Boxerworks.com

Hi ,
Well i have just opened up my gearbox its 1978 R80/7 , the intention was to replace the input shaft as the splined section for clutch plate is shot . But when i took the cover off i noticed some additional parts to the shift cassette , a couple of counter weights had been welded onto the selector pawl the only rational i could think of was it was an attempt to build in a fail safe if the famous spring breaks and the selector pawl drops leaving you stuck in whatever gear your in at the time .
This over centre counter weight would hold the shift pawl up but its putting extra strain on the already notorius spring.
anyone got any other thoughts or come across this modification before ?
Also it would account for the very stiff gear change i found on the bike when i bought it last year. cheers

That #$%^&*@! pawl spring is the Achilles’ heel of these transmissions.

After the first few unscheduled breaks at approximately 160,000 km intervals, luckily stuck in 2nd or 3rd gear so I could ride it home, I started begrudgingly replacing the little bastard at 100,000 km intervals as part of my self-inflicted scheduled maintenance plan.

I’m not sold the counterweight idea unless it can be demonstrated that the transmission will shift (as) perfectly with the spring permanently deleted… otherwise , you’ll still have to take it apart if when the spring breaks. The bob-weight mod might permit shifting when your spring does break, but I think it will hinder the shifting experience the rest of the time..

in a perfect world, some genius with a PHD in metallurgy would re-invent what was probably acceptable spring steel technology and material 50 years ago with something indestructible that NASA would use on the space shuttle today. I would gladly pay an exorbitant price ($100!?) for an exact unobtanium replacement for this $2 chineseium BMW crap spring.

To keep things in perspective, I just replaced a broken spring that has a similar function in a friend's 998 Ducati a while ago.
It had only 30,000 kms on it.

To be fair, 160,000 k is probably considerably beyond the design life of any vehicle made in the '80s or '90s. Doesn't make it any less annoying of course. With the estimated average life of a gearbox without rebuild being somewhere between 100,000k and 120,000k it certainly make it something that should be replaced with every strip down.

Rob

Thanks for input , yes will be visiting Moto Bins for a new selector pawl, they are around £36 or
Might try Motoworks for a used cassette of the 1982 version with the bigger spikes on the cam that is supposed to eliminate the false neutrals of the earlier shift cams.
decisions decisions!!