The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: RDfella on 12.09. 2017 19:20
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Hello folks,
Here's another issue with the pile of junk I'm converting into an A10. OK, well I'm a bit miffed with this bike. Been nothing but grief at every turn - what wasn't worn out had been bodged. Or both.
Gearbox. Fully restored - ground shafts, new bushes to suit, new 3rd gear, kickstart parts etc etc. Selects fine with the outer cover off. With cover on, it's a lottery as to what one gets - usually a neutral and 2 gears. There are no worn parts left in this box. Selector claws are fine with new springs etc etc.
I'm now wondering if the indexing is out. I attach 3 pics - one a modified plunger for easier shifting (which I've now replaced with the original in case that was the problem) and two indexing ones. One is taken from this site, and mine. Mine is the slightly misaligned dots. BUT, when I rebuilt it, if I moved it around one tooth it was equally misaligned the other side. Reckon that's the problem before I strip it further?
Thanks.
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I see only one pic loaded - here's mine and the one copied from this site (I added the yellow arrows for my own clafification)
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not at all unknown for the dots to be misaligned to get the box to work.
On one of my bikes I had to use two gaskets on the outer cover, it worked and is still working fine that way
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I'd think that 'modified' roller plunger would work better than the original *dunno2*..
I'm assuming you're spinning the drive sprocket/mainshaft as you try and select gears ??
If you do need to strip it again, check the selecting as you progressively undo the fastenings and it may indicate.....?something?
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Hi,
You need to turn the input and output shafts separately to find all the gears
Th marks look correct
Operate the quadrant arm with a screwdriver, you can slacken off the detent to make this easier
with the outer cover off, can you find the 4 gears then?
With one tooth out the arm will usually hit top or bottom of the case preventing finding first or fourth gear
With the inspection cover off check that each selector is holding two gears in its groove
John
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Also check the position of the gears themselves.
Some times you need to shim the layshaft to get the gears to mesh properly.
Double check and tripple check your selector forks there are a few variations.
No reason to believe what is in the box when you pulled it apart was the same as what was in it when it left BSA
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Bsa54A10 - agree with what you say. This bike has clearly been worn out and rebuilt / bodged several times. Can take nothing for granted, but the box seems to have avoided their attentions, given the amount of wear in it. Layshaft wear was worst I've seen on this type of box so I reground it (after straightening it - it was bent as well) and made an U/S bush to suit. All seems OK now.
chaterlea - with outer cover off, selection of gears is fine with a screwdriver - 1, N, 2, 3 & 4. Seems the claws are not picking the quadrant properly, but there's very little wear on these components and the lever has new centralising springs.
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why not try 2 gaskets as suggested by Bill on the outer cover ,worth a punt .
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Thanks for the input, folks. As I wondererd at the outset, it was quadrant indexing. When I re-assembled the box the dots didn't line up exactly, so I chose one option. This afternoon I pulled the inner cover just enough to free the quadrant and tried it in the alternative (almost lined up) position. Now works as it should. This bike has been a long haul, what with cracked frame, non-matching crankcase halves and a long list of other disasters (including the now-resolved lack of oil flow) so guess I'm starting to get tired of it. Almost there, though. Just the front brake to sort (converting to TLS) and the refinished tank to refit and I'm (hopefully) there.
Thanks again folks for all the helpful suggestions.