talking about the end float.

I wish I knew before that I had to do compensate for the circlip groove, and also compensate for the lack of space between the starting plate and the second gear clutch.

Re: ZA50 rebuild

And again, it's not working..,2747740,page=2

In that thread, it explains clearly that the starter plate should be below. so the cone shim would rest on the shlouder on the crankshaft and not the clutch.

EVEN if I remove the washer after the circlip, there is STILL NOT ENOUGH space to clear that shoulder on the picture.

It's really a circlip groove issue and not fixable with shims.

The only way i find would be to grind a second circlip groove 1mm below the existing one. Is that doable without machine shops?

The other way wouldbe to litteraly grind 1mm off that 'highlighted' thing on the picture in page 1 of the thread.

I don't know how I'm can't find others posts with this problem since ALL the 77/treats crankshaft have this problem. Everyone talks about shims but it's not the solution here

Re: ZA50 rebuild

Make a video for us all to understand. That's just how easy it is. Then it will be easy to understand the problem. You'll need a lathe to machine the parts.

Re: ZA50 rebuild

Picture below.

What I call 'shoulder' is part on the crankshaft, exactly where the cone shim is supposed to rest.

The brass/metal piece is that thing that goes between the second gear clutch and second speed clutch.

The main problem is stated the the link in my previous post.

This is NOT a bearing/case/gasket/seal problem, I took the picture without the case.

Capture d’écran 2012-06-28 à 20.03.51.jpg

Re: ZA50 rebuild

Ok... i get it... you really suck at explaining things lol.

I don't know really how you're going to fix that without recutting that circlip groove on the crank.

If you lower the clutch any on the starter plate bell/second speed drive gear/second speed clutch mount plate - you're going to hit the second speed gear with the pucks in it.

If you drop the starter plate bell/second speed drive gear/second speed clutch mount plate any by grinding the surface that rides on the thrust washer that sits ontop of the circlip, you're going to engage the clutch.

If you recut the groove on the crank, you risk giving the starter plate bell/second speed drive gear/second speed clutch mount plate too much wiggle room and hitting the second speed gear with the pucks that drives the output shaft.

If you leave the circlip out completely, the clutch is going to hit the second speed drive gear with pucks that drives the output shaft or that spring is going to be a loose cannon and do who knows what.

Try assembling it without the circlip and one of the thrust washers... That's the only way I see it working without cutting a new groove. TBH, I wouldn't run anything like that.

I would try to come up with something else besides cutting a new groove, but I can't think of anything right now.

Sometimes the old stuff is the good stuff... Maybe you should just cut your losses and have your old crank rebuilt. You don't want to blow your shit up because it's jank.

I also hope you're not just trying to change the subject because you got your crank to stop binding... If that's jank too, you might as well just strap an M80 to this engine and save yourself the time and trouble. (edited)

Re: ZA50 rebuild

You could also try grinding the top of the starter plate bell/second speed drive gear/second speed clutch mount plate and second speed gear to lower it so that shoulder is exposed, but then you're decreasing the surface area of the second speed clutch splines.

Or, you could try and make an additional spacer that fits inside the starter clutch bushing to make a new shoulder for the cone to rest on.

My question is, if you stack your cone washer or whatever you're calling it - the spacer that goes between first and second clutch - on top of the second clutch, then first speed clutch, then lock tab and then thread the nut on without the nut going above the bottom of the brash bushing on the bottom of the crank... If you can't then you're going to need even more clearance and certainly not going to be able to come up with just a spacer.

I'd just chalk this up to experience and eat the $150 or however much the crank was and not ruin the rest of your motor and work.

Re: ZA50 rebuild

Haha yeah well I mostly speak french, that's why my english is weird...

I did change the subject because i fixed the binding problem.

My old crankshaft is not fixable, the magneto side thread is stripped big time and on the other side, the brass end bushing is bent due to hammering so yeah I just can't give up for now.. I can't live without my magnum

Re: ZA50 rebuild

You speak kick ass english for mostly french. Don't apologize lol

I'd try to find a ZA crank used to have it rebuilt. There's a parts motor on ebay right now.

The bushing can be sanded down, it really doesn't matter as long as the bell spins free but also not loose, and the threads can be tapped the next size down on the flywheel end, as long as it applies enough pressure it doesn't matter.

If you've got damage from hammering, it probably needs to be trued anyway, so have a new rod pressed in while you're at it.

Just a tip - a hammer is not a tool to be used on a crankshaft, unless you're trying to align it and have centerpoints and dial gauges.

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