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Talk Me Out of Buying a '77 /7!

art1100

New member
Hello fellow BMW riders,

I just recently joined the BMW family last year when I purchased a 2000RT for my 50th birthday. I've been around bikes for more than half my life and had always wanted a BMW. My RT was a bit of a "rescue"... Previous owner had neglected it and it needed a final drive rebuild so I made my offer accordingly.

Anyway, I have found a 1977 R75/7 about an hour away from me. Current owner has owned it for about 5 years and current mileage is only 27k. Seller's ad mentions several maintenance items recently done such as rear main seal,oil pump o ring,clutch spring,clutch plate,flywheel bolts,input and output shaft seals & splines lubed. Asking price is $3900.

I'm planning on taking a look at the bike tomorrow afternoon. Anything I should be aware of?? Am I crazy for even considering a bike that's only 8 years younger than me?? :scratch

Regards,
Art
 
Art -

The '77 R75/7 is a one year bike...the next year it was an 800cc engine. I think the slight rarity makes it cool...I don't think parts would really be an issue though. And 1977 was the best year in terms of engine performance...beginning with the '78 models, and likely in January 1, 1978, the engines were "detuned" in advance of new EPA standards.

One thing not mentioned was anything associated with the top end, but with 27K miles, issues of valve recession are probably a long way off. Price doesn't sound too bad.

Sorry, but I can't talk you out of it!
 
My Experience with R75/7

Hello, my first BMW was a 77. R75/7 I loved it. I only got rid of it when I moved up to a 83 R80RT.

FYI, I switched to the RT not because the /7 was a problem bike it was not. I switched because I wanted something with a fairing and fairings available to fit the /7 were not as pretty nor well designed as the stock fairing on the RT. Also with the RT I got twice the stopping power in the front with two disc brakes. I also got an upgraded trouble free ignition system. If I had been able to find a fairing as well designed and pretty as the RT. I would still have the /7. I have had an 84 R80RT new since 85 when I wrecked my 83 R80RT on a deer.

If I didn't have a 78R100RS, along with a small bank account, I would probably look for a R75/7 for a naked bike. Two bikes keep me busy and the wife would kick me out of the house if I brought home a third.

OKAY, so I have gushed positive about my experience. Not much of talking you out of buying.

The 77 R75/7 I believe only lasted one year before being bumped up to the R80/7. I am not sure how available parts are for this specific bike. I know from a recent problem with my 78 RS, I needed a headlight/horn switch, only to find out they are NLA. Parts are available either from BMW or aftermarket vendors, some are NLA. I don't believe you would have problems finding maintenance parts oil filters, filters and the like. This is something you should take into consideration when buying the bike.

The only other problem I had with my 77 R75/7 was the points in the ignition system would constantly need adjustment. On my 78 RS, I installed a Boyer system. The R80RT had electronic pointless, and lasted nearly 178K miles before I changed anything on it. I don't ride the 78 much to say how I feel about the Boyer system.

Understand, the R75/7 probably only puts out 45 to 50 HP. I have not ridden a 2000RT but I will bet it gets up and goes a bit better than the R75. As for me, my 55 HP R80RT is powerful enough to get high speed driving awards if I am not careful. I do wish it had more guts in the passing power.

Don't know if this helps, Cheery Bye. St.
 
Thanks for the replies. I wasn't aware of the '77 being somewhat an odd bird but I do have an excellent source for used BMW parts close by. I live about 25 minutes from Re-Psycle BMW in Lithopolis, OH. Maybe I should give them a call and inquire about parts availability??

I'm not especially concerned about power output on the /7. It's a 43 year old, 750cc twin so I'm not having any great expectations there. If I were to get it, it would be my "sunny Sunday" bike and probably be handed down to my son. :)

Cheers!
Art
 
Art -

The '77 R75/7 is a one year bike...the next year it was an 800cc engine. I think the slight rarity makes it cool...I don't think parts would really be an issue though. And 1977 was the best year in terms of engine performance...beginning with the '78 models, and likely in January 1, 1978, the engines were "detuned" in advance of new EPA standards.

One thing not mentioned was anything associated with the top end, but with 27K miles, issues of valve recession are probably a long way off. Price doesn't sound too bad.

Sorry, but I can't talk you out of it!

