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Old 04-07-2013, 02:26 PM   #1
backfill OP
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Push rod tube seal help

I have a 1992 R100R; I have owned it about 3 years, but it sat for about 4 years before I bought it and it took me two years to get around to putting it back on the road. So it sat up to 6 years without being ridden.

Oil has been seeping from around the push road tube seals, but I procrastinated all winter about changing them. I rode it yesterday and checked it afterwards. There was quite a bit of oil beneath the seals, so I decided to take it apart to change the seals today. I had ordered all of the parts a while ago, so I had everything on hand.

Anyway, I got one side apart today but there is no rubber O ring at the base of the cylinder were it connects to the engine. There was a bit of sealant around the outside and inside of the base of the cylinder.

So my question is, did i get the wrong parts when I ordered them? Does this year not need the O ring? Or, was somebody previously cutting corners and just didn't put in an O ring?

Any help would be appreciated.

I have added some photos. The first is of the sealant, the second of the top of the piston and the third is of the inside of the head. they look okay to me, but let me know if anything looks wonky. Sorry for the crappy photos, but I only had my iphone for photos.

TIA,
Phil


Sealant at base of cylinder


Top of piston


Inside of cylinder head

backfill screwed with this post 04-07-2013 at 02:56 PM Reason: added some photos
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Old 04-07-2013, 04:18 PM   #2
Cogswell
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O-rings not used on a lot of models, check for chamfer. I just use a bit of yama-honda-kawa-three bond at the base of the cylinder to seal it to the case.


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Old 04-07-2013, 04:19 PM   #3
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They didn't all have orings on the base. IDK the specifics but the gurus will be along shortly to clarify. Will just need a bit of yamabond on the base at reassembly. You're OK.
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Old 04-07-2013, 04:27 PM   #4
supershaft
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That model came with large O-rings. They seal much better with them. Use a very thin layer of Durko or Yamabond. Put just a tiny dab of sealant on the stud O-rings to make them stick in there recesses and make sure they haven't fallen down on to the studs right before the cylinder is synched all the way down on the case. They will deform the cylinder's/case and cause oil leaks if the cylinders are torqued down with the O-rings getting pinched between the sealing surfaces.
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Old 04-07-2013, 07:05 PM   #5
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The large O-rings don't always fit. Get a couple and do a test assembly by trying to put the cylinder on without the piston. If the o-ring is damaged on the test assembly, put it together without it.

Your carbon deposit looks like it is running rich, but with good oil control.
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Old 04-07-2013, 07:48 PM   #6
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Quote:
Originally Posted by bmwrench View Post
The large O-rings don't always fit. Get a couple and do a test assembly by trying to put the cylinder on without the piston. If the o-ring is damaged on the test assembly, put it together without it.

Your carbon deposit looks like it is running rich, but with good oil control.
There are two different sized large O-rings. Use the largest one the still fits correctly. I very carefully lightly oil mine with Tri Flow so that they slide in better and at the same time do not contaminate my sealant. They seal much better with the O-rings. I would not put one together without them. Machining for O-rings is expensive. For some reason, O-rings seal cylinders the best. Even Harley finally figured it out and now uses O-rings on the twin cam engines. They sure did warranty a LOT of base gaskets up until then. The very first really reliable radial aircraft engine used them way back in the late twenties. The Wright J-5. I use to work on Wright J-6's and J-7's the most. Those and Warner Scarabs. Every later radial that I have ever worked on uses O-rings for their cylinder bases. It's what works best.

supershaft screwed with this post 04-07-2013 at 08:07 PM
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Old 04-07-2013, 07:55 PM   #7
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I haven't been able to find the thinner-wall o-ring in years. Where are you getting yours?
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Old 04-07-2013, 07:59 PM   #8
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Bench Mark Works.
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Old 04-07-2013, 10:21 PM   #9
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Quote:
Originally Posted by backfill View Post
I have a 1992 R100R; I have owned it about 3 years, but it sat for about 4 years before I bought it and it took me two years to get around to putting it back on the road. So it sat up to 6 years without being ridden.

Oil has been seeping from around the push road tube seals, but I procrastinated all winter about changing them. I rode it yesterday and checked it afterwards. There was quite a bit of oil beneath the seals, so I decided to take it apart to change the seals today. I had ordered all of the parts a while ago, so I had everything on hand.

Anyway, I got one side apart today but there is no rubber O ring at the base of the cylinder were it connects to the engine. There was a bit of sealant around the outside and inside of the base of the cylinder.

So my question is, did i get the wrong parts when I ordered them? Does this year not need the O ring? Or, was somebody previously cutting corners and just didn't put in an O ring?

Any help would be appreciated.

I have added some photos. The first is of the sealant, the second of the top of the piston and the third is of the inside of the head. they look okay to me, but let me know if anything looks wonky. Sorry for the crappy photos, but I only had my iphone for photos.

TIA,
Phil


Sealant at base of cylinder


Top of piston


Inside of cylinder head
The angle of the photo does not reveal if you have the groove for the o-ring. If you do, put one in it and check fit. It should be tight but go together and come apart in one piece. Lube it when assembling.
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Old 04-08-2013, 09:33 AM   #10
backfill OP
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thanks

Thanks all for your comments. The base of the cylinder does have a groove for a rubber O ring, so i installed it and got it back together. I am now working on the right side cylinder. Again, no O ring. At least it is consistent.

I must say that I haven't taken an engine apart this much in a many years, so I started this with a bit of trepidation. It is actually pretty easy to take an airhead apart. And the second side is going much faster than the first side. I say this now, but I may not be so happy if it doesn't work properly afterwards.

thanks
Phil
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Old 04-08-2013, 04:02 PM   #11
bmwrench
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BMW (supposedly) stopped installing the large o-ring about the time your bike was built. The reality is that some bikes were shipped with the o-ring and some without.
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Old 04-08-2013, 04:25 PM   #12
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O-ring schmo-ring. The buggers leak with a small or large o-ring.
The sealant used, is the key. (imo)
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Old 04-08-2013, 04:41 PM   #13
supershaft
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BMw shipped a lot of O-ringed cylinders with no sealant in the early eighties. IMO, they leaked less there than they did with gaskets. My '83 LS had no sealant on it and they never leaked. That lasted 60,000 miles until I took it apart for a valve job.
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Old 04-08-2013, 06:05 PM   #14
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I would not expect to find O-rings as late as '92. That looks like original sealant to me. No harm using O-rings, but use sealant also. I use Yamabond gray.
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Old 04-08-2013, 08:12 PM   #15
supershaft
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Funny, I have worked on a lot of '92's that had O-rings from the factory according to the service history. My own '92 did. I don't remember getting into one single later model that didn't have them. I hope I was clear in that I always reassemble them with O-rings and sealant. I have had good luck with them not even weeping at all like that.
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