1971 R75/5 SWB- to lengthen or not?

[VIEJO]

I am the proud new owner (3rd) of a 1971 R75/5 SWB; prior to this the oldest BMW in my garage was a 1976 R90/6. While this won't be the first time I have ridden a SWB /5 it will be the first time I will be riding one on a fairly/hopefully regular basis. I love the nimbleness of the SWB chassis but I'm forever hearing horror stories (mostly from people who heard them from "someone else") about SWB induced high speed wobbles. When I question the incidents further it always seems the bike had a significant amount of added weight over or behind the rear axle and/or was being ridden/pushed to the limit. Now, I don't believe there has ever been a BMW motorcycle manufactured that didn't ride and handle better with a bit of extra weight added behind the rider, but a little common sense needs to be applied here, especially when you start adding weight behind the rear axle and effectively levering weight off the front axle. BMW test riders did note handling problems with the SWB /5 but only under extreme riding/braking conditions, and after the '71 model year BMW fitted the R75 with an extended wheelbase.

My hope is to keep this bike in its original condition, SWB with a four speed tranny, and ride it in a sensible manner (I have a perfectly serviceable '03 K1200RS in the garage to handle any adrenaline needs that might arise from time to time).

I would be interested in hearing "first hand" opinions regarding the decision to either keep the bike as a SWB or go to the lengthened option... at which point I would probably add a five speed tranny as well.

Thanks,

Dave

 

[20774]

No first hand experience, but if it were me I'd keep it as is and get to know the bike. Get it tweaked as needed for the suspension, steering stem, rubber/tires, etc. Probably will surprise you. Then if down the road it's not working out, make the change. Maybe even keep the parts for the SWB so a future owner could swap back if desired. YMMV!

 

[6322]

My ‘71 R75 was one of the nicest riding, handling bikes I’ve had. Everything was box stock suspensionwise, and torqued and adjusted to factory specs (axles, suspension, steering head and swing arm). The correct fork oil, both weight and volume. It rode like it was on rails, light and nimble as you mentioned. Never had any issue with a wobble and rode it past the ton regularly. Just a great bike. The only mods I did were dual plugs, Dyna III, ‘S’ bars and bar end mirrors.

I wouldn’t change a thing on your bike. Just dial it in and enjoy it.

 

[daz]

Keep it and ride it. Enjoy! No problems with my 1971 R50/5.

 

[stevenrankin]

Handling

BMW did a good job with the bike.

Personally, I have found most handling problems people complain about are due to poor maintenance or worn parts not the design of the bike itself. I have listened to a lot of woeful tails of poor handling bikes only to draw the conclusion the problem is the owner not the bike. Most of the time, the owner neglects something or rides above their skill level.

Spend time on getting things in proper order as suggested and I think you will find it is a great bike. Have fun, St.

 

[crouthier]

I've had two SWB R75/5s (including my current '72 SWB) - and while I don't drive crazy fast, it is always stable, smooth and a joy. I had Koni rear shocks on both bikes and they are great. I also try to keep my saddle bags equally loaded...it's a great bike. c

 

[pglaves]

I only had an issue with wobble on a short frame /5 once and it was actually funny. Voni was riding her R65 and I was riding an R60/5 back in 1985. We were in Colorado on a two-lane highway that was following and intermittently crossing a small river. At most such crossings there was what was called a fishing access. At a stop I told Voni that the next time we got to one of those I wanted to stop and have a cup of coffee. So the next one I saw I turned downhill into the parking area among the trees on the river bank. I had just swung my leg over to get off when zoom - down the highway, past the fishing access she went.

At this point she thought I was ahead of her and was trying to catch me, and I was behind her trying to catch her. I had camping gear rather haphazardly strapped on the rear of the bike. Somewhere about 80 or 85 mph the /5 started to wobble. It wasn't really violent so backing off corrected things but I couldn't go fast enough to catch her while she was trying to catch me.

Eventually she just stopped, figuring I would eventually wake up and come back to find her. She was surprised when I came zooming up from behind her. After I got chewed out we had a good laugh.

 

[cwroady]

Love the handling on my '73 75/5 SWB (lengthened swingarm was mid-year '73 model). I've never had the problem and I wouldn't change it to a LWB.