Can you elaborate more about this valve recession?? Sorry, I'm a complete noob when it comes to Airheads. I spent about 6 months researching Oilheads before I bought my RT. This Airhead bug is kind of spur of the moment! LoL

Cheers!
Art
 
I really think the issue with parts would be pretty limited. Now if it were an R65, there's lots different on that series of bikes. But for things that really matter, the '77 model is going to have the same frame, transmission, clutch parts, wheels, etc., etc., than other bikes of the same era. The crankshaft and camshaft are probably the same...just different pistons. Seat is the same...same single disk ATE brake up front, same rear brake. OK, the engine badge is different, so would the battery side cover. The '77 would have been a mechanical tachometer whereas the '78 models came out with electronic tach.

I don't really think that should be a deciding factor.
 
The valve seat recession issue came up as leaded gasoline was phased out. Oak wrote extensively about this in the BMW News at the time. There were a couple of iterations of valve seat materials tried until BMW got it right.
 
The issue with valves is a nuanced thing, as Oak wrote. Valve recession was the standard thing that all flat tappet engines experienced during the '60/70s. That was when the valve seat material sloughed off the seat and ended upon on the valve face. And this was due to the disappearance of lead in the gas. From 1981 to 1985, BMW tried changing the valve seat to a different material. Unfortunately, the material didn't not conduct heat well which is one of the jobs of the seat...transfer heat from the valve to the seat and into the head. Since the heat wasn't transferring, the valve face would get very hot and warp or tulip...Oak called it valve face plastic deformation. The result was the same as recession...the valve clearances would close up over time. BMW finally fixed the problem with proper valve seats and valves beginning with the 1985 models.
 
Okay, thanks for the clarification on the valve seats. So am I correct in assuming that if I'm planning on putting a decent amount of miles on this bike, I'll need to have some work done on the heads eventually??
 
Eventually...but could be a while. You'll have plenty of warning as you will begin to notice that the valve clearances close up after 500-1000 miles. The problem seemed to be worse on the 1000cc bikes due to more engine heat...and even worse for the RT/RS bikes with the fairing. So the 750cc bike could go a long while before any issues. You never know, but odds are you would be fine for a long time. I wouldn't pull the heads for this work just because, but would consider doing the heads if the engine was down for some other reason.
 
Buy it

With any USED bike you never know what you are getting unless you know its history form day one. Kurt has filled in some gaps and done a wonder with his answers, As well as Swall. I would not worry about valve recession on this bike.

Take a good look at the electrical switch gear. Make sure the headlight/horn/kill/turn signal switches work. THEY may be NLA if they don't. To be honest, I have not looked up those parts but found the switch for my RS is NLA. For the most part, stuff you need to keep the bike on the road is available at Recycle or any dealer plus, lots of other shops such as Siebenrock.

I would never had sold my R75/7 if it were not for the fairing issue. Of course, I could have done like my dealer at the time did, he mounted a R100RT fairing onto his R90S bike. Problem with that was, the work involved would have cost me as much as trading in the R75 and buying an R80RT. His R90S had dual discs on the front the R75 did not.



I would buy the R75, and ride it. If the wife would let me have it, I would buy it myself. I love my R80RT, a very smooth engine. The R75 I think was a bit peppier, and had a little more oomph. I can't remember very well, it has been a bit of time since I last rode one.

I do remember it having a mechanical tachometer. The needle fell off and a friend of mine with steady fingers glued it back on. It was a pretty burnt orange color. Very pretty. I bought it from my future brother in law. He worked at a salt mine and the crome on some of the parts needed redone. He bought an AMF Harley, I got the far better deal. LOL. The Harley was a true AMF POS. Cheers, St.
 
Boy, the OP sure came to the wrong place if he was hoping to get "talked out of buying a 1977 /7"!

I have a 1977 R100RS (first year!). I purchased it quite inexpensively ($1400) from a dealer that took it from someone who's husband had passed. The dealer didn't even know if the bike would run. I saw the bike on the floor and started mentally adding up the things that I thought would be needed. I first asked about the price. One of the sales guys said $2800 (this was in 2002).

