Question: 1974 /6 transmission

[blender]

I have a 1974 R90/6 5spd trans with an unknown number of miles. For the past 15+ years that I've had the bike, the transmission has always been a real PITA to get into neutral, even when it's warmed up. I have a few questions about this.

• Is this normal, one of those “Yeah, they all do that” things?
• Is it feasible cost-wise to have the transmission rebuilt/refurbished? Would it make any difference?
• I recall hearing/reading somewhere that a four-speed transmission from the /5 is basically a bolt-on replacement. Would that be a feasible option?
• Any other early /6 transmission-related suggestions? (Other than “buy a later model”. Which ain't gonna happen.)

As always, I appreciate the wisdom and advice.

 

[20774]

I suspect you have adjusted it correctly, but here is Tom Cutter's instructions for doing that...start here first:

http://www.rubberchickenracinggarag...d Clutch Cable Replacement and Adjustment.pdf

In the November ON, Matt discusses some issues with the '74 5spd transmissions. There's a badly designed part for the kicker which is no longer available in the US for replacement, but Matt suggests that a European part might be the answer. While it remains debatable, it's been more or less agreed the the first year 5spd transmission was weak in design.

I have notes that indicate the '74-80 gear boxes are interchangeable and you can put a '74-80 gearbox into a /5 but there are neutral wire issues. So conversely, a /5 can go into a '74 but you'll need to deal with the neutral switch functionality.

With unknown mileage, you might have some wear issues. Matt points out on his article that it was fortunate that the owner's of the transmissions stopped using them to prevent continuing damage. The best plan might be to rebuild your transmission with later parts or buy a replacement transmission but you'll still be facing the unknown with it and it might need overhauling.

 

[stevenrankin]

Unknown

Have you noticed any chips or large amounts of metal on the drain plug? With the unknowns and 15 years of problems, I suggest pulling it out this winter and sending it to someone to overhaul. St.

 

[daz]

You're from Wisconsin. Have you tried a different transmission lubricant? Less expensive possibility .

 

[PAS]

No matter where your from, take time to read some of this info.
https://bmwmotorcycletech.info/transmission.htm

 

[RPGR90s]

I have a 1974 R90/6 5spd trans with an unknown number of miles. For the past 15+ years that I've had the bike, the transmission has always been a real PITA to get into neutral, even when it's warmed up. I have a few questions about this.

• Is this normal, one of those “Yeah, they all do that” things?
• Is it feasible cost-wise to have the transmission rebuilt/refurbished? Would it make any difference?
• I recall hearing/reading somewhere that a four-speed transmission from the /5 is basically a bolt-on replacement. Would that be a feasible option?
• Any other early /6 transmission-related suggestions? (Other than “buy a later model”. Which ain't gonna happen.)

As always, I appreciate the wisdom and advice.

Two biggest issues on the '74 5 speed is the difficulty finding neutral and the lever return spring, which will eventually break. Oh, and another is you want to count the soft kickstart gear.

I had my tranny ('74 R90s) rebuilt after the spring broke on me (leaves you in the last gear you selected), which included a new pawl carrier, that has better designed detent for neutral as well as no more false neutrals between 4th and 5th.

It now has 143k on it with zero issues.

 

[AntonLargiader]

This is totally normal for a ‘74 and installing the shift kit will resolve it. There is a graphic on my website showing why the early 3-4 cam makes it hard to find neutral.

 

[blender]

Sorry for the late response, I gotta pay more attention...

I appreciate all the responses. As to various questions: No, there hasn't been any unwanted (or wanted) metal bits on the oil drain plug. I've heard & read about the early /6 kickstarter and never use it (perhaps I should just remove the bloody thing).

R&R of the transmission might be beyond my skill level, however it appears that might be in my future. I am a member of the ABC and do know several airheads folks in my area. That is a resource I could draw on. And I still need to have a look at those links several of you posted.