BMW R80ST technical questions on re-assembly

bpeckm · 01-29-2013, 10:58 AM

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....

Airhead Wrangler · 01-29-2013, 11:01 AM

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.

One Less Harley · 01-29-2013, 11:04 AM

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.

Prutser · 01-29-2013, 11:10 AM

I use the gasket from the older ones on all my mono's and never had a problem with them.

bpeckm · 01-29-2013, 11:17 AM

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!!

mark1305 · 01-29-2013, 12:09 PM

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.

BMWrider79 · 01-30-2013, 05:03 AM

Quote:

Originally Posted by bpeckm

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.

bmwrench · 01-30-2013, 05:12 AM

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.

bpeckm · 02-03-2013, 01:11 PM

...

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?

BMWrider79 · 02-03-2013, 02:21 PM

Quote:

Originally Posted by bpeckm

...

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

bpeckm · 02-04-2013, 08:12 AM

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.

bpeckm · 02-04-2013, 06:39 PM

Are the four holes-in-a-row to provide a forward and a back place to put the standard BMW bar mounts?

villageidiot · 02-04-2013, 06:53 PM

Quote:

Originally Posted by bpeckm

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.

bpeckm · 02-05-2013, 03:24 PM

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....)

BMWrider79 · 02-05-2013, 08:56 PM

Quote:

Originally Posted by bpeckm

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

01-29-2013, 10:58 AM	#1
bpeckm ^OP Grin! Joined: Apr 2008 Location: Road Island Oddometer: 4,441	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.... __________________ XS650 becomes a Vermont Backroader R60/6 gets caffeinated Portsmouth RI

01-29-2013, 11:04 AM	#3
One Less Harley OH.THAT'S GONNA HURT Joined: Nov 2006 Location: Bowling Green, Ky Oddometer: 3,926	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. __________________ 2004 BMW R1150RS 1984 BMW R80G/S (wrenching index) 2003 Suzuki DRZ 400S (TAT Prep) One More DRZ does the TAT (Ride Report)

01-29-2013, 11:10 AM	#4
Prutser Studly Adventurer Joined: Aug 2012 Location: The Dutch swamp Oddometer: 517	I use the gasket from the older ones on all my mono's and never had a problem with them. __________________ BMW R100'91/R80'93/R80ST'83/R65GS'87/GasGasTXT300/DouglasW20-1920 R100GS'91 (sold)

01-29-2013, 11:17 AM	#5
bpeckm ^OP Grin! Joined: Apr 2008 Location: Road Island Oddometer: 4,441	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!! __________________ XS650 becomes a Vermont Backroader R60/6 gets caffeinated Portsmouth RI

01-29-2013, 12:09 PM	#6
mark1305 Old Enough To Know Better Joined: Feb 2005 Location: Merritt Island, FL Oddometer: 5,527	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. __________________ Mark J Merritt Island, FL When a person asks you for advice, they don't want advice. They want corroboration.

01-29-2013, 11:01 AM	#2
Airhead Wrangler More tacos than you Joined: Mar 2008 Location: Manzanillo MX, occasionally Seattle Oddometer: 5,201	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. __________________ R80ST Gets The HPN Treatment Ducati Pantah 500SL Rebuild Seattle to TDF on an airhead WTB R100R Mystic sidestand and mount.

01-30-2013, 05:12 AM	#8
bmwrench Beastly Adventurer Joined: Nov 2006 Oddometer: 1,483	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.

02-03-2013, 01:11 PM	#9
bpeckm ^OP Grin! Joined: Apr 2008 Location: Road Island Oddometer: 4,441	... 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? __________________ XS650 becomes a Vermont Backroader R60/6 gets caffeinated Portsmouth RI

02-04-2013, 08:12 AM	#11
bpeckm ^OP Grin! Joined: Apr 2008 Location: Road Island Oddometer: 4,441	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. __________________ XS650 becomes a Vermont Backroader R60/6 gets caffeinated Portsmouth RI

02-04-2013, 06:39 PM	#12
bpeckm ^OP Grin! Joined: Apr 2008 Location: Road Island Oddometer: 4,441	Are the four holes-in-a-row to provide a forward and a back place to put the standard BMW bar mounts? __________________ XS650 becomes a Vermont Backroader R60/6 gets caffeinated Portsmouth RI

02-05-2013, 03:24 PM	#14
bpeckm ^OP Grin! Joined: Apr 2008 Location: Road Island Oddometer: 4,441	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....) __________________ XS650 becomes a Vermont Backroader R60/6 gets caffeinated Portsmouth RI

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