Crank Seal Replacement?

All this talk about wet-sumping has left me paranoid. If I don't have a valve, I must drain the case after a couple of week sitting I guess. If I don't it is said I may blow a main seal. So if I gamble and don't drain, what is the risk? How hard are the seals to replace? Do i have to split the cases, or are they installed from the outside.
I've had this bike for 38 years and ignorance was bliss. Now that I'm informed, I'm worried.
Jaydee

Hello and happy new year. You should periodically check your seal and maybe buy a spare just in case. You are right to be concerned about wet dumping but you are doing the right thing. Take good care of the threads on the drain and do not strip them during the process.
I installed check valve drains on few bikes and am having second thoughts after one of them stuck closed after a prolonged shutdown. An oil pressure gage told me that things were amiss before major damage. I am seriously considering taking the check valve out and just draining the sump before starting. Most of us do not take our bikes out enough to make draining the sump a big deal. There are lots of interlocked oil valve options out there or just install a manual stop and remember to open before starting. Kind of like a "remove before flight" tag on aircraft!
Changing out the seal without splitting the cases is easy but be careful not to nick the crank sealing surface. I had one crank the required that I lap down the seal to make it seal in a "new" spot on the crank.
Mike

It all depends on how quickly the contents of the oil tank end up in the sump. My Mk3 takes quite awhile to do this, maybe two months, but then the Mk3s have a semi functional antidrain valve built in. If the oil tank is still half full or better, I go ahead and start the bike without draining the sump. Just keep the revs fairly low for a couple of minutes or so if you ride away. I got a little frisky with the throttle a little too soon with a full sump once and did blow the seal, but it is not a huge job to change it. If you blow the seal you find out pretty quickly as the primary will fill up. When you remove the level plug lots of oil will drain out, rather than the usual drip or two.
As Jim Comstock and others have suggested, as long as you dont blow the seal, it is probably better to cold start a bike that is sitting with a bit of an overfull sump rather than one that is dry as a stick. This way the cam gets a good splash of oil right away.

My 650 ss wet sumps very quickly and also leaks badly when it does, so it is the bike I plan to fit a valve to. As far as cam lube and cold starts are concerned, the plan is to shut the oil off after a few days of sitting when about 1/3 of oil tank contents are in the sump. The crankcase doesnt leak at this level, it is when the other 2/3 of the oil goes in that the incontinence begins.

Glen

so no problem for 38 years and now your worried because of some pundits blathering on an internet forum? :shock: :mrgreen:

jaydee75 said:

....
I've had this bike for 38 years and ignorance was bliss. Now that I'm informed, I'm worried.
Jaydee

Click to expand...

Pundit humanoid here. I've never gotten more than 12 ish years service from a crankseal myself ,but that was before fitting the reed valve to lower the crankcase pressures. 6 years back so let's see. I've always changed them as a matter of course whenever primary work is done.

IF you are really concerned about a LOT of oil blowing the seal into the primary then....

here is what I have always done with my Commandos:

when you start the bike have it leaning a bit to the right and keep it leaning that way after it starts for about one minute, and keep the rpms steady at little over 1000 with throttle hand and choke off quickly

that way the sump oil stays away from the left side where the primary seal is until it returns to the tank

maybe I am lucky but I have yet to have motor oil leak into the primary or blow the seal this way

Check level of tank when you stop engine then again before you try starting it after its been standing for a period of time if it drops an its not all over floor then its in the cases. Over time you will learn what to expect from your bike I may take a day a week or a year. But if you notice its gone down you can take the drain out of bottom an drain it or if it takes a long time like say over a month just use it or start it more often than that.
I have a manual stop valve by John Epp (he's in Canada search his name on this website) it has an electric switch wired to ignition so no oil no sparks an no worries of wet sumps. I got it as like you I worried about all the reports of doom then I found my oil pump is like new inside with no ware at all an even if I leave valve open for month the level in tank doesn't drop so like I say check your bike you may not need to worry .

jaydee75 said:

All this talk about wet-sumping has left me paranoid. If I don't have a valve, I must drain the case after a couple of week sitting I guess. If I don't it is said I may blow a main seal. So if I gamble and don't drain, what is the risk? How hard are the seals to replace? Do i have to split the cases, or are they installed from the outside.
I've had this bike for 38 years and ignorance was bliss. Now that I'm informed, I'm worried.
Jaydee

Click to expand...

First of all, blowing some oil past the seal is not "Blowing" the seal.
Seals are cheap,plentiful and easy to replace. No need to split the case, only to remove the crank sprocket (and all that may entail) to reveal it. Drill a small hole in one or two places, screw in a sheet metal screw and pry in out with a small pry bar or nail remover. Tap in a new one and away you go.

Thanks for the good replies. We've had a lot of rainy weather here so I haven't started the bike in 6 weeks. I'm running 20w-50 and the oil level is down where I can see the top of the screen. Is that too much?
For 9 or 10 months out of the year, it won't sit more than a week. So maybe I can live with it. But I've just reinstalled my electric start, so that could aggravate the situation.
Either way, it doesn't sound like too much trouble to change a seal if necessary and I like the idea of splashing the cam a little on start-up.
Jaydee

Send the timing cover and pump to amr in arizona

The 850 MkIII crank seal is retained by a circlip, so theoretically at least, it shouldn't blow out.

If I know I won't be using my Commando for a while, I usually transfer around half the contents of oil tank to a container using an oil suction gun, the oil can then be poured back into the tank again shortly before start-up.

I did find that adding a restriction to the end of the suction gun tube does make the job less messy as the oil does tend to dribble from the tube during the transfer process otherwise.

When my mk3 seal let go it was still in position however the id part of the seal had rolled around and was facing outward rather than inward as it must to seal.
Glen

You could if the bikes been laid up over winter or for a long enough time just use it as a reason to change oil anyway as you are missing with drain plugs an oil tank levels.

I just sent mine to AMR a few days ago because my combat wetsumps very badly. After 3 weeks of sitting, I had over 30 ounces drain into the sump. (That is with SAE 50 and 20 degrees outside too). With that much cold oil in the sump and 10:1 compression, it's freaking difficult to kick over. I hope the AMR mod at least reduces the seeping.