The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Steve on September 13, 2025, 05:31:22 PM
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At 148k miles my 1979 R65 started developing roll-on / roll-off bucking. At 174k miles I ran a thread here to discover its cause and found that it was lash in the drive train, especially in the final drive due to wearing teeth. I replaced the final drive with one with very few miles on it. The lash went away but 5k miles later the lash is back. Is it because the teeth in the final drive and in the wheel are a matching set and both should be updated at the same time (get a new wheel or repair the splines on it)? Or has some other component started to wear, like the drive shaft spring and coupler? This question should apply to all air-heads of any year. What do people with high-mileage bikes do about lash?
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I would have thought the majority of drive train lash occurs due to wear in the rear wheel splines rather than wear in the mesh of the final drive teeth. There's also the spring loaded cam in the the rear drive shaft which may need to be checked.
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How would one address wear in the rear wheel splines? How many miles on your R45?
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You can visually inspect the rear wheel splines. Here's an example of a badly worn one where more than half the spline thickness has gone.
You can do a simple measurement of the total lash in the drive train. On the stand, put it in first gear them lightly rotate the rear wheel by hand measuring the lash at the outer edge of the rear tyre. I get 22mm but it's only done 30,000 miles. Note this measurement will vary a little depending on the final drive ratio and vary a lot depending on which gear you put it in.
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I've seen those teeth before!
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Barry, sorry to be a dunce, but is that a picture of a rear wheel? Is part of the rear wheel removed to make it look like that? It's been a while since I had my rear wheel off but I don't recall it looking like that.
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Steve, the male part belong to the drive. The wheel hold a female part which is more difficult to check because the wear is concealed inside the cup.
If your final drive looks like the one Bob shows, time to get action....