97 670 question

[JD TECH]

Hey guys,
I have a buddy that bought this sled, when he bought it, it had a Union Bay head on it. He went to put a stock head on it, and the pistons hit the head when he slowly rolls it over. My question is, what big bore kit was installed in this sled? Is this a Union Bay motor? The jugs are not billet.The electrical also looks like it has been changed coming out of the stator. Any help would be appreciated. Thanks

 

[DWHalverson]

Measure the bore or measure the head and if it is around 82mm, chances are it is a 740 big bore. Very common big bore for that engine and for Union Bay.

Dave

 

[DWHalverson]

I forgot to mention Ski-Doo had 2version of the 670. One had flat top pistons and one had domed pistons. This coyuld be what you are running into also.

Dave

 

[JD TECH]

thanks DW. I will measure the bore, he says he has domed pistons. The pistons were hitting on the outer edge of the dome of the head. I don't know much about doo's, so i didn't know what bigbores were out there. Is this a good engine if that is what he has, or should he dump it and run like a lot of other big bores out there?

 

[winter brew]

If it is a UBR 740, that is a good, solid engine and should run with good running 800's of today.