Yamaha xs650 crank and rods Qs

Hey folks! I have a 1973 Yamaha TX650

Does anyone here know if the crank and head from my '73 (256 modal?), would work with the rod and piston from a '77 (447 modal).
It's my understanding that just the rod and piston was changed in '74 with the 447 modal engines.

I'm desperately trying to rebuild my old motor, and if I can do this with the rod and pistons from the '77, I can save myself some moneys instead of having to buy a new engine!

Thanks in advance for your knowledge!

Cheers!

Simply put, no. Aside from deck height etc. the piston pins are different sizes in the different motors, meaning the small ends of the rods are different on your 256 crank than on a 447 crank, so the later pistons simply won't fit.

Now, you can buy brand new pistons/rings for your engine from MikesXS. $87 each gets you a new piston, rings and pin in a 0.5mm over size, or 0.75 over (on sale in this size for $79). I've used MikesXS pistons myself.

http://www.mikesxs.net/products-25.html#product-05-0653

Or you can roll the dice a bit and for 1/2 the price buy a set off eBay from Japan

http://www.ebay.com/itm/70-73-YAMAHA-XS1-0-5mm-75-5mm-OVERSIZE-PISTON-SET-Two-Pistons-are-included-/130787069008?pt=Motorcycles_Parts_Accessories&hash=item1e73844c50&vxp=mtr

That's great info, I may have overlooked those pistons.

But perhaps I should clarify, I was planning on buying new pistons to go along with these newer rods that I'll be buy off an old '77 (447) parts bike . I thought about possibly buying the 750 kit they have on MikesXS, as long as the '77 rods work with my old '73 crank.

So as long as the big end of the rods fit on the old crank.. I should be fine? Does that sound right?