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Discussion Starter #1
I'm doing the top end on a z50 k6. Naturally, I didn't take notes when I disassembled the cylinder and head. Now I can't remember the placement for the o-rings between the cyl and case, and head and cylinder. I know where the centering pins go, only because they are still stuck in the case and cylinder.......just not the gaskets.



Is there a thread/link on this? Nothing helpful (diagram) came up with search function. Any help is appreciated.



Also, another question: When replacing the guides and rollers for the cams, I noticed that my kit had the lower guide (with metal teeth); however, I don't see how that can be replaced without splitting the cases. Am I missing something?



Thanks :confused:
 

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Discussion Starter #2
Re: FIGURED IT OUT...cylinder o-rings

Just an update - I found instructions for an 88cc install that highlights the o-rings and gaskets. My only concern now is that none of my o-rings are green.... I remember from my last build that there was a green one that slips over a stud.... I guess I'll just judge by the size?
 

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This isn't the 44mm bore one you mentioned, is it?



That toothed guide...you mean the oil pump drive sprocket? If it needs replacing, it unscrews from the oil pump drive shaft. I've never tried to remove one on an engine that wasn't mostly disassembled. Hmmm. Time to experiment!
 

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Discussion Starter #5
Tmas - Thanks for that link!



Mex - this is for a 72cc cylinder on a z50 case...to be used with the z50 head. Just for a little more "umph". That mystery engine with the 63mm stamp, I'm not messing with it since it loves to run.



You are right about the oil pump drive sprocket. I've only done top ends and timing chains on a couple of these and I guess I never had a timing chain "kit" that included the pump sprocket. I sat there looking at it for at least ten minutes. Once I saw the threads inside, I realized that it is meant to be replaced when you have a complete case splitting teardown....unless someone comes up with a neat trick. If someone didn't already spot weld the kick onto the shaft, I would contemplate pulling the oil pump to see the shaft could be held from that side, and then spin the sprocket off. I'm not going to worry about it - the original looks fine and I hereby declare that this motor isn't intended to be around for another 35 years.



BTW - I went to put the rings on the new piston and I snapped the oil ring in the process. This piston and ring setup is different for me in that instead of having the wavy ring sandwiched by two other rings, its all one piece with absolutely zero flex. SSSNAP. I'm not the most experienced so I need to look around youtube to see how this is done.
 

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Discussion Starter #7
I don't readily know anyone with a shop or ring expander but could find someone. I didn't have any problem with the stock 50cc piston rings in the past, but like I said, the oil ring was three pieces - flat/wavy/flat and seemed easier to guide onto the piston. This one piece ring seemed very fragile. I'm guessing it has more to do with my lack of techinique.
 
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