Recurring Crank Seal Failure

[Suzukidave]

I knew there was pressure feed oil getting in there but got my wires crossed where it was getting in

[Suzsmokeyallan]

I'm curious about this situation and have been in conversation with Dave a few times. Naturally not seeing it firsthand most of any replies would be speculation as to 'what about'.
Therefore a question not asked yet is, are these matching crankcase halves? Check the chisel strike marks on the case joint by the engine sprocket to confirm they are in fact a matched set by their alignment to each other.

[ja-moo]

Hey Ron id you check how much movement the crank has laterally?

[Suzsmokeyallan]

The bearing with the retainer ring should be there on the right inner side by the primary pinion gear. With that and the locator pins in each bearing there should be no lateral play.

[holysmoke]

Rechecked the lateral movement, its pinned in tight. At least I can't detect any movement there. The seal with the retainer ring is there and working along with the bearing pins. What's the right way to check for crank movement? It seems like there would be a possibility for movement since there's probably some play in the bearings? Or are the bearing pretty tight? Anyway I couldn't detect any movement by just grabbing the ends and trying to push and pull. I did notice a vibration at higher RPM's a few hundred miles before the failure. It would vibrate on the highway bars noticeably. It wasn't there before. That may be a clue that something was going on. Could that be caused by the seal starting to hit the journal, or something else?

I wasn't even aware of the chisel marks to denote the matched halves. Yep, I put the halves together and there are two chisel marks near the primary gear and they do line up perfectly.

Interesting concept of the oil pushing the seal out. It's difficult to tell how freely the oil can move through the bearing when its assembled into the crank. That would have to be checked, like you say, when the crank is rebuilt. How much pressure do you think the oil pump can produce? Is it enough to move a seal?

This is great input. I appreciate your help. I'm learning more about cranks, seals, oil flow and bearings, probably more that I ever wanted to.

Bill Bune requested that I send the crank and the casings for him to make an assessment. What's the cost to ship those parts around? Would it be easier to ship in pieces?

Based on what I've seen so far I don't think we can definitely say what's causing the problem. The areas that need to be looked at are the oil flow through that bearing and possibly pinning in the seal better with multiple punch marks, maybe the crank has some lateral movement, but I'm not pushing it hard enough.

Anything other areas we can assess?

Thanks for all the great input,
Ron

[ja-moo]

There is definately something wrong with a vibration, that needs to be addressed. And you can always pin the seal also........

[tz375]

Agree 100%. That vibration is an issue and needs to be understood. It's possible that the seal moved and you were losing power on that cylinder and that was the cause of the vibration. Or did something else cause vibration which allowed teh seal to migrate laterally?

I'd be tempted to drill into the crankcase to take a press fit pin and then drill a matching hole in the seal to locate it in the upper half. If the bikes does not vibrate it was the seal causing it. If it does, the cause still needs to be found and corrected. I have tried the old welding locating nubs on the outside to stop a countershaft seal slipping out, but I'd prefer to use a locating pin if possible.

What prompted you to suspect a blow seal and what pressure testing did you do to confirm that diagnosis and what were the results?

[holysmoke]

I like the idea of a press fit pin, and a few punch marks for good measure. Hopefully the vibration will be gone when I put it back together. I'm going to send the crank out this weekend.

I suspected the seal because I was on a ride and started loosing power. It was right after a short highway run. I finished the ride, but it was getting pretty bad by the time I got home.

I did a leak down test when I suspected the seal. There was no pressure held between L and C, it was open. R passed the 6 pounds for 6 minutes test.

Thanks,
Ron

[tz375]

I'll be very interested to hear what Bill Bune Enterprises find.

Your diagnostic approach is sound, so was it the seal (chicken) or the vibration (egg) that came first? With any luck Bill's technicians will work it out.

[holysmoke]

All right. So I pinned the two seals that can possibly move on the bottom crank half, and added some small punch like knurling on the top case halves. I've got 60 miles so far. I'm keeping my fingers crossed.

I did replace the oil pump with a newer one. The newer style pump doesn't seem to put out as much oil. The old pump did show some wear on the control cam which I think allowed the pump to rise up higher. I'm wondering if that contributed to the theory of oil pushing the seal. I certainly don't see near the smoke I used to.

I think I've got it nailed now, time will tell. Thanks for all the great help.

Ron

[Vintageman]

I did not read all the replies. What I understand is that the seal fails.

I had a seal fail from side to side movement cause by vacuum and pressure of the piston movement (my hypothesis). All else was good witht he crank. Read on if this is one of your thoughts on the matter.

In my case the seal had a rubber lip molded on half of it and was suppose to align with in the case half supplying a mating groove.

Last time, I took a piece of 22 gauge stainless steal wire and cut it to length so it fit in the case half groove. Funny the wire was on a roll and it formed perfectly to the half round diameter of the case without out any further shaping: just sat there nicely. I do get lucky now and again.

The 22 gauge thickness was such that half of the wire was in and half was out. When I placed the seal back in the wire held it in place better. No issues sense.

It was on a twin GT250 inner seal. I was also concerned I was using too much case sealant between case halves. Either way the wire fixed my issue.