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Old 03-02-2011, 12:35 PM   #1
Weaverman OP
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R100 jug sealing

A call out for experienced advice! I'm not an airhead guru.

I'm getting ready to button up the top end on my '94 GS. When I pulled the jugs off the old girl I noticed the factory used a small amount of sealant on the jugs...no o-ring or gasket. the fiche shows an o-ring, which I bought when I ordered my parts. The Haynes manual, with pics based on older models, shows a base gasket. The barrel is clearly machined to accept a ring, and the mating half in the case appears ready as well. I don't recall Snobum saying anything about this.

What do you regular builders say??
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Old 03-02-2011, 01:40 PM   #2
Andy-Gadget
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Should be O ring only, but a PO may have fitted decompression spacers, but even with them, the O ring should be used on the pot side.

BTW, there are three O rings per pot, a big one for the barrel base, and two small ones for the top two head studs, they are Viton or silicon high temp ones, DO NOT repalce with cheap butyl rubber ones, or you will get good at pulling the barrels

The main problem here is the top two head studs are the oil feed to the rockers, so an ample slather of wondersnot will stop this oil as well as the leaks, not good.

If the bike has been pinging, then fit lower compression pistons, and bin the compression reducing spacers (a /5 and /6 holdover BTW) and fit the O rings.

If you do decide to go the wondersnot path, use Loctite 515, NOT stag or any other hardening sh1t.
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Old 03-02-2011, 02:18 PM   #3
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Thanks Andy! Yes, I'm hip to the rest of it. I just wondered about the base o-rings v. sealer. this bike has never been apart, so the factory used sealer, not a ring. If everyone puts them together with the ring, then I'll proceed with that plan. I have all the proper BMW pieces.

Also, for elastoeric sealing rings and the like I use Dow silicone grease...really helps in every way.
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Old 03-02-2011, 02:36 PM   #4
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BMW has used a few methods for sealing the base. Including at one time no gaskets or orings just sealant. I would use the o ring as long as the groove is there and I've found dipping it in motor oil just before installation will help it seal. Maybe they were out of orings that day, frankly wouldn't suprise me!!

I should have mentioned I do use a thin smear of sealant also. Orings and sealant, something like hondabond. By thin I mean as thin as you can possibly make it!
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jtwind screwed with this post 03-03-2011 at 07:11 AM
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Old 03-02-2011, 02:51 PM   #5
jackd
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That's wierd, my '94 GS came with the o-rings and a fine film of sealant on the jug bases as well - when I did my top end. I used sealant and new o-rings when I threw it together.
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Old 03-02-2011, 02:58 PM   #6
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thin skin

I've used a VERY thin skin of Hylomar or similar on the jugs. Making sure that there are no blobs or excess near the upper studs where the smaller O-rings go. I have had sealing success with and without the big O-rings, but I do lube the O-rings before assembly. No sealer on the pushrod seals as they need to be able to move in place.
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Old 03-02-2011, 06:22 PM   #7
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My advise is sealer and o-rings.

I use a flat bladed Exacto knife to spread a very thin layer of Durko on the cylinder base. I use just a tiny spec on the stud o-rings to get them to stick into their recesses. I double check and insure that they have not fallen out of their recesses right before the cylinder is synched all the way down. I have found MANY cylinders permanently F'ed up for those stud o-rings falling out on assembly and getting pinched. That rubber WILL move metal!

I lube the cylinder o-ring with a thin coating of Tri-Flow. I otherwise make ALL the surfaces absolutely oil free.

I install the push rod tube seals dry. I do rub of the seal's release agent off with Scotch Brite.

