Author Topic: Rear main seal tool  (Read 5834 times)

Offline Filmcamera

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Rear main seal tool
« on: May 17, 2018, 05:18:54 PM »
This weekend I plan on replacing the leaking rear main seal on my bike.  To that end I went to my local machine shop and for $40 they made me this.








It is made of hard nylon wich they swear is a better solution than metal - we will see.


0.5mm is not very much when you see it live is it?


Anyway I am glad to be going in to the clutch etc because the bike has recently developed a nasty rattle that goes away when I pull the clutch - it is not there all the time, only when the bike is fully warm and after some spirited riding - i.e- 7,000 - 8,000 revs.


Since I am going to have the bike apart I plan to check the valves and also have a look at the timing chain whilst I am at it - and throw in an oil change for good measure.


Going to be a busy weekend but i need to get it done since I have a three hundred mile all day group ride on June 3rd.


Are there any other common causes of a rattle from the engine in the 2,000 to 4,000 range I should be looking for?







  • San Jose, Costa Rica
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Offline Filmcamera

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Re: Rear main seal tool
« Reply #1 on: May 19, 2018, 09:26:52 PM »
I did most of the tear down to replace the rear main seal today.  Huge amoUnts of oil leaked out of the clutch boot when I removed it so it is clearly time this job was done!











I hope to get it finsihed tomorrow
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Offline Scott_

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Re: Rear main seal tool
« Reply #2 on: May 19, 2018, 10:10:39 PM »
Not to burst your bubble, but you should have oil in the clutch boot...... transmission oil.  That is what keeps the thrust bearing lubricated.
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Offline Filmcamera

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Re: Rear main seal tool
« Reply #3 on: May 20, 2018, 07:45:16 AM »
I am not sure I should have it all over the clutch and housing though. 
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Offline Scott_

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Re: Rear main seal tool
« Reply #4 on: May 20, 2018, 07:56:09 AM »
I am not sure I should have it all over the clutch and housing though.

I good sniff test should help determine which oil is where.... Not unheard of for the motor oil from a broken/old/dried-up clutch nut o-ring to coat the clutch, not saying it can't be the motor output main seal but the o-ring failure is way more common than a bad seal.

If the oil coating the clutch is transmission oil,(hence the obvious sulfur odor) you have other issues than the engine output shaft seal. Could be the transmission input shaft seal. If you think the transmission oil is migrating up the clutch push-rod, it should be coated with oil when you take it apart and there is an o-ring internal to the transmission input shaft that you will need to replace.
  • My Garage
1995 K1100LT 0302044
1997 R1100RT ZC62149
2017 FLHTK Ultra Limited
1997 K1100LT 0302488 (R.I.P.)
"One who does not ask questions is ashamed to learn" Danish proverb

Offline Filmcamera

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Re: Rear main seal tool
« Reply #5 on: May 20, 2018, 10:10:24 AM »
Scott I have a feeling you are right - I have got all the way to the rear main seal and it looks in ok shape to me





however this morning I found this by the tranny





When I took off the clutch housing it had this much oil on it





Does that look about normal?


There is a kind of sulfur smell from the oil that is on the housing etc.


I had changed the seal on the transmission so had not thought it was them - then I remembered I later changed the transmission...


Before I take out a possibly perfectly good seal what do you think?
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Offline Scott_

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Re: Rear main seal tool
« Reply #6 on: May 20, 2018, 02:38:09 PM »
I see a couple of things.
1, the oil under the transmission, most likely came out of the opening where the clutch boot mounts. The thrust bearing that sets inside the boot is lubricated by transmission oil, if the transmission is setting level or front end higher than back end, you are going to leak oil out of that opening. I will say that the trans oil is nasty looking. I've done the same thing myself. Set the transmission to the side and it started leaking oil out of that opening.

2, the oil pattern on the back side of the clutch basket looks to be from the inside of the basket, indicating a failed clutch nut o-ring, or transmission input shaft seal. The backside surface of the middle section(that is rivetied) looks to be dry up to the point that the hub rides on the seal.
I'd probably say that the seal was good, but, as long as you have the bike apart to this point, and if you have a seal, you might as well replace it.

