74 R75/6, should I buy it?

Hi, I'm mostly a new bike guy with several late model RT's under my belt and a very long riding history on lots of different machines, so I know my way around most bikes. That said I know that there's nothing like owning a bike to know the finer points of what its high and low points are, and what to look out for if you are buying one.

I am going to look at a nice 74 R75/6 this weekend and I was wondering if any owners of this model or period could tell me briefly what to look out for, like rusty tank, engine noises, decomposing rubber, common leaks, non original parts, etc.

Thanks in advance for your help!

R75

Biggest thing to remember on old Airhead's is the rubber condition. A bike that has sat most of it's life will have severe deterrioration of most of it's rubber parts.

Other things to check:
oil and filter maintenance
brake fluid condition (pull the tank and verify condition of fluid). M/C is under the tank)
Fork Fluid maintenance


'74 model trannies have a weak point in the shifter return spring. Maybe find out if it's been updated. BMW had an upgrade kit that was available. The shifter return spring can break, leaving the bike stuck in whatever gear was selected. The upgrade kit is nice as it also has different profiles for the pawl, eliminating false neutrals between 1st, 2nd and 4th and 5th.

Miles? How has the valve clearances held up over time? Rapid clearance loss indicates a problem with valve seat recession. Has there been any need to upgrade the heads to unleaded valves/seats? Clutch?

wipe your finger in the exhaust
look for greasy black
that would indicate the burning of oil
it is an old bike,a hobby
let the price reflect that
unless it has been gone through already

1974 was a transition year. You want to ask if they know of any transmission work that has been done.

+1 on whether the valves have been upgraded for no-lead fuel.

When looking at a oldie, potential purchase, I'd do all the above and then if you can, wash it and detail it out little.
You'll be amazed at what you find then, all the little oil leaks, dings, scratches etc. It can give you a good idea of what you are really looking at.
Your not going to really know what you got for about 6 months anyway, but a wash and dry and detail is a good start to see if you want to even consider it.
I've got a 1978 R80 in overall good- very good condition, but after I owned it for awhile I had to, of course, put some $$ into it.
just my 2 cents.

Thanks all, that is all good info. Bike has 30K miles, which seems low to me. Questions: Are the valve upgrades to a different grade metal on seats and valves? Are seats easily replaceable by me or is that something that needs a good machine shop to bore out and press in new ones? Also, will a ride around the block tell me if the trans is OK or not or is that something that only rears itself on a long ride, after warm up, etc?

After buying so many used cars and bikes over the years I came up with a new maxim for myself. If I think the car/bike is in perfect condition when I buy it that probably means I will be able to tolerate all the defects I didn't know it had.

I should probably get one of those UV flashlights to inspect for leaks.

The bike is probably a long way off from needing valves/seats. All engines that relied on leaded gas will eventually have recession problems...little bits of the seat wear off and stick to the valve face creating the problem. After the debacle of the '81-84 unleaded seats, BMW came out with a proper alloy in the seats that transferred heat back into the head...that was the issue at that time. If/when you decide to do it, just get parts from BMW. I'm no machinist, but I would suggest finding someone who has done BMW heads before. On my /7, I sent my heads to Ted Porter at the Beemershop.

As for the trans, you might find shifting issues right away, but that could just be a clutch cable adjustment. Deeper problems would require a longer ride I think. But again, with only 30K miles and if there's been decent maintenance, the chances for issues are lowered.

The common leaks are the PRT seals, RMS, and neutral switch, all easily addressed but it needs to be reflected in the price. Within the scope of the home wrench for not much money, just a few days labor. Gets pricey if you pay a shop to do it though. I had a nice '75 /6, it needed all of what's been mentioned, including trans work, but was fine after it was sorted out. Good luck.

RPGR90s said:

Biggest thing to remember on old Airhead's is the rubber condition. A bike that has sat most of it's life will have severe deterrioration of most of it's rubber parts.

Other things to check:
oil and filter maintenance
brake fluid condition (pull the tank and verify condition of fluid). M/C is under the tank)
Fork Fluid maintenance


'74 model trannies have a weak point in the shifter return spring. Maybe find out if it's been updated. BMW had an upgrade kit that was available. The shifter return spring can break, leaving the bike stuck in whatever gear was selected. The upgrade kit is nice as it also has different profiles for the pawl, eliminating false neutrals between 1st, 2nd and 4th and 5th.

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Has the bike lived a charmed life and been parked inside? The bell-shaped rubber boot on the transmission end of the speedo cable, when old, can allow moisture to wick down into the works causing mayhem. I once bought back my '76 R90/6 that had been parked/abandoned outside for several years. When I drained the fluid I found the dreaded coffee-coloured water-contaminated gear oil. I would recommend that you be allowed to drain it for inspection as a condition of sale.

