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tete 08-27-2012 02:56 AM

Back on an Airhead - 1975 BMW R90/6
So after owning a 81 R65 a few years back, and 4 hondas in between i got my hands on a 1975 R90/6 Monza Blue. I got what I believe is a smoking deal, but of course it was sitting for a bit and will require the usual paces to get her going. It was parked in 2001 gue to a faulty starter. Im sure the battery is rubbish. It was stored in a garage here in Az. The tires are surprisingly good still and it was leaking oil at some spots which is to be expected since it hasnt moved for a decade ( very little oil ).

I hooked up some juice to it and all the lights etc worked. Im chargin the battery overnight to see if there is anything left to give simply for testing.

The bike came with alot of exta stuff.
new seat pan off what looks to be off an RS model - very cafe like.
a larger capacity tank
A fairing - bullet like - not the big cobra kind.
new mirrors
some shocks that look to be off a higher RS model
Also fender both front and back.

Im pretty excited about getting it going. so here a few things that I'm concerned about first.

What is general " process for bring a bike from state of storage - ten years sitting.

This is my initial plan:

Change engine oil, plugs -
rebuild clean carbs -
find a starter - which is a good brand? Im on a budget because I just had my 3rd boy. Diapers take priority
also souce a new Gel battery as if I recall my R65 would use up alot of juice.

please if you have nay advice you WANT to give me please do. Till then I will use the search function and learn as much as I can about my new bike.

disston 08-27-2012 08:31 AM

Before you condemn the starter put the fresh battery in it and clean all the wiring. See how much juice is getting to the starter through the relay.

The '75 models were the 8 tooth verity of the Bosch starter. In '77 they went with 9 tooth. The two don't mix. Your starter matches the gear teeth on the flywheel. So if you go with another starter it has to be 8 teeth. But there is the option of rebuilding that starter and to my mind the way to go. Rebuild parts are readily available or you could have it done for you at an Old Timey Auto Electric Shop. They are getting harder to find but do still exist. And if you are handy at all you can do the rebuild yourself.

I say rebuild parts are available. If the suspect starter has any major defect like a bad rotor or stator or coils or what ever it gets more complicated.

So then more modern starters are available.

Find any number of battery threads in the last two weeks. I think AGM batteries are popular. Maybe somebody will mention a particular one. You can make a smaller battery fit. The 22 AH UB12220 works for some. The stock BMW battery is very expensive again. I think this year around $129 over the counter. The battery in your bike is the wet cell OEM battery.

The rest of your plan sounds good. Rinse the gas tank out well and clean the petcocks. Replace the fuel line. Even if it looks good right now it is going to start leaking almost immediately.

The stock attachment for the battery covers, those triangular things on the side, are a rubber band. It will break and you will loose the right side battery cover. They are hard to come by cheap. If all you have holding those covers on is the rubber band then put the right cover, the left one won't fall off, in the house until you make a more secure attachment, usually drilling a hole and wire tying it to the frame.

Some riders like that color.

Welcome to the Asylum.

I ride a 1975 R90/6 Black

ps, there area of the engine block right behind the front cover is the timing cover. About two inches wide. It looks chrome plated in the picture. Is it just polished? Then somebody did a timing chain on this bike?

tete 08-27-2012 09:31 AM

Thanks for all the info!

First bit is to get a good battery. Perhaps a decent but inexpensive battery and a tender is the way to go.

I have been tryin to use the search function to find what process to go thru in regarding oils. It's is my understanding, that these bike need oil in several spots. or as many as five? I hope that perhaps its some the the wiring of the starter as I read that goes bad pretty quickly, but it is my impression that the PO was pretty well informed with the bike. He's dead now, unfortunately, and his son, had no idea what he was even looking at.

He also mentioned an alternator? I don't think he had a clue but maybe Im really the fool.

The motor does have a chrome / polished strip. You mentioned a chain, perhaps you can be a bit more specific if you don't mind.

and finally, where can I source a OEM seat cover or a company that makes a high quality replica.