I've not tried to replace the push-rod o-ring that is located internal to the transmission input shaft, I have read of others that have managed to get the old one out and new one in with some small dental tools. As far as the transmission input shaft seal, it might be a good time to replace it if you have no idea on age/mileage of the transmission.
  • My Garage
1995 K1100LT 0302044
1997 R1100RT ZC62149
2017 FLHTK Ultra Limited
1997 K1100LT 0302488 (R.I.P.)
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Offline gone_ape

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Re: Rear main seal tool
« Reply #7 on: May 20, 2018, 02:42:56 PM »
How old is that seal?  From what I can see it looks fairly dry.... the oring may have just started to let slip past it...it could be remnants of moly spline lube too.  I.E., not too bad.  As long as you're in there, just replace it....
Consider taking a strip of 2000 grit emery paper and polish the clutch housing shaft that slips into that seal...
You can make a simple driver from a 3 /12" flat washer adhesive silicon sealed to a large socket....
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Offline Scott_

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Re: Rear main seal tool
« Reply #8 on: May 20, 2018, 05:00:22 PM »
GA, that would work fine on the 8v motors, according to BMW though, on the 16v motors the seal is not supposed to be flat/flush with the block. It is supposed to be .5mm proud of the block surface.
  • My Garage
1995 K1100LT 0302044
1997 R1100RT ZC62149
2017 FLHTK Ultra Limited
1997 K1100LT 0302488 (R.I.P.)
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Offline rbm

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Re: Rear main seal tool
« Reply #9 on: May 20, 2018, 07:30:05 PM »
That main seal looks to be older but it's a fuzzy picture.  The modern seals being sold by BMW are brown coloured PTFE with a black metal surround.  This one is not brown and doesn't look quite black either.  So, unless you know when the seal was last replaced, you cannot go wrong by replacing it with a new one.  You've come this far so why not take 1/2 hour extra to put your engine at a known state.
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Offline Filmcamera

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Re: Rear main seal tool
« Reply #10 on: May 20, 2018, 08:58:51 PM »
The seal that is in there is metallic as far as I can see. 


On the whole I think you are right and that since I have come this far I may as well change it out.
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Offline rbm

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Re: Rear main seal tool
« Reply #11 on: May 20, 2018, 09:28:04 PM »
You have to take that metal washer out first to see the seal wiper and make that assessment. 

BTW, I agree with Scott that the pool of oil under the transmission could have come from the push rod area where the clutch boot should sit if the transmission was allowed to sit on the centre stand mounting legs or if it lay facing downwards.
  • Regards, Robert
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1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline Filmcamera

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Re: Rear main seal tool
« Reply #12 on: May 20, 2018, 09:31:56 PM »
Yes there was oil leaking from the transmission but as you say that could just have been from how it was sitting after taking it off.  I started this whole process because the bike was 'marking her territory' quite a lot and there was oil all over the belly pan and the bottom of the engine.  So something somewhere is leaking and it is just a matter of working out what. I thought/hoped it was the rear main seal because that might have helped to explain part of the excessive oil usage.
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Offline wally.fisher

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Re: Rear main seal tool
« Reply #13 on: May 22, 2018, 01:33:31 PM »
I use the clutch housing to pull the new seal in , just remove the fibre spacers from the housing and wind the new in using the old nut, this gives the 0,5mm needed, just remember to refit the fibre spacers and fit a new Vito O ring on reassembly.


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Offline Filmcamera

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Re: Rear main seal tool
« Reply #14 on: May 26, 2018, 10:57:53 AM »
New rear seal went in a treat, the whole bike is back together and running well, my local muffler shop even managed to do a pretty decent job off welding the exhaust back together  :riding:


I did notice that both bearings in the rear swing arm are basically destroyed.  Max BMW wants $100 each which seems crazy - has anyone found an alternative option?


11
33 17 2 311 091 NEEDLE BEARING - 10X32X17
0.09
$100.25

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Offline rbm

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Offline Filmcamera

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Re: Rear main seal tool
« Reply #16 on: June 05, 2018, 02:23:42 PM »
Thanks RBM - I have ordered a set.


A quick update.


After changing the seal I went ahead and did an oil change at the same time, the first I have done myself on the bike.


I was worried about how tight the oil filter would be but if anything I had the opposite experience.  When I put the oil filter wrench on the one that was there I initially thought it was the wrong one because it moved so easily.  I then realised that was because the oil filter was totally loose!



After changing the oil I added some Bardahl 2 oil treatment for high mileage engines that smoke and use lots of oil.


This weekend I did 125 miles or so of sometimes pretty hard riding and have not used a single drop of oil!  No idea if it was the rear main seal, the loose filter or if it is the Bardahl 2 stuff but either way I am very happy so far.


Long may it last!
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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