za50 trouble shooting

So I'm going to help my brother work on this problematic za50 that he has been working on for a while. I wasn't there for the building but I've heard and had him describe a few of the problems. I've never worked on a za50 before so I figured I would shoot some of these out here.

magnum has new 70cc kit and exhaust, treats cdi, daves phbg knockoff carb,

the inside is still pretty stock.


1. bike can start, i guess now sometimes you have to hold the clutch for it to stay running? did he put together clutch assembly wrong?

2. When the bike was running ( when he was trying to jet/adjust timing), the engine sounded like it was very clanky and unusually noisy. piston slap? something loose inside?

and 3. The bike has been on the verge of running. when trying to jet and everything else before, the lowend was just real sluggish. just kind of slow overall, so any ideas on what is missing or wrong?

Again I know these are general things, but I'd figured I'd ask just in case there were za50 specific things I needed to know about.

Re: za50 trouble shooting

Sounds like once you get that tuned it'll be a beast.

Sounds to me like the CDI wasn't installed correctly... maybe the jetting too... If the small end bushing is ok, then I say the CDI isn't adjusted right. You said low end was sluggish, but what about the top end?

BTW with that setup... if you haven't replaced the pucks... you risk shredding them easily and wreaking havoc inside your tranny. Gear shear, bearing failure, general FAILURE... You should replace with that power house :P

Re: za50 trouble shooting

yeah that's what I was thinking, I haven't toyed with it much, my brother did the rebuild and doesn't have time to finish now i have to do it. That's why I asked general questions to see if there were any za50 specific things I didn't know

pucks? that may be new to me? more info?

Re: za50 trouble shooting

You say "rebuild". But is it an actual rebuild with seals/bearings etc? Or does rebuild just involve throwing on the kit, etc?

Re: za50 trouble shooting

entire case was opened, seals and bearings looked to be in good shape

Re: za50 trouble shooting

The only reason I say the timing is because of personal experience riding a bike with WAY screwed up timing. It just seems like what I would have described. Of course it could be something else. If I understand correctly the only difference between CDI and points is that points wears out and CDI doesn't, but if not used correctly CDI can still be out of time. As for the pucks... if you have upped the displacement, got a new pipe and maybe a new airfilter, running the original pucks is risky. That's a lot of power going through the transmission. Anytime I see someone on here with a ZA50 I ask them if they have replaced their pucks. They are in the second speed gear and absorb the shock of the second speed clutch engaging. I didn't replace mine, and they disintegrated causing my tranny to seize and three bearings to fail.

Look at these two pages since you already have it apart.

You can buy new pucks here:

Re: za50 trouble shooting

sorry, new pucks here:

BTW... is there play in the piston wrist pin when it is in the connecting rod?

Re: za50 trouble shooting

ok... thing is messed up..

btw... is there play in the piston wrist pin when it is in the rod?

Re: za50 trouble shooting

I'm gonna get to it on monday. ped has new pipe, carb, and malossi filter. didn't really know about the pucks (I'm used to e50 not the za50). I'm gonna go through thouse videos and wiki.

I told him I thought the timing was off as well to begin with, but now I think it is a good idea to replace the pucks.

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