Shift spring breakage

RonH

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#23
Looks like the same basic spring setup used since 1970s if not before. No need to worry, just ride.
 

blitz11

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#25
Had that spring fail TWICE on my BMW 1971 R60/5. Once on a ride with my wife in 1992 (i had had the bike for 15 years at that time, but hadn't ridden it much with college/grad school / work) and once in 2014 on my way to visit a customer. That was the final nail in the coffin for my bmws. The second failure allowed the shift drum to wander, and tied up 2 gears (1'st and 2'nd). Broke a tooth on one gear (found it on the magnet in the Trans oil drain), and that was it. I had a spare transmission (known weak point) that i had gone through the previous winter (new bearings, reshimmed, new spring), swapped it in, sold both BMWs (ended up in a bidding war in my favor), and bought my super 10. Haven't looked back. I liked the bikes, but trying to make a reliable bike out of a 40 year-old motorcycle is tough. Easy to fix, but it was always breaking. IF i rode it on a trip of more than 1000 miles, it always needed something.

The second spring that broke was only 3K miles old. put in about 2 years earlier when i replaced the bearings in the original transmission when i did a full rebuild of that bike.

Metal fatigue is really dependent on the quality of the material in this application - statistically, some ARE going to fail. Hopefully, the fatigue is manifest in obvious poor shifting (as mentioned above) and can be caught before things good badly.
 

Checkswrecks

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#26
blitz11 said:
Metal fatigue is really dependent on the quality of the material in this application - statistically, some ARE going to fail. Hopefully, the fatigue is manifest in obvious poor shifting (as mentioned above) and can be caught before things good badly.

While true, fatigue is also dependent on the load and a couple of other things. My guess is that the BMWs have theirs under higher load.
 

OldRider

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#27
blitz11 said:
Had that spring fail TWICE on my BMW 1971 R60/5. Once on a ride with my wife in 1992 (i had had the bike for 15 years at that time, but hadn't ridden it much with college/grad school / work) and once in 2014 on my way to visit a customer. That was the final nail in the coffin for my bmws. The second failure allowed the shift drum to wander, and tied up 2 gears (1'st and 2'nd). Broke a tooth on one gear (found it on the magnet in the Trans oil drain), and that was it. I had a spare transmission (known weak point) that i had gone through the previous winter (new bearings, reshimmed, new spring), swapped it in, sold both BMWs (ended up in a bidding war in my favor), and bought my super 10. Haven't looked back. I liked the bikes, but trying to make a reliable bike out of a 40 year-old motorcycle is tough. Easy to fix, but it was always breaking. IF i rode it on a trip of more than 1000 miles, it always needed something.

The second spring that broke was only 3K miles old. put in about 2 years earlier when i replaced the bearings in the original transmission when i did a full rebuild of that bike.

Metal fatigue is really dependent on the quality of the material in this application - statistically, some ARE going to fail. Hopefully, the fatigue is manifest in obvious poor shifting (as mentioned above) and can be caught before things good badly.
I'm going to say you had the shift drum detent spring break. That is the spring that holds the shift drum and keeps it from turning on it's own.

This spring in question here is the spring that centers the shifter in the middle. When you push the shifter up or down and feel a little resistance, that's this spring doing it's job.
 

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OldRider

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#28
One more thing about this spring. The peg that it straddles in order to center the shifter also acts as the stop for the shifter. When you push up or down on the shifter it will hit this peg to limit it's movement. This spring just breaks on it's own, not rider error. You can push up and down on the shifter as fast and hard as you want to without hurting the spring.
 

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scott123007

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#29
OldRider said:
One more thing about this spring. The peg that it straddles in order to center the shifter also acts as the stop for the shifter. When you push up or down on the shifter it will hit this peg to limit it's movement. This spring just breaks on it's own, not rider error. You can push up and down on the shifter as fast and hard as you want to without hurting the spring.
Exactly!




And one more "one more thing". In its "resting" state, this spring is under virtually no load. It slips over a little tab on the shifter shaft barely spreading at all, and only becomes tensioned when either upshifting or downshifting. They do fail on occasion, but it is one of the rarer events of engine/transmission malfunctions.
 

blitz11

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#33
OldRider said:
I'm going to say you had the shift drum detent spring break. That is the spring that holds the shift drum and keeps it from turning on it's own.

This spring in question here is the spring that centers the shifter in the middle. When you push the shifter up or down and feel a little resistance, that's this spring doing it's job.
Good point. The FIRST spring which broke was the shift lever return spring. The second which failed, as you accurately pointed out, was the shift drum detent spring. I guess my memory is good, but just short.
 

Ramseybella

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#34
WJBertrand said:
Looks like the clutch basket needs to be pulled to replace the spring?
And apparently the shift shaft along with it to pull the spring and install it as it's behind the clutch side of the shaft.
While you have it apart i wold replace parts 10 through 14 and maybe #1 hanger spring..
Just me $40.00 $45.00 in extra parts for reassurance.
 

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OldRider

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#35
Ramseybella said:
And apparently the shift shaft along with it to pull the spring and install it as it's behind the clutch side of the shaft.
While you have it apart i wold replace parts 10 through 14 and maybe #1 hanger spring..
Just me $40.00 $45.00 in extra parts for reassurance.
I would take a look at those #11 bearings and if they are clean and oily, I would leave them alone. They are probably going to be a bear to get out and you risk damaging the new ones putting them in. As long as those bearings don't get water in them, they will probably outlast the motorcycle. JMO.
 
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