I adjust rocker arm end play with a modified ViseGrip C clamp. It REALLY helps getting that play right down to zero.
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Old 03-02-2011, 06:40 PM   #8
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My 1978 R100S Engine didn't have base o-rings or base gaskets, just the pushrod tube o-rings. No grooves for o-rings that I can see. My parts supplier (Huckys) tells me that there are no base gaskets that will fit that year engine.(?) A knowledgable BMW mechanic tells me that some year engines used nothing but a sealant... I assembled it with a tiny bit of sealant and now the right side is leaking.....back apart it will come when I get tired of the oil drip it's leaving. I bought a pair of base gaskets which I will attempt to fit when I tear it down. The slightly lower compression shouldn't hurt anything.(?)
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Old 03-02-2011, 07:11 PM   #9
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Supershaft - I saw the "push rod seals" (not the pushrod tube seals) on the breakdown, but my bike doesn't have any. The quantity on the breakdonw has an "x" in the box. What are these about? I'm hip to the pushrod tube seals.

The referemce fiche was at Max BMW's site.
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Old 03-02-2011, 07:24 PM   #10
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Quote:
Originally Posted by jtwind View Post
bmw has used a few methods for sealing the base. Including at one time no gaskets or orings just sealant. I would use the o ring as long as the groove is there and i've found dipping it in motor oil just before installation will help it seal. Maybe they were out of orings that day, frankly wouldn't suprise me!!

I should have mentioned i do use a thin smear of sealant also. Orings and sealant, something like hondabond.

This is your answer.
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Old 03-02-2011, 07:51 PM   #11
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I have a '94 R100R, no O ring on the left side. Never had the right side off.
Look at the cylinder base. If it needs an O ring there will be a grove there. If not don't put one there, just use a sealent. Check out Ted Porter's website he hs a photo of how much to use.

Ed
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Old 03-02-2011, 07:52 PM   #12
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The barrel O ring just sits in the corner between the barrel spigot and the base, there is a chamfer on the outside of the case bore that the O ring seats itself into, nice and simple.
But it is the lack of this chamfer that stops you using O rings on older cases, and the lack of the machined recess on the top stud holes that stops the use of O rings here on early barrels, but old barrels on new cases (why would you?) could run the base O rings only.

Quote:
Originally Posted by bmwhacker View Post
My 1978 R100S Engine didn't have base o-rings or base gaskets, just the pushrod tube o-rings. No grooves for o-rings that I can see. My parts supplier (Huckys) tells me that there are no base gaskets that will fit that year engine.(?) A knowledgable BMW mechanic tells me that some year engines used nothing but a sealant... I assembled it with a tiny bit of sealant and now the right side is leaking.....back apart it will come when I get tired of the oil drip it's leaving. I bought a pair of base gaskets which I will attempt to fit when I tear it down. The slightly lower compression shouldn't hurt anything.(?)
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Old 03-02-2011, 08:44 PM   #13
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Quote:
Originally Posted by bmwhacker View Post
My 1978 R100S Engine didn't have base o-rings or base gaskets, just the pushrod tube o-rings. No grooves for o-rings that I can see. My parts supplier (Huckys) tells me that there are no base gaskets that will fit that year engine.(?) A knowledgable BMW mechanic tells me that some year engines used nothing but a sealant... I assembled it with a tiny bit of sealant and now the right side is leaking.....back apart it will come when I get tired of the oil drip it's leaving. I bought a pair of base gaskets which I will attempt to fit when I tear it down. The slightly lower compression shouldn't hurt anything.(?)
O-rings were added...when?...in the 80s? Base gaskets are not for sealing, rather, they were added to lower compression on /6 era motors that started pinging when gas went south.
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Old 03-02-2011, 09:40 PM   #14
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Quote:
Originally Posted by fishkens View Post
O-rings were added...when?...in the 80s? Base gaskets are not for sealing, rather, they were added to lower compression on /6 era motors that started pinging when gas went south.
I am guessing 78/79?

/5's and /6's have base gaskets for sealing. You could order special thicker gaskets to reduce pinging and a lot of people did but a R90S that has 9.5:1 has base gaskets.
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Old 03-02-2011, 09:56 PM   #15
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Quote:
Originally Posted by supershaft View Post
I am guessing 78/79?

/5's and /6's have base gaskets for sealing. You could order special thicker gaskets to reduce pinging and a lot of people did but a R90S that has 9.5:1 has base gaskets.
SS, thanks for the correction.
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