Mystery Motor - Yamaha 760

[JM113]

Hey guys....I have a Yamaha 760 engine that is a mystery to me.
The pistons stick up out of the cylinder approx. 4mm or so. Does this mean it is a stroker? It has an ADA Head with recessed domes.
62T cases and cylinder with porting. Have no clue what type of porting it has done but it looks really good!
Also I have no idea what the carbs are.....
So would love any help someone might be able to provide.
You can see pics in the for sale section: http://x-h2o.com/showthread.php?p=317186#post317186
Thanks!

 

[the only couch rider]

probably a 64X motor

 

[SuperJETT]

Hey guys....I have a Yamaha 760 engine that is a mystery to me.
The pistons stick up out of the cylinder approx. 4mm or so. Does this mean it is a stroker? It has an ADA Head with recessed domes.
62T cases and cylinder with porting. Have no clue what type of porting it has done but it looks really good!
Also I have no idea what the carbs are.....
So would love any help someone might be able to provide.
You can see pics in the for sale section: http://x-h2o.com/showthread.php?p=317186#post317186
Thanks!

You can have a stock stroke engine with pistons that come up out of the bores. I did. It's normally from someone wanting to lower the overall porting and report, so they deck the bottom. When that's done, you have to undercut the domes for proper squish/volume.

However, it could also be a 4mm stroker, the only way to know for sure is to measure the stroke.