Cheers, Russ

You have a good idea of what to look for

Bill, your list of stuff e rusty tank, engine noises, decomposing rubber, common leaks, non original parts). Covers a lot of what to look for, you have a good start on things.

I would say the one thing to look out for is how was the bike stored? Check the liner of the gas tank, if it is not red/brown, it may have been relined. A relined gas tank is only as good as the person who relined it. I have seen pretty tanks on the side that were leaking on the bottom out of sight.

A couple of guys have mentioned transmission fluid and water. My friend at his shop, just rebuilt a transmission that had water in it. Four new gears (they were badly pitted) and new bearings. This on top of a complete engine rebuild. New cylinders, pistons, and a crank because of bad oil and moisture. Oh the bike was pretty to look at but had a lot of problems.

I would also check the wiring of the bike. The factory wiring is very neat and routed fairly simply. If you should find a bundle of wires that don't look neat run away! I had a friend who purchased a Harley Sportster that had been "modified" by the PO. Turns out the PO did not realize the charging system light needed to be in the circuit for the charging system to work properly. I found the problem when I unrolled a large bundle of wiring taped under the headlight.

Wiring harnesses and connections can corrode, or the insulation can break down over time or environment. Check for brittle wires. Loose connections, or improper connections. Non standard wiring terminals crimped on for whatever reason are only as good as the person crimping them, the tools and quality of the connections.

As I have written, you look like you have a good grasp of what to look for. If you buy the bike, let us know how you make out. St.

Price and service records matter a lot!

A lot of what you should pay for a 40 year old very common bike really depends on how much the seller wants and if there are ownership and service records to document a reasonably cared for motorcycle. There are a lot of "Bits A Bikes" out there that are slapped together with spare parts and polished up to make them look good for and represent a long time stored bike when in fact the bike is slapped together with spare parts and advertised as a "it ran when stored" deal.

First off you should verify all the serial numbers match, title, engine block, frame and ID tag. If they don't or there is no title or history of ownership you should rethink what your looking for. If they do dig a little deeper and try and get an ownership and service history on the bike from the seller. There are many issues that can jump up when buying a first year (1974 /6) like brakes, transmission problems and a very expensive main wire harness, if the bike has a sketchy history or the seller doesn't have accurate and verifiable information on the bikes past you should treat it as a parts bike until you can verify its what you want.

As far as what to look for I would start with:

Numbers matching.
Decent service history.
Contact with previous owners.
Check the under tank brake master cylinder for long time leaks.
Bad stuff in drive train oil.
Bent, broken or missing frame tabs and attachment points.
Odometer or speedometer that has been replaced.
Bent or cracked rims and overall condition of the bikes wheels and tires.
Bent main frame, rear sub frame or worn out suspension.

Theres a laundry list of things to look for but it mostly boils down to a trust of the seller and how much your willing to spend on a project.

I'm trying to get the VIN and then call the two local dealers for service history. This has worked in the past for other bikes, but maybe privacy has ratcheted up since then.

The bike looks from the photos like it has lead a charmed garage life. Seat looks original and in good condition, which usually means somebody cared about it, which hopefully extrapolated into the rest of it for care. We'll see...

Looks can be deceiving

With all used vehicles, looks can be deceiving.

I bought a 78 R100RS used from a fellow. The bike was in very nice shape, plastic, seals, chrome, and all looked real good. The only thing wrong was the fairing was damaged from his ex girlfriend knocking it over with her car in a fit of pique. Then the PO dropped it off the side stand to mar the other side. With those repairs made, I had a limited number of sale RS bike with 35K on the odometer.

I rode the heck out of it for two years, got knocked off of it by a car, and the bike spent 14 years in baskets before being put back together again by Glenn at the Beemer Barn.

Now Glenn did nothing to the engine during the rebuild as I told him it ran fine and there was no need to do anything.

Well, it uses oil badly. Upon disassembly to find out why it is using so much out, it turns out the mileage may in fact ben around the horn one or two times. The rings are shot and the pistons in the bike are the biggest set available. Also, the valve guides are very loose.

Do I regret buying the hike now? No, for the most part, I got what I was bargaining for. The price was right at time of purchase.

The lesson learned is looks can be deceiving. Glenn just finished working on another pretty bike that required new cylinders, pistons, connecting rods, timing mechanism, bearings and gears in the transmission. Due to water and neglect. Again, a pretty bike but flawed. St.

If you like to do some wrenching, compared to those R1200RT's you got, the airhead will be very easy to work on, they are so simple.

nickrides said:

If you like to do some wrenching, compared to those R1200RT's you got, the airhead will be very easy to work on, they are so simple.

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Famous last words.