New output shaft seal failure

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Lurchio
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New output shaft seal failure

Postby Lurchio » Thu Aug 10, 2017 5:09 pm

Hello fellow fettlers,

Having just changed the clutch on my R1150rt, whilst the box was off I have changed both front and rear input shaft seals, the rear one had failed and caused a big leak which I caught just in time by the looks. (Did the modification to the housing as well!)

There was also a SLIGHT leak at the output shaft seal, so again as the box was off, changed that. All the seals, including the output shaft were carefully measured (vernier) in their installed position before removal as I knew this was important. They were removed using a screw in 'puller' which is essentially two sharp screws on a yoke. The screws go in the seal body and you pull it out. The seals were all replaced by drifting them in with the correct sized drift in every case to the same installed depth as the originals. The spline shafts were wrapped in ptfe tape and that was then oiled to prevent lip damage as the seal installed. Theres no burring on the shaft surfaces, and no movement in the bearings behind the seals.

I noticed that the replacement output shaft seal was different to the old one, there seemed to be a wider 'seal' area, with a correspondingly narrower 'hard plastic' housing area. The other seals for the 'box I had OEM from Madrid, the output shaft seal was out of stock, so I got that from Motorworks UK. A clue maybe?

Took the bike out for its shakedown today, after about 25 miles, stopped and got the smell of frying EP80/90! The output shaft boot was dripping oil onto the collector box, and was then dripping it onto the ground. The oil had also 'flung' back along the swingarm, and got as far as the inside of the tyre, so this is no small leak. Anyway, got the bike home and have removed the swingarm to examine everything.

The leakage is definitely under the output shaft seal, some has gone along the swingarm inner housing, but most has dripped out below, via the bellows. Theres definitely markings on the seal face where it sits around the shaft of rotation where the driveshaft U/J has lightly rotated against the seal face (theres a circle of moly that I lubed the spline with, its not a 'fling' but a circle right on the immediate seal lip area), even though the snap ring in the U/J and the installed depth of the seal are both correct. Theres no obvious damage to the seal, just this circular marking. Weird.

The seal looks okay, but obviously its not!

I have just pulled the seal, and can see a LOT of oil behind the seal housing. I can also see a oil feed in the top of the housing, this was clear and the seal I put in could not have obstructed it. The bearing behind has a fully sealed cage, but I can see a small hole in this, probably caused by the previous removal. (Didn't need to use a 'puller' to get the new seal out). Surely, this wouldn't cause this leak? There cannot be much pressure going on there, so high up the box. The breather is clear by the way.

Any ideas? Could the new type seal have to go in further? Does that hole in the bearing cage seal hold an answer? The hole in it is TINY, like the tip of a bradawl would make.

Thanks very much.

Mike D
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Re: New output shaft seal failure

Postby Mike D » Thu Aug 10, 2017 7:11 pm

The seals used in that application are the later Teflon lipped type. These need to have the lips formed then placed on a sleeve. There are a number of special BMW tools called for in the BMW Service manual that are used to achieve this and to then insert the seal. One set is for the crankshaft end seal and the for the clutch end seal.

Did you use the correct tools?

Mike

Lurchio
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Re: New output shaft seal failure

Postby Lurchio » Thu Aug 10, 2017 8:16 pm

Hi Mike,

I know the situation regarding the crankshaft seals, I have left mine alone as they were not leaking and I didn't have the tools to do that job anyway, I have the BMW manual and could see that the crank seals were a no no . Confirmed that the seals I changed on the gearbox were the usual vitron (or similar) lipped type, with an internal wire/spring around the inside of the sealing lips, not just the plain lip on the crank seals which needed forming and were NOT so fitted with this spring, so getting the 'give' in the Teflon spot on is essential.

In respect of the gearbox seals, the special tools consist of a sleeve and a drift. The sleeve I assume is to protect the seal from the output shaft splines whilst it is drifted in (I substituted this function with PTFE tape and oiled the surface), the sleeve may expand the seal, but the internal spring / wire would surely contract and re align when it hit the plain part of the shaft. Nowhere in the manual (or Haynes) does it emphasise the seals for the gearbox input/output shaft have to be preformed. I stand to be corrected of course.

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Re: New output shaft seal failure

Postby King Herald » Fri Aug 11, 2017 6:24 pm

If you pulled the seal out with no effort, then it was not in tight. Which means it could leak around the out edge. I assume it is like most rubber moulded oil seals, and the interference fit is what seals the outer edge against leakage. You could either try some silicon sealant, or try a different type seal.
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Lurchio
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Re: New output shaft seal failure

Postby Lurchio » Mon Aug 14, 2017 9:36 pm

An update,

The seal looks okay, but theres definitely been some 'blow by' around the housing / seal flange. (Box is off AGAIN..... don't ask). Anyway, checked everything closely, there is a gouge in the gearbox housing where the seal sits. The seal outer will not 'reach' into this, so theres the cause of the leak. Even though I was really careful, it seems that either the drill I used for a pilot hole for the puller, or the pullers screw its self has caused the gouge, which goes all the way into the housing from the outer edge of the flange to the bottom of the housing and is about 1.5mm wide by 1mm deep. Sod it!

Any ideas? I am loathed to use ordinary silicone,I thought JB weld, but the gouge is so small it may not take, and also may expand at a different rate in use and fall away. I have ordered OEM seals, but could do with this being the last time............ Thanks in advance.

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Jaythro
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Re: New output shaft seal failure

Postby Jaythro » Tue Aug 15, 2017 1:40 pm

Use an RTV sealer lightly on the outside

We have to do this when building airhead boxes and using the new "diapraghm" seals

we use a dab of RTV to seal the inverted V at 12 o'clock (The old type rubber seals used to slightly deform into it and seal it)

My Favourite is the Cyclo Grey gasket sealer on all the bikes I build LINK
"Put your Ass on a motorcycle and ride with an attitude and the "Grim Reaper" will ride in your shadow!"

Islandmagee in case you're interested?

Lurchio
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Re: New output shaft seal failure

Postby Lurchio » Tue Aug 15, 2017 3:08 pm

Jaythro,

Thanks for your time and trouble in answering including sending the link! I will go with that then.


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