1972 Z50 top end swap

[ldouble619]

Hello,

I have a sickly z50 that has 30psi compression (checked timing and adjusted the valves). So I decided to order some CT70 replacement parts. I got a cheap top end kit off eBay to try it out. Can't go wrong for 55$. Link below.

My question... I read a lot about short rod vs long (1982) and I'm not sure if I will need a new piston with the kit I bought??? Since it's coming with the matching head, maybe not?

Thanks!

https://m.ebay.com/itm/Cylinder-Hea...70-S65-70CC-/201731625343?txnId=1669277062010

 

[motodevo]

That kit suits the 82 onwards rod. It will fit however as the piston deck height from the gudgeon pin is 3mm less than the original piston, the piston will be 3mm further down the bore at TDC from where it should be.
Ultimately you will need a new piston. Probably your best cheapest/option would be a 70s ct70 piston, but i cant confirm whether a short rod ct70 piston will suit the new head as i suspect your new head has a smaller dome than a ct70 one. Someone with more experience will chime in.

 

[Gary]

Something is wrong with that fitment list- say it fits 69-74 ct's 65-69 s65 then it says 98-04 xr70's also

 

[OLD CT]

Cheap isn't always good, good isn't always cheap.