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Old 10-01-2011, 01:25 PM   #16
caponerd
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Location: Halfway between Munich and Redditch.
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Good find.

You have to wonder why it got parked after only 5 years of use? Based on where some of the dust is located (didn't just settle there out of the atmosphere), those were possibly a pretty hard 7300 miles.

I hope you don't find any disasters hiding inside the engine!

I run only premium in both my old BMW's; R100 and R69S. Whenever I'm able, I stop at a gas station near a local lake that's popular with boaters and buy non-alcholhol blend premium.
They'll fill motorcycles, old cars, boat motors and garden equipment, but not modern cars and trucks.
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Old 10-01-2011, 03:32 PM   #17
_cy_ OP
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Location: Tulsa, Oklahoma
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Quote:
Originally Posted by jackd View Post
Lucky you on finding this bike. As to your question on the need to use premium gas in your bike. A Triumph T100 that I restored had a compression ratio of 9:1 and I ran it on today's premium. If I really loaded it, it would still ping on occasion, so I made damned sure I never used regular gas. Seeing as your RS is 9.5:1, I would not even contemplate using regular gas. You have too nice of a bike to go for the less expensive grade of fuel. Put the additional cost of premium fuel as one of the expenses that come with owning a premium bike.
Quote:
Originally Posted by caponerd View Post
Good find.

You have to wonder why it got parked after only 5 years of use? Based on where some of the dust is located (didn't just settle there out of the atmosphere), those were possibly a pretty hard 7300 miles.

I hope you don't find any disasters hiding inside the engine!

I run only premium in both my old BMW's; R100 and R69S. Whenever I'm able, I stop at a gas station near a local lake that's popular with boaters and buy non-alcholhol blend premium.
They'll fill motorcycles, old cars, boat motors and garden equipment, but not modern cars and trucks.
question about running premium fuel is not about costs, but where R90S is limited for touring fuel wise. remote parts of the world where I'd like to go eventually, one cannot be picky about fuel.

the story as told to me by the original owner's son. when the baby arrived, mom told him it was the bike or the kid. so R90S got parked. the son has never seen his dad ride the BMW ever.... he's 30 years old. he told me repeatly, his dad LOVED that bike!

the R90S was stored inside a large shed in his back yard all these years. all the oxidation is from 30 years of 100f summers and below zero winters. Original owner was a Electrical Engineer with American Airlines. My feelings is he babied the R90S the 7,300 miles it was ridden.
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Old 10-01-2011, 04:13 PM   #18
fishkens
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Originally Posted by _cy_ View Post
notice the entire engine is painted black, not just cylinder base. this was pointed out to me by several Adv members already. No question this was done at the factory as engine has never been out. all the factory tie straps are still intact.
Nice find of a great bike.

I'm curious about the engine case, trans, etc. being painted black at the factory. Is the original owner still around to confirm? Has anyone ever heard of BMW painting the cases black (before the K-bikes)? Just curious.

Any mods other than the rear rack?
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Old 10-01-2011, 04:21 PM   #19
_cy_ OP
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Quote:
Originally Posted by fishkens View Post
Nice find of a great bike.

I'm curious about the engine case, trans, etc. being painted black at the factory. Is the original owner still around to confirm? Has anyone ever heard of BMW painting the cases black (before the K-bikes)? Just curious.

Any mods other than the rear rack?
no other mods that I'm aware of ... rear rack is the only piece I can find that was added.
unfortunately seller's dad passed away last year.

there's is NO way that engine got painted black without entire motor being out of frame. all indications are this bike has never been apart. factory plastic straps are intact all over bike's frame.

every single picture of any R90S, that I've been able to find or heard of all have silver engine bodies????


_cy_ screwed with this post 10-01-2011 at 04:35 PM
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Old 10-01-2011, 04:42 PM   #20
fishkens
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Originally Posted by _cy_ View Post
there's is NO way that engine got painted black without entire motor being out of frame. all indications are this bike has never been apart. every single picture of any R90S, that I've been able to find or heard of are all silver engine bodies????
Agreed, that's why the black paint is curious. Given that the PO was an EE I imagine he may have had the patience to R&R the engine to paint it and reassemble it perfectly. Or, the engine may have been painted in the frame?

Are the white stripes on the timing cover bare aluminum or painted. Just wondering if that's what the pin striping tool was used for.

