Planet Minis

50minikid

I bought this z50 a while back for $75. I have decided to fix it up and ride it abound the house. My question is on the motor can I replace the cylinder, piston, gaskets and other parts with parts from a newer xr50 motor on it? Thanks and I will have more questions as I go along.

50minikid

someone has to know, also what is a good way to get the tank good enough to use. I have heard kreem works but can flake off into the carb.
Thanks

arlindsay1992

No you can't use a CRF50 top end. The connecting rod is longer on a CRF50 so the parts for it are made differently. If you installed them on your bike you would lose compression and power. You can't just swap the cranks because the taper for the flywheel is different. But DrATV sells bolt up kits for your bike.

To get the tank clean, there is a process called Electrolysis. Here is a link to the process. There are a lot of threads on it in this forum and the ZB forum.

650 Rider > > Content > > How to Documents > > Removing rust from fuel tanks and parts with electrolysis

Here are some kits from DrATV that will bolt up to your bike.

This kit is 88 and will bolt up. Uses an aluminum cylinder and is probably the lightest. Looks like there is no displacement marking.
88cc_CYLINDER_KIT C70_1970_to_1981 Z50'S_69_TO_81

Here is an 85 kit. Marked 49 with a steel cylinder.
DrATV OPERATES HERE

Or you can buy both of these and a gasket kit and have a 72 motor.
47MM_BORE (63MM/SHORT) STEEL_CYLINDER (MARKED_"72cc'') OR (MARKED_"49CC")
47MM_PISTON_KIT (OLD_50_DOME) OR (NEW_70_DOME) (SHORT_ROD) (SHORT_CYLINDER) (100020)

50minikid

Are the gaskets the same for both?
Also I have a bit of an oil leak coming from the shift shaft. I think there is a gasket there that needs to be replaced but my question is, do I have to crack to cases to replace this?

arlindsay1992

Shift shaft needs a seal to stop the leak. The gaskets are different for all the kits I listed. The top two come with gaskets. Only the bottom one needs a gasket kit and you need a 47mm head gasket.

50minikid

sorry I ment will the newer gaskets work on my bike? Do you have to crack the cases to replace the seal? If I do the Electrolysis do a have to seal it or something after it? Thanks for all your help.

arlindsay1992

1. The gasket kits come with parts for many years so you will get everything you need and some things you don't. The parts you use may not be needed for someone else but they will need parts you don't use. So it's one kit serves all basically.

2. No. Just carefully use a drill and thread in a drywall screw about 1/4 inch. It will pierce the metal frame of the seal and hold it tight enough to pull out the seal. Make sure the oil is drained or the bike is laying on the right side so oil doesn't come out when you remove the seal. Once you pull the seal out tightly cover the splines with one layer of electrical tape so they don't cut the new seal and put a tiny bit of oil on the tape and shaft. (see first picture.) Slide on the new seal and push it in until it stops. (see second picture.)

3. Not necessarily. But I would. Chances are it will flash rust as soon as electrolysis is done so you would be better off to seal it. I know I would.

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50minikid

Thanks a ton for all your help, what sealer would you use?

mexicanyella

The old-fashioned way to deal with internal tank corrosion crap is to put some handfuls of nuts and bolts, or small gravel, in the tank along with some kerosene or diesel fuel, and shake, rattle and roll that thing as long as you can stand it. Then put it down, do something else and come back later and shake, rattle and roll it some more.

Antique tractor restorers joke about this being a great way to involve children in an old tractor resto project--"yeah, you're doin great, keep shakin that thing awhile longer".

The hard objects with corners that you put in there will eventually knock all the loose crap off, then you empty it all out, flush it clean a couple times and run a inline fuel filter, and expect to clean it and replace it often for awhile. But it works, if you go after it with some patience.

arlindsay1992

Do you mean seals? I just use OEM ones from DrATV. You can get kits from eBay also. I bought one but wasn't happy with the countershaft seal. I always go OEM now for the seals.

50minikid

I am putting the engine back together and am having some problems with the cam alignment. What position does it go. The first time I had it together you would rotate the flywheel and then it would stop. Thanks for all your help.

50minikid

here is a pic of how the cam is now. What way do I have to rotate it?

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arlindsay1992

Rotate the came until the red line lines up with the notch in the head at the green line. Then adjust the cam chain until the circle in the sprocket lines up with the the green line when the flywheel is at TDC.

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50minikid

Thanks that helps alot, sorry for all the noob questions.

cdoublejj

looks like yours doesn't have the notch either, my s65 engine is the same way.

arlindsay1992

You can't see it in his picture because the gasket is still stuck on there.

50minikid

Yeah it has the notch, I fugured out my problem, I was using a crf50 head gasket which was way to small bore. Stupid me.

69z72r

that thing kinda reminds me of a rat bike. haha. that would be a cool look and then put a straight pipe on it

50minikid

Yeah, I have the bike apart and am working on it, will look alot better when done.

1984z50r

that bike looked cool just the way it was