Reliability of the BMW motorcycle R60/2 vs. the R69, R69S
This page is about the BMW motorcycle models R60, R69, R60/2, R69S, R60/US, R69US.
Mark asked via email on the slash 2 Yahoo group list.
I’m surprised to hear that the S, with its higher compression, would be more reliable. What was different about the R69S vs. the early long rod R60? I’m familiar with the rear bearing change, the compression increase, and the larger carbs. Was the cam different?
Or could it be more a case of the increased hp allowing these engines to run at (aircraft terms here) 75% power more of their life than at 100%?
Mark, To answer that question takes some time and delving into other areas besides mechanics. Short version. The Interstate system was funded by Eisenhower in 56 (I think), and it was some time till we had lots of high-speed roads. I think that the early /2 models didn’t see the abuse that we expect today as normal. The few BMWs in the USA were mostly in cities, where they may have seen lower speeds too. I wasn’t riding BMW until 62, so I am way out on a limb here. Since I was young and poor, I rode the early /2 bikes, but I wasn’t in the business yet. It was common for one to go 75-100 k miles before the crank needed attention. The R69 got great mileage before it needed top end work. The early engines had a good reputation. It was in 1960, on the R60, when they went to the 4 ring piston that I first saw trouble.
In the 60s, different reliability issues started showing up. It isn’t one simple issue. See my page for detailed info on the evolution of /2 BMW heads and the problems. The R50/2 and R60/2 heads often failed in the first year. The pushrods were prone to bending. The cranks started having problems. The rear mains started spinning on the crank. This issue reached its zenith in 1967 on the R60/2. Everything about the engine was trouble. The pistons were seizing up right and left. Later I found out why, but that’s another story on the piston page on this website. One large problem is that the R60 rear main was a ball bearing. The R68, R69, and R69S use a spherical roller that allows for lots of crank flex.
We finally realized that the 1967, R60/2 was so bad that by 1971 we wouldn’t take one on trade. I parted out several of them. Many didn’t get 25 k on a top or bottom end. I had seen many not even reach the warranty of 6000 miles before the bottom end was out. I used Roy Reynolds, in Salt Lake City, to do my crank work, and even he got discouraged. I tried Flanders, and they didn’t have good quality control. One block was full of sand when I got it back. Reynolds was the best west of the Rockies. I built a special box for a lower end, and it was reusable. It made continuous trips back and forth for a few years. Once, I had 3 new cranks from BMW, and 2 weren’t made correctly and had to be rebuilt before I could use them.
I tried Flanders and they didn’t have good quality control. One block was full of sand when I got it back. Reynolds was the best west of the Rockies. I built a special box for a lower end, and it was reusable. It made continuous trips back and forth for a few years. Once I had 3 new cranks from BMW and 2 weren’t made correctly and had to be rebuilt before use. Plating and welding were tried to build up the rear of the crank to fit the bearing. The welded ones cracked and broke off. The plated ones were better but not as good as original material.
Summary of the comparison of the R60/2 and the R69S BMW Motorcycle
The use requirement went up as time went on. The quality of materials went down during that same time. BMW sales went way down worldwide, as a result, and BMW almost stopped making bikes. Instead, they redesigned the whole thing and did a great job with the /5. It was two years before I could fully appreciate it, but the /5 is a better bike in almost every way than the /2. It isn’t as elegant, smooth, or as soft riding, but the /5 lasts and costs less to maintain.
Both cost about the same to restore. Why in the world would someone spend the same money on an R60/2 that was fraught with reliability problems?
Updated 6 Nov. 2019