A10 gear box problems

[rgsjohn]

BSA A10 gear box. Got a problem that I can’t seem to get to the bottom of. Initially when I first go for a ride and everything is cold, the gear change is noiseless and smooth. Selecting neutral from either 1st or 2nd gear while stationary is easy and reliable. After everything has warmed up selecting neutral becomes very difficult, and the best way I can describe it is that gear shift  almost feels as if it is seized solid and will not select neutral at all. This happens after about 15 miles or so. I have replaced the selector forks, and “claw” in the gearbox, and spent a long time setting up the clutch with a dial gauge and according to the guage the pressure plate is lifting absolutely square (four spring clutch with SRM ally pressure plate and radial bearing fitted to the clutch push rod). I have replaced the clutch springs, cups, and spring adjusters too although these symptoms were there before which is why I replaced these items. Gearbox oil is 50 weight  and primary chain case has ATF in it. While riding along the gears change just fine, and it is not until I stop and try to select neutral that I notice any problem. I am lost as to what to investigate next. Anyone got any ideas or suggestions as to what might be the cause of this problem?

[john.k]

If you have replaced the six spring clutch,then you are on the right track......check the plain plates are flat,not buckled........its also possible the friction material expands with heat...........The only sure cure is the old A10 trick of selecting neutral while still on the move.

[33d6]

Excessive mainshaft end float allows the whole body of the clutch to move outwards when pulling in the clutch lever. This means the plates don't quite clear and everything drags a little. Neutral is then difficult to find.There may be just a  touch too much end play when everything warms up and expands after a run.

Cheersd,

[Rex]

If you have replaced the six spring clutch,then you are on the right track......check the plain plates are flat,not buckled........its also possible the friction material expands with heat...........The only sure cure is the old A10 trick of selecting neutral while still on the move.

On the A7/10 forum the consensus is the BSA 6-spring clutch was the best design, although in this case my suggestion would be clutch problems rather than anything wrong with the gearbox.

[john.k]

The design may have been OK,it was the crap quality of the pressed tin parts that was the problem......I replaced mine with the whole assy from an army beeza.....the tin cover is a must,or it will slip,Worked like a charm.....no more chipped and busted gears,no more bronze bushes jammed with steel chips scoring shafts away.The army bikes had all machined and hardened steel parts,the army wouldnt have put up with rubbish like the swingarm A10......the plunger A10s had a decent clutch of very similar type,all machined steel,which worked well.

[rgsjohn]

Thank you all for your comments. Excessive main shaft float movement sounds plausible is that an easy job to do? How exactly would I measure the end float? I am not really mechanically minded, but I'm quite happy to have a go. Definitely need to resolve this one way or another because I am not riding the bike. There is absolutely no pleasure to be had riding it as it is. The handle bar levers are Doherty ball ended levers, the clutch is reasonably light in operation can be operated with one finger at a push and very easily with two fingers. As for the old A10 trick of selecting neutral while still rolling until everything has warmed up, their is no need to do that I can feel it going into neutral when stationary it is that good. On the other hand once it has warmed up selecting neutral even when still rolling is hit or miss (miss mostly). And if it does go into neutral it can be a bugger to get it into gear. After a few attempts it will go in with a crunch. Easier to "ride the clutch."  Not good I know but at least I am not in any danger of stalling the engine. Like I said, no fun to ride like that. If something in the clutch is expanding once warmed up it must be by quite a large amount because before I replaced the primary cover when the clutch lever was pulled in I could here the plates rattling about. I suppose it might be worth backing the springs off to see if it makes any difference. Deffo something strange going  though.

[chaterlea25]

HI All

On the A7/10 forum the consensus is the BSA 6-spring clutch was the best design

I believe they are referring to the plunger model clutch, not the S/A one

Magnetoman has posted a long and detailed rebuild of a six spring on Britbike.com
However there is no mention of town driving with it 

There should be no end float on the BSA gearbox
If the kickstart ratchet nut is loose or the small bearing inside the ratchet is worn endfloat will be apparent
RTM

You do not say what brand friction plates are in the clutch?
Basically anything other than Surflex brand are crap (unless you opt for the 7 plate conversion)
A remote possibility is that a clutch plate is warping when it gets hot (Yes it has happened on one of my bikes)
Crappy imported inner and outer baskets will cause more problems sooner than later
Lastly,
ATF ? is for automatic transmissions not clutches, it absorbs air bubbles
I use oil intended for modern bikes with wet clutches 10/40 grade (NOT car oil)

John

[Rex]

HI All

On the A7/10 forum the consensus is the BSA 6-spring clutch was the best design

I believe they are referring to the plunger model clutch, not the S/A one

Yep, quite correct, they are.

[john.k]

You can check mainshaft endfloat roughly by pulling and pushing on the whole clutch assy....if you think its moving,then take out the pressure plate and plates ,and check endfloat on the clutch centre........which is rigidly attached to the mainshaft.....or should be.......Incidentally,the clutch pushrod adjuster often takes up shaft endfloat on bike boxes,shouldnt,but does............................I am still suspicious that your friction plates are expanding with the heat..................IMHO,autotrans fluid should be very suitable for a wet clutch,but its a very penetrating mix,and may be incompatible with your clutch lining material.........I do know ATF causes some synthetic materials to swell .