I turned to walk away. The manager came running out of his office and said that I could have the bike "as is" for $1400. I said ok, can you trailer it home for me? They said that they would (I lived about 7 miles distant from the dealer). My next question was did the bike run? They didn't know. So we checked the oil, added a bit, then added a bit of gas to the tank. We moved the bike outside and Vroom, the bike started! I rode the bike around the parking lot to check the brakes and shifting. The important stuff worked. A 30 day temporary tag was added, I did the paperwork and paid. I rode the bike home and later came back for the bike I'd ridden over to the dealership.

That was the last 7 miles the bike traveled for the next 2 years. I took everything apart. When I drained the transmission oil, a fingernail sized piece of metal came out. [This is NOT a good sign!!!!]. I corresponded with Oak (a now deceased airhead guru). He indicated that the transmission needed to come apart for a re-build. At the time he was still working on bikes and said that I could send it to him. Instead I decided to learn more about BMW transmissions and do it myself.

At the time I lived fairly proximate to Re-Psycle BMW in Ohio. I relied heavily on them for parts, new and used, and a lot of advice. They had several /7 bikes and RS bikes that I could use to study for assembly, e.g. wire routing.

When I first got the bike home I took a photo and that picture was on my laptop as a background. I was on a trip for work shortly afterwards and a fellow sitting behind me asked if that was a 77RS. I affirmed that it was. He became very animated and began telling me about the /7s and the RS in particular. His enthusiasm transferred to me. The finish on the bike was rough. As part of my re-do I decided to have the damage repaired and repainted with correct pinstriping. I checked with Holt BMW who has a reputation for very good work, but not inexpensive; their estimate was over $2200. Instead I went with a local Harley custom builder. The owner of that shop became interested in the RS and did research on the bike so as to get the pinstriping correct. His cost estimate was $1000 to $1500. I asked him to do it for the higher number and take his time; he wished more customers were like me.

I obtained stainless exhaust headers and mufflers from EPCO, now out of business. I rode over to EPCO's facilities (a barn behind Tom Epperson's house) near Dayton and had nice conversation and obtained the mufflers and headers.

In 2004 the AMA Vintage Days at the Mid-Ohio race track featured BMW. There was a fellow there with a nicely done 77 RS. That really gave the encouragement to finish putting mine back together.

I met a feller with whom I've gone to many rallys because he wanted to purchase my 77RS. I declined and he subsequently obtained his own. Both of us noticed valve recession (and my bike was consuming oil, about half a quart in 600 miles). We both ended up sending our heads to Ted Porter's Beemershop for re-work. The re-work for me included hardened exhaust valve seats, new valves, new valve seals, and new valve springs. The heads were so clean and new looking I wondered it these were same ones that I sent in; Ted said that they were. I actually knew this due to some specific marks made prior to sending the heads in.

I also obtained the nickasil lined cylinders, pistons, and rings from Ted Porter. No more oil consumption.

In 2017 my buddy and I met up (I'd since moved to NC) and we went to the 40th anniversary of the RS. We met the bike's designer, Hans Muth. Hans signed the rear fenders of our (and many other) bikes. I am happy with my 77 /7.

Much of the decision to purchase a bike comes from your expectations and desires. If you don't mind working on a bike and even enjoy the process then an airhead might be right for you. [You should also consider joining the Airheads Beemer Club - airheads.org] Most new parts can still be obtained; you do understand that BMW stands for "bring more wampum"? Places like Re-Psycle BMW can provide good used parts at substantial cost savings and there are still some gurus around to answer questions. Shops like Ted Porter's Beemershop can do a good, reliable job in repairing the heads. There is a place, Boxer2Valve, in NC that I've yet to visit, but they have posted many useful YouTube videos.

Good Luck with your decision and post some photos when you get the bike. Beware of looking at Brook Reams' airhead restoration webpages and forum pages. He sets a pretty high water mark!
 
77 r75/7

R75/7 was my first airhead having owned and rebuilt 4 others I can say I cannot comment on the price that's all about condition and with no pictures the price could be all over the place. Not the lowest price and pushing the higher limits. The one thing I can say it is arguably the smoothest Airhead ever made and for that alone I wish I still had mine and have been keeping an eye out to see if I can find another. Let us know what you find and if you decide to jump into it. POST PICS!

