Removing selector drum shaft SF1

P

Peter Berry

New member
Location
St Thomas Ontario Canada
I’m trying to loosen the large nut (22 mm??) that holds in the he selector drum shaft . I’m having to put a lot of pressure on it and am afraid I could snap something and the nut is still not moving . Is it a standard right hand thread how much leverage can I put on it . Is there anything holding it on . Peter
 
Standard RH thread. They are generally VERY tight. If a DPO has put thread-locker on it, good luck. :rolleyes:

You can use the nut to push out the shaft against the gearbox wall a few mm. (triples), but then you will need a puller for the remainder, loosening the nut bit by bit.

piet
 
Before I had the original puller, I started off by pushing the nut against the gearbox wall, then return the nut and place a thin open ended spanner and push against that one, followed by a ticker spanner etc. Takes a bit more time, but works well too.

Marnix
 
Last edited:
MarnixSFC said:
Before I had the original puller, I started off by pushing the nut against the gearbox wall, then return the nut and place a thin open ended spanner and push against that one, followed by a ticker spanner etc. Takes a bit more time, but works well too.

Marnix
Click to expand...
I think I did the same, but then the last time was probably my SFC in 93.
:)
Paul
 
I presume we're talking about part number 9 in the attached diagram. I don't think I've ever had that shaft apart before. I've had the gear shafts out to replace bearings but never had to remove a gear selector drum. Interesting to learn that it's super tight. I'll keep that in mind if I ever have to remove one.


shifter mech.JPG
 
Yes, from recent dismantling of a set of 750 cases that had been left out in the weather I can confirm that removal of nut part number 9 to release the shaft part number 24 to free the selector plate item 1 is a long and painful process even with heat and easing oil, be patient it will come!
 
Shim, part n° 14 is vital to a sweetly functioning gearbox. The drum has to be precisely shimmed.
Those big old cogs are pretty finely spaced and shimming that drum is vital to the gearbox set up.

I learnt the hard way.
Freshly purchased SFC bottom case off 3 times in as many days because when hot, in neutral, the box was noisy due to insufficient clearance between cogs. Shims between cogs made of aluminium didn't help either.
Finally got it sorted and the rear sprocket carrier bearing collapsed after 400 km, in the Belgian Ardennes. It did that again in Como in 2017 and then again in Breganze 48 hours later until a missing spacer was diagnosed. Gearbox was fine though.

Paul
 
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