787 crank bearing oring size & material?

[CASPX]

Finally getting 787 motor back together on rebuild and noticed crank rebuilder missed a crank bearing oring on one of the center crank bearings.

Checked parts fiche but didn't see any info so....

Couple questions:
1) What size is this oring?

2) What material is best for this application? Is vitton better than stock/standard/silicone?

3) is it possible to put the oring on the inside bearing over the crank web without stretching it so far out it doesn't fit correctly?

Thanks

 

[CASPX]

I heard it's a 2mm by 67mm vitton, any truth to this rumor?

2) is it possible to put the oring on the inside bearing over the crank web without stretching it so far out it doesn't fit correctly?

 

[howie099]

take the crank back to have them fix it.

 

[mikidymac]

I don't think the o-ring will survive being pulled over the crank webs and rod. I would have the shop that did it fix their mistake.

 

[Shortrun]

What is the job of that o ring?

 

[CASPX]

Ok, found a local place that has the oring, ordered & confirmed that the oring is vitton with 2mm thickness by 67mm Inside diameter.

Since I have a couple on the way I decided to take the chance and move on of the outer ones to the inside and after a little finagling I got it over the crank & webs and in to place without damaging it.

All I need to do is wait for the new ones to arrive and put it on the outside bearing

What is the job of that o ring?

It replaces the indexing pins so the bearings won't spin

 

[racerxxx]

Well you're partially right. The pin actually replaced the o-ring, years ago

 

[Shortrun]

Thanks for clearing this up for me.
So the oring could be cut and installed with a gap?

 

[racerxxx]

No, the o-ring is the retainer and keeps the beating from spinning in the case and destroying the case. Ski doo originally did that, then Seadoo carried it over, then they changed to the pin which is a better design. Crank builders buy the o-ring grove bearings because they're a standard being with that groove. Personally I'm not a fan of that on a high horse power engine, but it's perfectly acceptable in lower hp engines. The o, rings trend to cheese out after the first install