In some ways all the information here is a double edge sword as when using the search you end up with so many opinions that it makes it difficult to determine what is good and what is not. Im sure this post isn't helping any. :shog

Horsehockey 08-27-2012 10:14 AM

What Disston said (above). How many miles on this bike? A couple points: I ride a 75 and mine was sitting for a long time too. You've mentioned that budget is an issue. With that in mind, forget about the cosmetics (i.e. seat cover) and begin the two year process of bringing this bike back to roadworthy. A new battery is a good start, and should last at least five years. Some basics: do not remove the front cover of the engine (where the alternator hides) without disconnecting the battery ground cable first. You will likely cause $$ damage to your diode board if you do. Put the bike in neutral and then on the center stand (maybe elevated with 2x4's) such that you can rotate the rear wheel in neutral. Listen for bad sounds at the transmission when you do this. Bad sounds are gravelly dry bearing sounds or "notchiness" while rotating. Sometimes bikes that sit for too long suffer bearing entropy. If crunchy sounds are heard, start saving up for a tranny rebuild (about $600 more). Before you start changing fluids, go buy a set of BMW crush washers for all the fill and drain plugs....then use new ones every time. Guys end up with stripped plug threads when they ignore this. Be patient. In a year or two you'll have a great reliable rider. Until then, all bets are off.

Cordless 08-27-2012 10:18 AM

You might also check in with the AZ Airhead club. I know there is one because we in NM have arranged some campouts together. The airheads would help you get your BMW running without replacing unncecssary parts.

I am running a NM Airheads tech day in my shop next Saturday if you feel like making a trip. BTW, I have a Monza blue '75 R90/6 and so does another of the NM Airheads.

tete 08-27-2012 10:37 AM

A little more info on the bike: It was parked in 2001 has 95,000 miles.

The bike was stored indoors the entire time.

My understanding is the bike ran flawless before the starter issue. The PO had plans to make this into a cafe bike so he opted to start the process before putting in a starter. This is all hearsay so I'll take as worth noting but I certainly wouldn't put money on it.

The tires look very good.

disston 08-27-2012 10:40 AM


Originally Posted by tete (Post 19455969)
Thanks for all the info!

The motor does have a chrome / polished strip. You mentioned a chain, perhaps you can be a bit more specific if you don't mind.

The cover on the front of the engine is the "front cover". Inside this you will find the ignition points, manual advance, alternator and diode board. As mentioned by Mr. HH do not remove the front cover with out first disconnecting the battery ground strap. If the battery is hooked up and the front cover contacts the wrong part of the diode board there will be expensive sparking. Remember: Anytime the front cover is removed or replaced the battery is disconnected.

Behind the front cover is the "timing cover". It covers the timing chain. Do not try to remove the timing cover for any reason until you have been instructed to do so by somebody who knows what is what.

You're learning.

You need a manual. You need at least one manual to begin with, there are three commonly available. One or two manuals may have come with the bike. Which manuals do you have?

Horsehockey 08-27-2012 10:40 AM


Originally Posted by Cordless (Post 19456303)
You might also check in with the AZ Airhead club. I know there is one because we in NM have arranged some campouts together. The airheads would help you get your BMW running without replacing unncecssary parts.

I am running a NM Airheads tech day in my shop next Saturday if you feel like making a trip. BTW, I have a Monza blue '75 R90/6 and so does another of the NM Airheads.

This is excellent advice. ABQ is prolly too far away for a tech session, but I would work hard to connect with the AZ membership. The R65 that you owned before is certainly similar, but has enough differences that you would benefit from learning from others. Aside from the fun, attending a tech session with a bunch of airheads can save you lots of money in the long run.

tete 08-27-2012 10:50 AM

A little background.

I've owned a 1981 R65 but it was pretty clean - replace the float in the carb. that was all.
since then I have had -
2 honda Cb200
1 Cb125

and 2 CB500. 1 that I still own and am selling to help fund this project. If it sales soon then I''ll have some money to put into this rather quickly.