Regardless, looking forward to seeing this bike cleaned up and on the road.
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Old 10-01-2011, 05:41 PM   #21
supershaft
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I don't think that engine paint is from the factory. Who knows? It might have been Butler and Smith that did it but I suspect it was done after purchase. Tons of folks had factory zip ties.

I would do first things first. Get a battery and change the oil and filter and start it up and see how it runs. Afterwords I would do a leak down and compression test. Hopefully, the cylinders haven't rusted and pitted.

Next thing I would do is drain the tranny fluid and hope there isn't water in it!

It will be a miracle if the clutch isn't stuck and needs its splines lubed!

Then I would move on to the brakes.

I would cover the big bases first and thusly try to manage where and why the money goes here or there.
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Old 10-01-2011, 05:54 PM   #22
vernon dent
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amazing.
i just got my newly purchased 8100 mile 74 r90s back on the road today. been stored in a basment for six years, two previous owners. serial #4950982, don't know where that puts it in production or u.s. distribution.

i have owned it for two weeks. new tires/tubes, carb clean, master cylinder rebuild, steering stem bearings, fluids changed, wheel bearings repacked, rear brake light switch, clutch cable, air filter, odyssey battery and a few things i can't think of right now. my mechanical ability is nil (as my signature states) so i had a trusted mechanic at a small independent bmw shop do it.
original paint, seat, etc. nice enough not to re-furb. got the original owners manual, tire pump and one correct mirror. plus a box of parts that included air filters, oil filters and other service related parts. no service records, but i think the spares are a good indicator.
like you my initial thought was sell it to buy a more modern mount. but how many chances do you get to own/ride an original r90s? in forty years prior i've had none. heres a couple of pics after its first quick wash today since being stored.



fwiw, i have never seen a r90s or for that matter, a bmw airhead with the engine painted black from the factory. i've owned beau coup /5's, /6's, and /7's along with three gs' and a gspd.
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Old 10-01-2011, 06:01 PM   #23
Renner
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Quote:
Originally Posted by _cy_ View Post
no problems getting premium in US. but I suspect down south, one runs what's available.
If you anticipate running the R90S where the necessary octane isn't available, you may be able to lower the compression using a shim at the cylinder base.
From Snowbum's site at http://bmwmotorcycletech.info/techindex.htm

The stock cylinder base SHIM, during 1970-1975, was 1/2 mm (about .020"), and are not to be used for 1976 and later. For 1976+, TWO SHIMS were available, and these are ONLY for 1976 and later....the so-called Step 1 compression lowering gasket was .7 mm (.028"); and the very low compression gasket was 1.2 mm (.047"). BMW HAS used the word GASKET for these SHIMS. The original part numbers were 11-11-1-257-092 for the /5, for lowering octane requirements. Used on /5 and /6 was the 11-11-1-255-001. Use of the 11-11-1-335-650 base gasket will lower a 9.2 CR to about 8.6.

I think the R90/6 shim would work on your S, and installation/removal isn't terribly difficult.

Is this your first Airhead? Do you subscribe to the Airlist?
There must be an R90S-specific forum somewhere... yahoogroups or similar.

the 'bum has about 25 pages concerning the DellOrtos alone, including links to factory manuals & etc.
You may go blind looking for it, but most of it is there somewhere.
http://bmwmotorcycletech.info/dell.htm
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Old 10-01-2011, 06:05 PM   #24
vernon dent
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over the years i've had a few mega motored japanese four cylinders including a 160+ hp suzuki gs1150/1229 and a 150+hp bandit 1200/1216 both running 11.5:1 compression. none had a problem on 93 octane pump gas.


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vernon dent screwed with this post 10-01-2011 at 06:11 PM
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Old 10-01-2011, 06:13 PM   #25
danedg
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Please don't scream too loud, when you find out you're not this 37 year olds' second date....
Toss the tires and tubes...
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Old 10-02-2011, 08:54 AM   #26
DoktorT
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If you expect to be in situations that only low octane is available, I would lower the compression. Rather than shims, I would install the 9:1 90/6 pistons. You can still do the ton all day long. I would put in a 32/10 rear drive as well to make better use of the modified torque.

With my 9.5 RS, fine tuning is essential to reduce pinging with current premium. I set the mixture at the high end of spec and drop the timing back 2 degrees. Keep the rpms up for highway work and easy on the throttle around town at lower rpms. That works well with current premium, which is at least 2 points lower octane than the premium spec they were designed for and available 30 years ago.

