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1978 Yamaha IT175 Top End Rebuild

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Hello all,

I recently picked up a 1978 Yamaha IT175 off of Craigslist that needed a ring. Instead of doing just the ring, I have ordered a new piston and ring and am going to replace both. 

I have never worked on a 2 stroke this old before and have never done a top end on any bike before, so I was wondering if anyone could put me in the direction of an instruction sheet for the top end on this bike as well as some tip and tricks for general stuff. Also, if anyone has first hand experience with a similar bike, that would be awesome!

Thank you all in advance!

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Did you inspect and measure the cylinder before ordering new parts ?

(before the advent of Nikasil plating, it was common to rebore/oversize cylinders back then)

Actually I'd wait until seeing if there's play in the crankshaft/rod bearings before ordering any new top end parts.

Edited by mlatour

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I have not had a chance to open it up and measure it yet, but the guy I bought it off of said it has never been rebuilt or resized, so the piston and rings would be stock bore. 

I am fairly confident that it is the top end rather than the crank/rod bearing as I have done quite a bit of research to come to that conclusion, however I will check for play in the bearing. If there is play, what should my next step be?

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I'm doing my first ever rebuild on my '78 yz400. I've got a thread going if you want to follow that. Currently waiting on parts. Then going to get it bored. It's pretty easy to do. Just make sure you've got some basic tools. Mine is still running stock bore as well. You can check your crank, it's pretty easy. Once you pull the piston off just grab the connecting rod with your hand. If you feel any up and down play, you've got a problem. There is supposed to be a little side to side play, max 2 mm. That's how the manual says to do it.

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