The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: cus on 17.09. 2009 01:48
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G'day All,
I have a standard gearbox on my 61 A10 SR, probably wouldn't have done
1,000 miles after full re-build, just finding that when clicking down to mainly
2nd & 3rd it doesn't select that cleanly, gives a bit of a buzz on the gear
leaver then drops in, the same when changing up, its not a major, but
wouldn't mind fixing it, has anyone experienced similar,
regards, Cus
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Sounds more like the clutch than gearbox, I would have a very good look at the clutch first.
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G'day Cus,
I have a similar problem on my '51 plunger. I know the mechanisms are different and if it's not the clutch as Brian suggests, I would first look at the cam plate plunger & spring followed by the quadrant and then the cam plate. It may also be the dogs have rounded off a little. My problem is the claw that engages the cam plate. Sometimes it takes a few (or more) stabs to get 3rd & 4th. The top tooth chips (just put 3rd one in). Now I suspect the cam plate is amiss, but have to remove the motor & split off the g/box just to get to the grub screw that retains the gear shifter fork shaft to get the cam plate out !! Much easier on a S/A.
BSA g/box's are very robust, when racing I only ever used the clutch at the start line. Blew a few motors but never a box.
Cheers
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They say a BSA gearbox needs 5000 miles before its loosened up, but as has been said this sounds like a slightly dragging clutch. presumably you have tried adjusting the clutch?
Have you tried using ATF in the chaincase instead of oil, this usually helps with dragging problems on properly adjusted clutches?
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Thanks for those replies.
I've spent a fair bit of time on the clutch, its
all pretty much new & runs in ATF, push rod was too
short so replaced it, & seems to operate well.
I'll adjust a bit more out of the cable & see what
happens, at the moment there is about 3mm slack
at the lever, I'm always worried about riding
down the pushrod with too little gap.
regards, Cus
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Gents,
A couple of you have mentioned using ATF (automatic transmission fluid ?) in the primary chain case instead of oil, what is the perceived benefit of doing this, does it provide adequate wear protection ?.
What of using EP90 or similar in the primary chaincase ?.
Thanks.
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Not being an oil expert, others will correct me if I'm wrong.
ATF lubes the chain etc very well. It is thinner than the usual grade of oil and doesnt have the slippery additives that oil has. It doesn't "gunge up" the clutch plates like oil will either so clutches tend to run more freely and not bind or drag when using ATF.
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EP gear oils are not necessary or suitable because they are designed for "Extreme Pressure" sliding contacts not encountered in the primary case (roller chain). ATF, OTOH, besides being a lower viscosity than motor oil is designed for use with wet clutches and contains modifiers that increase static friction for clutches but decrease dynamic friction for gears and transfer chains. They also shed better from friction surfaces on the clutch than motor or gear oils. It's like they're MADE for our old bikes.
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Well put Alex & Andy, one more + is it gives less drag, allowing more power to reach the back wheel.
Cus, I hope I was barking up the wrong tree about the box, but I think if it was a clutch prob you would notice it more going from neutral to first rather than second to third.
Cheers
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G'day Muskrat,
Saying that, it can be sometimes a bit stubborn going in to 1st, not all the time,
doesn't crunch, but sometimes have to have 2 goes at it. I'm going to muck
around with the clutch a bit more this weekend, if I don't get any joy from
that, it might be time to open the g/box & see what's going on.
Thanks for all the replies & I'll keep you posted,
regards, Cus
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The higher gears should select and stay put even without the clutch. Popping out usually points to worn dogs. Improper shimming of the shafts can also cause this as well as trouble engaging in the first place.