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Discussion Starter · #1 ·
OK... when I acquired the bike (1970 A50) last year I replaced the gear box oil to find that it poured out white after sitting for 25 years. Water... no doubt. I have since replaced 80/90 hypoid oil twice in the course of 100 miles to clean out the old stuff.

The down shift to 1st isn't that bad. Typical I suspect. The clunking is really bad in the up-shift to 2nd, a lesser clunk to 3rd, and a smooth seamless shift to 4th.

Here's what I've done... Firstly, the clutch pressure plate does run square. The springs are in sound condition with no undo tension. No slipping is present in the clutch mechanism. Even though the workshop manual says to turn out the adjuster one full turn on the push rod I have tried a 1/4, and 1/2 turns with the same results. The only difference is in lever pull (when the clutch engages/disengages). I have found that one full turn produces clicking at the ball ramp, which is eliminated at the lever by lessening the adjustment, producing a sloppy lever feel. Presently, the lever has a light pull and engages near the end of its leverage.

It's riding season, and I don't want to tear into the GB if I don't have to? Any ideas to eliminate this painful malady?
 

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Is your clutch rod mushroomed on the end? Are you missing the ball bearing typically found at one end of the clutch rod?
 

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Discussion Starter · #3 ·
Is your clutch rod mushroomed on the end? Are you missing the ball bearing typically found at one end of the clutch rod?
Clutch push rod is OK. It did occur to me that the ball bearing may have been misplaced. I never saw it on the garage floor. :D I will check for the this. Thanks for the reminder.
 

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Your transmission gear bushings may have gone a little tight due to the water in the oil...You could try using synthetic oil in the gearbox, I find they seem to shift a lot smoother with it.
 

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Castrol is what I generally go for, but since you're in "T-O" you could use the Motomaster 75/W90 stuff from Crappy Tire. I've used 'em both with similar results.
If that doesn't work, and I know you don't want to hear this, but you may have to dismantle the gear clusters and clean up the shafts and bushings...it might be the best bet anyway as the needle and ball bearings may have received some corrosion damage.
 

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You might also try one of the molybdenum gear oils.
 

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I have since replaced 80/90 hypoid oil twice in the course of 100 miles to clean out the old stuff.
First take that out of there and put a proper GL-4 spec EP90 gear oil in there before you make things worse. Hypoid gear oil (GL-5) is meant for hypoid type gears and does not really work properly with your straight type gears in your transmission. It also does not contain the proper compounds to protect yellow metals and you have a bunch of bronze bushings in your gearbox.
 

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Pull the clutch plates and check for buckled ones and for notched drum,either could lead to a bit of drag causing gears to clunk on the shift,but with milky oil a quick strip of box maybe not a bad idea
 
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