First off let me say that this is a great site. Lots of great info!


Hopefully someone can help me out here.

I have a 1996 MXZ 670, I've owned it since 1997. I've never had to tear into the engine until tonight.
Went out on my first little ride of the season last night and could hear a winding noise from my clutch, well I was hopeing it was my clutch. Checked it out and ended up tearing the whole engine apart.

The bearing on the PTO side gave out. The bearring on the edge, next to the seal spun on the crank and wore the shaft 0.002"-0.003". Small metal particles have scored my cylinder and piston.

Can something be done to salvage my worn crank?

OR!!!

I have a older style 670, 93 or 94(the ones with the black head instead of purple) Are the crank, cylinders, pistons the same as my 96 670?


I don't want to tear apart the older 670 just to compare parts because it's a running engine.



Hope someone can help me out real quick so I can have my sled up and running before the weekend. :confused:

Can anyone tell me? I really need to know.

Well I made some phone calls today and I was told they are the same. Even though the crank case is very different(oil pump,water pump,supports)

I'm hoping a 670 expert can chime in and confirm what I was told today.

I'm planning on tearing the other engine apart Saturday.

i would pm thumbdoctor.

1993 ~1994 670 (type 669) crankshafts are not interchangeable with 1995 ~1999 models because the inside bearing races are narrower and flywheel key location. Take your spun crank to a machine shop and have it spray welded (Flash chromed) and reground back to stock diameter. If the damage is only .002" as measured, you can use Loctite 660 Quick Metal (press fit & worn shaft repair). You will need to order 2 new PTO bearings and a distance ring. The stock FAG bearings (BRP) with nylon bearing spacers do not tolerate too much PTO heat and fail. Atilier Adrien Bernard sells steel caged replacements for a reasonable price (he custom drills holes for anti rotation pins on the outer races). The main cause of your failure is a poorly engineered clutch kit (if installed) glazed belt and sliding primary sheaves. If your crank has anything else out of spec get an exchange unit from Bernard. Time to replace your primary clutch spring to as the heat that did in the bearings also weakened the primary spring.

http://www.cvtech-aab.com/DocumentsAtelech...ilebrequins.pdf (http://www.cvtech-aab.com/DocumentsAtelechager/2008/motoneige_vilebrequins.pdf)

Thanks for the input TD!

Your advice saved me from finding out the hard way.

Now I go back to try and salvage my worn crank. But the inner bearing on the PTO side(middle of crank) doesn't turn as smooth as the others on the mag side. My choises now are.:

1.I'll check what the cost is to split the crank and new bearings.
2.check for a rebuilt crank if it's not much more expensive.
3.Find a good running used 670.


Option 3 would make life easier. No boring out cylinders, new piston and rings, run iffy crank with loctite or buy rebuilt one.

I want to be ridding right now! Not stuck in the garage with grim all the way up to my elbows.


I've seen some of your post and now am wanting to port my engine and do the other mods later on when the snow is gone. But for now, I just want to ride.




Speeking of modding a 670. from what kind of sea-doo do you use the pistons from to make a 740? What would the part # be? Can I bore that big and still have a reliable trail machine? Can I run my stock carbs with 740cc's or should they be bored out as well?

Sorry for all the questions but reading up on some of the threads searching for 670 info, you have me real interested on modding my engine.

MXZ 740 sounds sweet!!!!! w00t




Again Thanks!
Peter