Here is a pic of the CB125 I just finished and sold.

and a pic of my CB500 I am selling.

I rebuilt the carbs in the CB500 and in the CB125s - and little things here in there. Cosmetic stuff is generally cheap and something I am comfortable doing. Also keep moral high while. On the mechanical side I am ok with following instructions but I don't have an indoor workstation so things are not as tranquil. I would say I'm novice mechanic as I have never taken the head off a bike and re-assembled it.

Thanks for all you help. I am going to post more pics of the bike perhaps you guys can point out some of the good and bad just from the pics.

Thanks again.

Horsehockey 08-27-2012 10:56 AM

It would be handy if you can find a receipt for a timing chain replacement. Some guru's recommend replacement every 50K miles or so. In any event, if your bike has 95K miles on it, a timing chain job is in your future. Don't stress out, the bike just runs a little less smooth as the chain starts eating aluminum.

Meanwhile, I don't want to pry and ask what you paid for the bike, but if you didn't pay a ton and if you got a large tank (6 gallon with knee pads) and got an authentic BMW S fairing with it, then you may have gotten off to a very fine start.

tete 08-27-2012 11:07 AM

I will look into joining AZairheads right away. The tach is either broken or turned for some reason. I'm sure the gauges will require a rebuild as well but that can wait.

In the meantime here are pics of the bike via cell phone

disston 08-27-2012 11:25 AM

You have the stock R90/6 carbs, 64/32/11 & 12.

The handle bar mounted master cylinder is a very nice updated part. Makes for better brakes.

Later model valve covers. they are quieter than the peanut style covers. At least the OP didn't chrome plate them. Like he did several other places on the bike.

Good Luck with it. Get a manual.

Bill Harris 08-27-2012 11:26 AM

Nice find. Welcome (back) to the Asylum.


The tires look very good.
Still, they are around a dozen years old and although the tread looks good, the tires may be dry-rotted. Although you are on a budget, don'r skimp on the tires. An orphan is an awful thing to be... :cry

Even though it may be "due" for a timing chain, they can rattle for a LONG time and I've never heard of a timing chain failing. Put it on your "to-do" list of things to look at when time/budget catch up. And yes, if you can hook up with some AZ Airheads, a quick look and listen can tell a lot.

You'll have plenty of time for the bike. Mine has been with me through a career, a divorce, retirement and lord knows what else and it's still a good ride.

Horsehockey 08-27-2012 01:20 PM

From the looks of your Hondas, you've got very good taste. The prior owner(s) of your airhead don't necessarily fall into that category. Most guys, like me for example, aren't really into the chrome effect on the original aluminum patina. What you ultimately do with the airhead is up to you, but you're off to an intriguing start. Looks like you've got an OEM S fairing. If it ain't cracked up too bad, it'll restore beautifully with a paint job. Especially handy if the mounting hardware is in the box somewhere. All very pricey if bought new. The immediate challenge is getting the basics - good electrical, good fluids, good rubber. Shelf life for tire rubber is about six years, then your safety is at risk, as Bill suggested above. Your tach is obviously fubared for the moment. Requires disassembly to put the two little screws back into the face which is a home project, but you may have to farm out the repair if the guts don't work anymore (as indicated by the spun needle). Budget? I think about $200 for shop work. As I mentioned earlier, these re-hab jobs take time and money, but once they're sorted out, they'll give you another 100K miles without substantial additional investment. At least that's the story that's worked with my wife so far.

Biebs 08-27-2012 02:51 PM

Battery - seat cover
Odessey PC680 battery - takes 1/2 the space as stock fits very easy. Seat cover available on Ebay $59 made to fit stock seat.

I had the PC680 in my 74 R75/6 4years + never charge works great fits without messing with the subframe terminals match up.

Also check mottard-eletric new wires for battery+ and _ plus the beacon 1 LED brake light kit. All money welll spent.


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