And you cannot compare an 11.5cr jap combustion chamber design to the airhead. Current Porsches have higher cr than the airhead but are designed for lower octane used today.

It is like comparing a wedge head to a hemi head. Apples and oranges.

Make a photo copy of the factory maintenance schedule. Address everything as time allows and cross them off as you go.

Do sign up for the Airheads list. Daily answers to specific question from million mile airheads. Best, find an experienced airhead by joining the ABC group. Some one who has owned several with 30 or more years experience, to help you with hands on inspection and procedures.

Get yourself to an Airheads Barley Therapy. Even if you can't bring the bike, go and watch and ask questions. Sharpest way to kick the learning curve in the butt. If you feed the kitty with 10% of the value received, there will be plenty for Barley water for everyone.
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Old 10-02-2011, 09:20 AM   #27
_cy_ OP
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Location: Tulsa, Oklahoma
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Quote:
Originally Posted by danedg View Post



Please don't scream too loud, when you find out you're not this 37 year olds' second date....
Toss the tires and tubes...
nah .. R90S oxidized condition jives with what a machine would look like after 30 years of being stored in an non air conditioned environment. Summers and winters in Tulsa both can be harsh. there's an old saying in Tulsa... don't like the weather? wait a minute, it'll change...

being in the geographic center of USA. Tulsa gets it on both ends of extremes in temps. there's other details of purchase that I cannot post, that verifies this bike provenance.
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Old 10-02-2011, 09:23 AM   #28
jackd
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Quote:
Originally Posted by DoktorT View Post
If you expect to be in situations that only low octane is available, I would lower the compression. Rather than shims, I would install the 9:1 90/6 pistons. You can still do the ton all day long. I would put in a 32/10 rear drive as well to make better use of the modified torque.

With my 9.5 RS, fine tuning is essential to reduce pinging with current premium. I set the mixture at the high end of spec and drop the timing back 2 degrees. Keep the rpms up for highway work and easy on the throttle around town at lower rpms. That works well with current premium, which is at least 2 points lower octane than the premium spec they were designed for and available 30 years ago.

And you cannot compare an 11.5cr jap combustion chamber design to the airhead. Current Porsches have higher cr than the airhead but are designed for lower octane used today.

It is like comparing a wedge head to a hemi head. Apples and oranges.

Make a photo copy of the factory maintenance schedule. Address everything as time allows and cross them off as you go.

Do sign up for the Airheads list. Daily answers to specific question from million mile airheads. Best, find an experienced airhead by joining the ABC group. Some one who has owned several with 30 or more years experience, to help you with hands on inspection and procedures.

Get yourself to an Airheads Barley Therapy. Even if you can't bring the bike, go and watch and ask questions. Sharpest way to kick the learning curve in the butt. If you feed the kitty with 10% of the value received, there will be plenty for Barley water for everyone.
This is the best advice I've seen yet on how to put this bike back in service. Add to this the greasing of all important areas and fluid change-outs and you should be good to go.
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Old 10-02-2011, 09:38 AM   #29
DoktorT
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Originally Posted by jackd View Post
This is the best advice I've seen yet on how to put this bike back in service. Add to this the greasing of all important areas and fluid change-outs and you should be good to go.
Please do see if you can find any ommissions whatsoever not covered by what I said. "the factory maintenance schedule. Address everything "

All lubes and fluids IS covered by that, and EVERYTHING ELSE. No need to repeat the minutae of that which is already given by the best source available.
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Old 10-02-2011, 09:50 AM   #30
_cy_ OP
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Quote:
Originally Posted by DoktorT View Post
Please do see if you can find any ommissions whatsoever not covered by what I said. "the factory maintenance schedule. Address everything "

All lubes and fluids IS covered by that, and EVERYTHING ELSE. No need to repeat the minutae of that which is already given by the best source available.
thanks... that's exactly what I will do... making a copy of factory maintenance schedule. then using it as a check off list.

under no illusions here ... there is NO way I can hope to be in the same league with folks with 25+ years of Airhead experience. finding out there's tons of technical resources available with a bit of digging. someone made a comments about going blind looking for something on Snowbum's site. I'm going blind after reading some of the voluminous articles on Snowbum's list.
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