K75 Gearbox Drip at Boot - Gearbox out or not? 49k miles

[bluebossa]

Howdy again,

Just purchased a new to me K75C with 49k miles, good original condition Bike that works great...
Couple of pics attached... Original faded Paint, everything intact from 1986.

Drove it home from London to Derby circa 150 miles, not an issue, though its been off the road according to MOT History from 2010 to 2026 - 16 years.
Amazing testament to the way these Bikes keep going. I love em.

Anyhow, noticed a small pool of Gearbox Oil underneath the back end... Clear Gearbox Oil
Just took a couple of shots and been researching seals...

Looks like it was inside the Rubber Boot, which has perished and needs replacing... Do I need to replace the Clutch Pushrod Oil Seal alone, will that fix it?.
Can I get away without taking the Gearbox off?

Thanks in advance...

[Laitch]

It's unlikely the clutch rod seal is leaking. Replacing it in a K75 would require removing the transmission to extract the clutch rod for access to the seal.

The common reason for the boot rip is allowing the swing arm to drop its full length of travel when removing the rear drive. Doing that allows the boot to be hyper-extended then rip in its weakest area. That is what might have happened in your case.

The common reason for transmission oil to leak from a boot that isn't ripped is given below.

[bluebossa]

Thanks Laitch, I've ordered a new Boot seal as it fell to bits, per pictures...

Don't believe Gearbox or Drive have ever been off... planning to replace Boot and re-adjust Clutch play, according to that bulletin then, that would solve it... no seals involved?

[Laitch]

As long as the gear case isn't overfilled with fluid and the clutch is adjusted strictly by the book, that's the least complicated method to determine if more work is necessary.

[bluebossa]

As long as the gear case isn't overfilled with fluid and the clutch is adjusted strictly by the book, that's the least complicated method to determine if more work is necessary.

Thanks Laitch, Clutch cable is a bit scratchy so going to treat it to a new cable from Venhill, then adjust as per guidance, remember that process from previous K75.
I'll then fit the new Boot and see how I go on and if it stops... will report back when complete, parts enroute.

40 years seems a decent period to have a new Clutch Cable... Thanks for the Maintenance Pics...

[Laitch]

Greasing the barrels at the end of the cables helps smooth the action and inhibit cable breakage. Greasing the pivot pin of the clutch release arm also helps the hand lever action. The clutch release arm area can be a gritty environment.

[bluebossa]

Thanks Laitch, Bike was laid up for 16 years so a bit of TLC in order... hopefully, Boot and Cable will tell me whether any seals need doing...

In your experience how long do the Gearbox seals last?

[Laitch]

≈100,000 miles in my Brick so far. Although I have read a couple of threads about transmission cover seals needing replacement, I've only read one concerning replacement of the pushrod seal. Regardless, they're all doable when necessary.

[bluebossa]

New Rubber Boot came this morning from MotorWorks - £21 inc VAT

So a happy hour or so later I'd taken the Exhaust off, cleaned the whole area up, dismantled the disintegrated old boot - picture attached.
Fitted the new boot and done a complete reset of the Clutch Cable clearances as per spec - thanks for the nudge Laitch in the right direction.

I took it for a 10 mile blast in the Derbyshire Peak District, UK where I live and so far its as dry as a Bone.
I've put a tray under and will check it in the morning, but I think that was it... fingers crossed...

I may have some Gearbox seals to return now, as I was getting ready for the worst.
This has saved me taking the Gearbox off so THANK YOU again for the correct guidance... here's to K75s.. onwards

[Scott_]

If it were me, I'd keep the seals as long as you already have them. You most likely will need them at some point.
Murphy would say that if you send the seals back, then when you do need them, you won't be able to find them....

Just food for thought.....

[Ingo]

Actually: according to Muphy once you return the seals your current ones WILL fail...