 

[bluehole]

Over 58,000 miles on 1972 SWB R75/5 and I have never experienced a wobble. However, I seldom run the motorcycle over 75 mph. I agree with others. Set the Airhead up the way you like it and put it through the paces. I doubt you encounter a wobble, but if stability is a problem, you can go ahead and make changes then.

 

[daveslash5]

With my SWB 1972 R75/5, which I've had since 2000, I have only experienced handling issues early on when I installed a handlebar mounted windshield on it. Several times when I was turning it went into a wobble that progressed to a tankslapper. The windshield came off and there were no more problems.

I hear that frame mounted fairings work better, but I just use it as a naked bike.

 

[stevenrankin]

Handlebar Windshields

I put a handlebar mounted windshield on my 77 R75/7, The longer wheel base didn't help the least in the handling problems I encountered with it on the bike. Somethings just don't work the way they say they will. Never again will I install a handlebar windshield unless it comes direct from BMW.

Adding a windshield or overloading or improper maintenance are all owner induced problems, not design problems.

It would be interesting to talk to one of the test riders involved with the design of the 71 R75/5 SWB to get their opinion of the bike. I bet they rode them a lot harder than most of us will. St.

 

[22600]

Keep it

My first BMW was a '71 SWB ( I think, it's hard to remember) that I had back in the 70's and 80's. I have said many times that I wished I had kept it. The best, easiest to work on that I ever had. I did have to put in a new clutch back in the late 70's 's just before a trip to Mexico. Did all the work on my front porch in one day and left for Mexico with my wife the next day. We put about 3000 miles on that trip without any problems and never experienced any wobble. I have to say I never rode it over75 mph but always had it loaded down on trips. It had a full faring, leather bags and tail rack always stacked high with gear on trips. I did have the center stand let loose and drop down while on a asphalt road while doing about 70 mph; sounded pretty scary at the time; thought my engine came apart.

I would keep it as it is and never sell it; it's one of the best bikes ever made in my humble but prejudiced opinion.

 

[22600]

That is a beautiful bike

My ‘71 R75 was one of the nicest riding, handling bikes I’ve had. Everything was box stock suspensionwise, and torqued and adjusted to factory specs (axles, suspension, steering head and swing arm). The correct fork oil, both weight and volume. It rode like it was on rails, light and nimble as you mentioned. Never had any issue with a wobble and rode it past the ton regularly. Just a great bike. The only mods I did were dual plugs, Dyna III, ‘S’ bars and bar end mirrors.

I wouldn’t change a thing on your bike. Just dial it in and enjoy it.

View attachment 84984

__________________________________________________________________

Beautiful, makes me want one again.

 

[VIEJO]

With my SWB 1972 R75/5, which I've had since 2000, I have only experienced handling issues early on when I installed a handlebar mounted windshield on it. Several times when I was turning it went into a wobble that progressed to a tankslapper. The windshield came off and there were no more problems.

I hear that frame mounted fairings work better, but I just use it as a naked bike.

Handlebar mounted windshields/fairings don't belong on ANY motorcycle.

 

[VIEJO]

I put a handlebar mounted windshield on my 77 R75/7, The longer wheel base didn't help the least in the handling problems I encountered with it on the bike. Somethings just don't work the way they say they will. Never again will I install a handlebar windshield unless it comes direct from BMW.

Adding a windshield or overloading or improper maintenance are all owner induced problems, not design problems.

It would be interesting to talk to one of the test riders involved with the design of the 71 R75/5 SWB to get their opinion of the bike. I bet they rode them a lot harder than most of us will. St.

According to several of the accounts I have read it was in fact the BMW test riders who confirmed the handling issues with the SWB /5's (which ultimately led to BMW lengthening the swingarm) but they also noted that the problems only occurred under extreme conditions or with the machine overloaded with weight aft of the rear axle.

 

[VIEJO]

R75/5 SWB- to lengthen or not?

