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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Atabeach on December 21, 2022, 03:18:39 PM
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Ok Bike is laid up for winter....1994 k75 7000 miles. Gears change smoothly with firm "click" of lever...however...I can easily get between gears on this bike up or down. Unless I "FIRMLY" it into a gear it will go between gears. Splines lubed, gear oil changed (several times with synthetic) Also, The gear lever is loose...I may open her up to fix the famous set screw...otherwise she changes gears smoothly. If it aint broke? or is this an easy fix? The bike...runs like new. Seven thousand miles.
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It's better not to dwell on whether a task is difficult; just have tools, patience and perseverance. Which reference did you use to adjust the clutch? If you've gone by BMW's K100/K75 service manual to adjust your clutch and have the correct amount of clutch hand lever free play at the end of it all, a loose shifter lever will eventually leave you stuck in one gear or no gear no matter what you've done. How much free play does the foot shift lever have before it starts preloading a shift. Measure movement at the toe pad until it meets resistance.
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Any free play "slop" in the shifter is too much. Sooner or later you are going to have to go in there. The good news is that it doesn't take a lot of expensive tools and can be done in as little as 8 hours of not very intense activity. Figure on 12 hours if you have never worked on a brick before. Most of the time spent is getting to the transmission and putting the bike back together again. Time in the transmission itself is under two hours.
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My 91 K75S has the same issue, most apt to find a neutral when shifting 2-3. Have zero play in the shift lever so there is no loostening screw. This bike also has 7k miles on it, so I decided the gearbox is tight because the bike is new. My remedy is to draw in the clutch fully, then using the throttle try to try match the engine speed to the gear I am selecting. I found no false neutrals that way, even with a cold motor. 112350
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False neutrals appearing at 35,000 miles on my Brick were eliminated by cleaning and re-lubing the splines on the transmission input shaft and clutch hub at 40,000 miles. Until then, the condition was remedied by what you're doing right now, Imiklosy. The transmission input shaft spline lube on a Brick with only 7000 miles is likely to have dried out and become ineffective by this time so the shaft needs to be cleaned and the lube needs to be replaced. It's also important to verify correct clutch adjustment regularly and shift assertively.
I cleaned and re-lubed the transmission input shaft splines again at 81,000 miles.
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I had a lot of false neutrals when I started riding a brick, I was doing a few things wrong. Taking up the slack before changing helped, but as mentioned, if the revs drop too much, the synchros have to work too hard. My biggest mistake, I was changing gears before the revs got high enough. If your previous bike was a cruiser for example, you might be changing too early. Bricks love high revs, and I thinks you will too if you give it a try and get used to it. After a while you might even forget you had a false neutral issue.
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If indeed the bike only has 7000 miles and there is no loose slop in the shifter the problem may be that you are pulling the clutch in too far when changing gears. I have found with the bricks I have owned that shifting is easier when I just "flick" the clutch lever a half inch or so. No need to match rpm or blip the throttle, just fan the clutch and the transmission almost pulls itself into the next gear. Since they have "constant mesh" transmissions with "dog clutches" and not synchromesh, a little drag on the clutch helps with dog engagement.
I suspect that fully disengaging the clutch lets the input shaft slow down too much to allow the gears on it to easily engage their dogs. By just feathering the clutch, the input shaft can more easily go to the speed necessary to engage the dogs.
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Like TMG but worse: I've sometimes gotten lazy and just changed gears without paying any attention to the clutch at all. Especially upshifting, the bike will easily go 1-2-3-4-5 at 5,000 RPM without clutching at all.
I think this might be bad for the bike however, so I usually avoid doing that.
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Just an afterthought, the drive splines on this bike were lubed this year but not the clutch splines, neutrals persist. If I tackle the clutch splines as Mighty Gryphon suggested, will let ya'll know. A permanent fix would be ideal.