Kawi2strokes.com Forum

This is the area of the failure on the seal I saw. The cross section of material was only about .010in between the bottom of the first lab groove (in the ID) and the 90 degree intersection on the OD of the seal's extension. As such any sort of rub will shear the resulting ring(s) off. However, the main body of the seal must be cut back somewhat to allow oil to the side of the adjacent bearing.

It must also be remembered the cranks on our triples definitely whip at various speeds, so the crank could hit the ID of a seal if the seal's clearance was too tight. The same whip is responsible for the CDI pickup being clobbered by the signal rotor if its gap is too tight.

J

So if you had a lab seal crank that was fresh but didn't have the o-rings you would check....
OD of the lab seal the same as the bearings, check the case for correct size with a bore gauge?
The more I read the more I prefer rubber seals. I can see how the lab seal would be great when
everything is correct and spot on. But with cases being 40+ years old how many are good enough
for lab seals.

Whatever you are comfortable with. There are probably 100's of triples running around with lab seals, not to mention 1000's of 40 year old RDs with them. The jury is still out on the ethanol issue and rubber seals.

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

The easiest way to find out if a rubber derived part is compatible with any fuel fluid, is to drop it into a bit of the fuel fluid, and let it sit a full day.

The part itself will tell you if it will live, or die in that fuel.

That might work if the gas companies were consistent with their Ethanol content, but they aren't. Our pump used to say 10% max ethanol, now they just say ethanol enhanced. And I know it's more than 10% now.

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

The new EPA ethanol spec will be 15% (some areas of the nation now have this specification in place and operating). It doesn't matter the concentration at this point, only IF the seal will stand the ethanol, at any percentage of concentration. As little as 2% can adversely effect some rubber derived compounds.

What ever percentage of ethanol anyone now has to contend with, doing the fluid test should give a suitable result as to go/no go for the compatibility.

All the more common sense reasoning to go to aluminum center seals.

Reviving an old thread, I hope someone is listening.

I'm about to get my crank rebuilt and am considering lab seals. Based on the thread I'll definitely mic the bore and seals to see how they fit.

As to the clearance, is this set by the crank builder or is it set when you bolt the cases together? Do you place the crank in one half of the case, adjust the clearance, and then bolt it all together?

Lot's to learn.

Dave C.

The clearance is set by the person who makes the seals. A good crank builder knows exactly what's needed.

Charlie Smith in Baltimore did mine. He can supply seals of the correct dimensions. He says to put a tiny bit of a particular Loctite on the seals when installing. His price for seals is very fair. Direct any questions to him directly and I'm sure he'll give you good answers. He's in the vendors section of the resource site.

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If it surges, that's normal, upshift.

Jim, thanks for the info. I have a pretty good rebuilder in line to do the job. I'm going to make I ask him about it beforehand.

Dave

One very important factor is the integrity of the crankshaft straight. ANY misalignment would cause a seal race to orbit, not spin concentric, so, get them cranks dead zero (YES, Hurley and I used to have contests to see whom of us could get the most "dead on straight" cranks done. Get 'em dead straight, men!

Now, a misnomer has been going on for decades about H and S series center seals. ALL OF THEM, ALUMINUM, AND STOCK RUBBER, ARE A LABYRINTH DESIGN. They all have internal sealing lips, more than one, and are not designed anything like end seals.

Of the earliest rubber seals, they used crankcase pressure to push the lips onto the seal races, later ones were positive contact.

So, when you say "Labyrinth", please be so kind as to specify if stock rubber early, stock rubber late, or aftermarket aluminum.