Mil gracias to everyone who responded to my OP..... you all confirmed my original intentions for the bike- don't change nuttin' but the oil! Dave

 

[VIEJO]

My first BMW was a '71 SWB ( I think, it's hard to remember) that I had back in the 70's and 80's. I have said many times that I wished I had kept it. The best, easiest to work on that I ever had. I did have to put in a new clutch back in the late 70's 's just before a trip to Mexico. Did all the work on my front porch in one day and left for Mexico with my wife the next day. We put about 3000 miles on that trip without any problems and never experienced any wobble. I have to say I never rode it over75 mph but always had it loaded down on trips. It had a full faring, leather bags and tail rack always stacked high with gear on trips. I did have the center stand let loose and drop down while on a asphalt road while doing about 70 mph; sounded pretty scary at the time; thought my engine came apart.

I would keep it as it is and never sell it; it's one of the best bikes ever made in my humble but prejudiced opinion.

very serendipitous indeed..... I have a place in Utopia, TX, not far from New Braunfels (by Texas reckoning) and I used to live in Taipei ('58-'61) and often traveled to Taichung and Tainan for Boy Scout outings including the incredible Silver Trail from Taichung over the mountains on foot to Hualien.
One of my favorite places, although I probably wouldn't recognize it now.

 

[VIEJO]

My ‘71 R75 was one of the nicest riding, handling bikes I’ve had. Everything was box stock suspensionwise, and torqued and adjusted to factory specs (axles, suspension, steering head and swing arm). The correct fork oil, both weight and volume. It rode like it was on rails, light and nimble as you mentioned. Never had any issue with a wobble and rode it past the ton regularly. Just a great bike. The only mods I did were dual plugs, Dyna III, ‘S’ bars and bar end mirrors.

I wouldn’t change a thing on your bike. Just dial it in and enjoy it.

View attachment 84984

That is one beautiful motorcycle! I'm also thinking about double plugging (as I did on my /6) but I've heard that you don't get that much of a benefit on a 750.... what's your take on this one? The heads are in pristine condition and currently off the bike for modern valves/guides/seats so this is the time.

 

[20774]

I'm also thinking about double plugging (as I did on my /6) but I've heard that you don't get that much of a benefit on a 750.... what's your take on this one? The heads are in pristine condition and currently off the bike for modern valves/guides/seats so this is the time.

I don't believe that the size of the engine determines the benefits from dual plugging. Dual plugging allows the combustion mix to burn more efficiently/completely and use a lower grade of fuel. Snowbum discusses the potential benefits near the top of this page:

https://bmwmotorcycletech.info/dualplugging.htm

He does say that the benefits are greater in the 1000cc models, but doesn't say that the benefits are limited to them.

 

[stevenrankin]

Test riding

I like the post about the test riders confirming over loading and improper loading were the cause of handling problems. Scratch the surface of a lot of handling problems with bikes and I would bet it is the main cause.

As for dual plugging, I had a 77 R75/7, yes I know a newer bike but pretty much same specs. The bike ran great on the highest octane gas I could get and NEVER pinged while the points and timing were proper. The ONLY time it pinged and gave me problems was when the points started wearing and timing changed. Sadly, this was more frequently than I would have liked and at the time there was not much to be done. I traded it in for a R80RT. I have never had a pinging problem with the R80RT even with 9.5 to 1 compression I installed many years and miles ago.

My 78 R100RS had its points replaced by a Boyer system so the timing only changes when I change it or the timing chain goes, which hasn't happened yet. This bike despite European spec engine never pings even on an occasional emergency gallon of regular gas.

I don't know, the dual plug debate and articles went on for a long bit with BMW detuning in the 80's resulting in an end of the problem. Personally, I would ride the bike as it is, see how it runs, make sure the points and timing are set, better yet take advantage of one of the excellent available systems to get rid of the points all together and if need be down the road dual plug. Dual plugging is NOT a performance thing but a solution to a problem. If you don't have the problem you don't need the solution.

I know how my bikes run and ran, I know a lot of guys still riding old bikes that never dual plugged. Honestly, I never read Snowbum's write up about it nor Oaks'. Call me stubborn or other names, I will bet, you can get by with out spending the money to dual plug. If not, well, I am always willing to eat crow. LOL jerk that I am. Good luck and enjoy the bike. St.