Roy
 
The R75/7 was a one-year model, but the 750cc engine had been around, with few changes, since 1970. The /7 bikes differed from the /6s only in some of the frame details, the fuel tank design, and, perhaps, the handlebar switchgear. There may be an issue with the ‘77’s compression ratio—it may be high enough that you’ll need to think about reducing it through cylinder base gasket installation or dual-plugging, to prevent pinging with currently-available fuels. But the engine will be ridiculously smooth; the crankshaft, which was the same one used in the 600, 900, and 1000cc engines, had counterweights that were optimized for the 750 and 800cc engines. Buy it.
 
brakes

I assume that the /7 still had single ATE brakes? They were anti lock by design, at least they were on my 74 and 75 /6 bikes. When my underseat mc spilled its guts on the garage floor, I replaced with a Magura handlebar mc. It is somewhat better, but definitely not enough, now if your bike has dual disc brakes it may be a different story.
 
Trade up

One of the reasons I traded my R75/7 in for a 83 R80RT was the brakes.

The R75/7 had only one ATE disc brake on the front. Adding weight and a passenger, pushed the system to the limit. For a Naked R75, the ATE system was adequate with a solo rider. The dual Brembo system on the RT is far better.

I ride my 78 R100RS and always think about doing a front end swap to a dual Brembo fork and brake system. The only thing stopping me is the lack of used parts and cash. Everyone seems to be swapping the ATE systems out for Brembo as such, Brembo front ends are kind of hard to find for a reasonable price. There are lots of dual ATE systems on the web.

I can't say much about how much difference there would be between the handle bar mounted master cylinder versus the under tank system I don't think I will be going that far as I don't want to change switch gear. I can say for certain the Brembo brakes are far superior to the ATE brakes.

Oh, here I go launching a new thread off the subject of the thread in hand, LOL. St.
 
It is my carefully considered opinion that the 1977 model 750 engine was the best Airhead engine BMW ever built (excluding of course some of Pridmore's race engines :) ). It is also my carefully considered opinion that the ATE horseshoe caliper single disk brakes were (even when properly adjusted) the worst brakes they ever built. :banghead Even with the aftermarket Meehanite (cast iron) disk and Ferodo pads the brakes were marginal. But still better than dragging your feet. :)
 
A bit off track here, but I don't get the disdain thrown at the single ATE brake. I happen to like mine a lot...probably because I've never really had anything else. I kind of agree about the meekness of the brake up until my last rebuild. I had to redo the under tank master cylinder...honed it and basically put new OEM stuff back in. I always had trouble getting the eccentric to align. I read a trick and gave it a try. I put some pressure on the brake lever and held it down with a bungee/rope. I then rotated the eccentric and could feel it go tight each direction as it worked against the pads. I could feel the center of that was the sweet spot. I locked it down, continued the bleeding process.

The brakes feel the best they ever have. I get easy, firm 2-finger braking and they really work great. It's a progressive feel and it really seems to haul down the front end. I think getting that eccentric perfect did the trick.

Back to the sales pitch for the '77 /7! :wave
 
I use to own a 64 Triumph Bonneville that had drum brakes front and rear. They worked great.... if one used "plan ahead" stopping. I owned a 75 R60/6 with drum brakes front and rear, these worked better than the Triumph's brakes. I think that disc brakes are better than drum brakes. Some folks can make do with either. (Following is from some old BMW ad - )

Fred_1-vi.jpgFredSmiles-vi.jpg
 
It is my carefully considered opinion that the 1977 model 750 engine was the best Airhead engine BMW ever built (excluding of course some of Pridmore's race engines :) ). It is also my carefully considered opinion that the ATE horseshoe caliper single disk brakes were (even when properly adjusted) the worst brakes they ever built. :banghead Even with the aftermarket Meehanite (cast iron) disk and Ferodo pads the brakes were marginal. But still better than dragging your feet. :)

Yes, that's a fact indeed! I rode the bike yesterday and soon discovered you have to gauge your stopping distances with binoculars! LoL Engine was a gem but the handling was off on this bike.E Either the vintage style (but only 5 years old) Dunlops or perhaps the steering bearings were in need of adjustment? I decided to pass on the bike for now and perhaps spend more time learning about Airheads before taking the plunge. Afterall, I'm still in the process of doing upgrades to my Oilhead that I bought last June.

Cheers!
Art
 
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