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Old 01-29-2013, 11:58 AM   #1
bpeckm OP
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BMW R80ST technical questions on re-assembly

I am putting my ST back together after doing some "maintenance" and have a few questions.... I want to do a thread on the whole dis-assembly and re-assembly, which I will (eventually!), but for now I have some ho-um, somebody can certainly answer THIS type of questions.....

First question, there is not a gasket spec'd nor a part number for said gasket between the driveshaft and the final drive. When I dis-assembled, there WAS a gasket, and every other twin- or mon-shock I have ever done DID have a gasket. I can certainly re-assemble with Yamabond or some such, but wondered what y'all have done..... (I got parts from Max, and asked them, and they said that the fiches don't show a gasket, so there isn't one, .........but.......)



It would be a square-ish gasket with a big round hole in the middle, with four bolt holes for studs #2..... you know, the standard, every-airhead-final-drive gasket....
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Old 01-29-2013, 12:01 PM   #2
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Someone speak up if I'm wrong, but I believe BMW eliminated that gasket and now advises to assemble it metal to metal with a sealant. I used threebond there.
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Old 01-29-2013, 12:04 PM   #3
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I'd make a gasket, as I wouldn't trust sealing to just yamabond or equivalent.

BTW- I've had mine apart but don't remember what was done.
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Old 01-29-2013, 12:10 PM   #4
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I use the gasket from the older ones on all my mono's and never had a problem with them.
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Old 01-29-2013, 12:17 PM   #5
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Yeah, I hadn't thought of that... I guess I could use the old standard twinshock piece...I have used Yamabond on the inside cases of a Yammy motor, and it is fabulous stuff, but somehow I would feel better with an Old School Gasket in this application!



04 33 17 2 311 098 GASKET ASBESTOS FREE 1 $1.79

Price is right!!
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Old 01-29-2013, 01:09 PM   #6
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Hi Bob.

I ran into a similar situation when I split my first Ducati 900 motor open for a spun rod bearing. Ducati eliminated the gasket in the middle of the crankcase. Threebond had just come out with the 1194 stuff. It worked so well that when I had to reopen the case to correct a shimming error, I had to make special tools up to get the two halves apart.

Where clearances and shimming come into play, on the Ducs the allowance for the old gasket was .011" (from an unused .015" thickness). When using Threebond applied properly (thin) the allowance changed to nil.

I'd use it and not look back.
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Old 01-30-2013, 06:03 AM   #7
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Quote:
Originally Posted by bpeckm View Post
I am putting my ST back together after doing some "maintenance" and have a few questions.... I want to do a thread on the whole dis-assembly and re-assembly, which I will (eventually!), but for now I have some ho-um, somebody can certainly answer THIS type of questions.....

First question, there is not a gasket spec'd nor a part number for said gasket between the driveshaft and the final drive. When I dis-assembled, there WAS a gasket, and every other twin- or mon-shock I have ever done DID have a gasket. I can certainly re-assemble with Yamabond or some such, but wondered what y'all have done..... (I got parts from Max, and asked them, and they said that the fiches don't show a gasket, so there isn't one, .........but.......)



It would be a square-ish gasket with a big round hole in the middle, with four bolt holes for studs #2..... you know, the standard, every-airhead-final-drive gasket....
So I have a '83 ST that I'm building right now. There is no gasket used -instead you should use a sealant that is intended for torqued joints. Many kinds are on the shelves - I chose a loctite offering. BMW advised using Loctite 518 you could also use Loctite 573.

BMWrider79 screwed with this post 01-30-2013 at 06:07 AM Reason: Adding info
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Old 01-30-2013, 06:12 AM   #8
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I believe that BMW thought there would be enough movement of the monolever rear drive to eventually destroy a gasket, so they recomended sealant. Apparently they thought sealant was immune to this.

I've assembled them with and without gaskets. The joint didn't leak either way.
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Old 02-03-2013, 02:11 PM   #9
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...

Thanks to all who staightened me out on the above ^ !!







OK... so the next "technical" question.....


If the 80ST is considered one of the best-handling airheads every built, is there ANY difference in the TRIPLE-TREE itself (not the forks, suspension etc....) ??


The reason I ask this is that the 80ST has that same scrawny airhead top-plate for the triples that experts here deride with some regularity.... yet I don't hear a lot of talk of a better top? I know that "those who convert" to a G/S style often do a different/better front end but that is primarily for fork travel, and somewhat for brakes, than for handling.....





The stem bearings are cross-referenced to pretty much all airheads starting with the /6 series. The actual top- and bottom units are shared with the R65 and the G/S, and vary only by some minor fasteners (for the R65 and ST headlight assembly).... but .... is it the same bottom/top dimensionally?

Anybody care to throw out their thoughts on that?
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Old 02-03-2013, 03:21 PM   #10
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Quote:
Originally Posted by bpeckm View Post
...


The stem bearings are cross-referenced to pretty much all airheads starting with the /6 series. The actual top- and bottom units are shared with the R65 and the G/S, and vary only by some minor fasteners (for the R65 and ST headlight assembly).... but .... is it the same bottom/top dimensionally?

Anybody care to throw out their thoughts on that?
You are correct that they are the same. If you plan on doing a lot of off road it would perhaps be best to look at all the people who have done some really neat conversions to ST and G/Ss. As well, the front suspension is not the best (even by BMW standards).

For myself adding a Toastertan top plate, http://www.pbase.com/toastertan/top_braces
and Racetec (the US company) emulators was enough.

If you use the TT top brace you will need to add two holes for the headlight mounting bracket.
From BMW R80ST

Good luck

BMWrider79 screwed with this post 02-03-2013 at 03:22 PM Reason: missing words
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Old 02-04-2013, 09:12 AM   #11
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Wow... that picture is worth the proverbial 1k words.... I suspected, but wasn't sure, and to see the two tops "side-by-each" is just perfect.





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Old 02-04-2013, 07:39 PM   #12
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Are the four holes-in-a-row to provide a forward and a back place to put the standard BMW bar mounts?


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Old 02-04-2013, 07:53 PM   #13
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Originally Posted by bpeckm View Post
Are the four holes-in-a-row to provide a forward and a back place to put the standard BMW bar mounts?


yes

the toaster tan unit is a VERY nice piece, and hes a super guy to boot.
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Old 02-05-2013, 04:24 PM   #14
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Ok.... another thing to put on the KaChing list.... nice indeed! .......Nothing like a little triple-porn to look at on his website..... sigh.....(yes, it is SFW....)

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Old 02-05-2013, 09:56 PM   #15
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Ok.... another thing to put on the KaChing list.... nice indeed! .......Nothing like a little triple-porn to look at on his website..... sigh.....(yes, it is SFW....)

Toastertan is a good dude. I stopped by his place last year just to meet him (and get a brace for my '81RS)- in fact he has some photos of it on his site here http://www.pbase.com/toastertan/vincent
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