Replacing A10 High Gear bushes

[sprint]

What is the best way to remove and replace the high gear bushes?  Can they be drifted/pressed out and are the replacements pre-sized or do they have to be reamed after fitting?

[chaterlea25]

Hi
The original bushes were steel backed split bushes which should be the correct size when fitted
Unfortunately these are no longer available
What to do???
Solid phosphor bronze bushes are available, These should be pressed into place after pressing out the old ones
I made a stepped mandrel to remove and fit the bushes
The set I got most recently for a STD box were too long and needed shortening
The 3 oil holes need to be drilled  in the inner bush to match the holes in the high gear

The centre portion of the original bushes were relieved to leave a "pocket" between the two bushes
Was this to hold a drop of oil?? I machined the inner bore to simulate this relief because
I made the mistake of fitting a long solid bush without the centre relief on my own SR
It seemed fine on the bench but siezed after a mile or two

I have seen short bushes with a gap between them to achieve the same thing but I have also found the short bushes have moved in use
Then the solid PB bushes need reaming to size,  with 2 thou clearance
Of course the mainshaft will have an unworn part where the gap between the bushes were
which making a nice fit very difficult
I have polished down the unworn part in the lathe to get a uniform size

From memory doesn't your bike have an RRT2 box ?
These have a needle roller bearing plus a bush in the high gear

HTH
John

[sprint]

Hi John

Thanks for the reply. Yes my RGS has needle bushes, I'm helping a friend do his A10 which has rather a lot of play between the mainshaft and high gear and is dripping oil at lot.

Don't have the luxury of any machine tools, lathes etc so I guess it will have to be the old hacksaw blade down the bushes. Could you advise what the dimensions are of the drift you have made, may be able to find somebody who would be able to machine that?

I guess the only way to ream them will be with an adjustable reamer as there is bound to be some wear on the mainshaft that has to be compensated for? Are the cheap ones found on e-bay good enough for what will be a one off job?

Am I right in believing that with the clutch off that you can remove and re-build all the gearbox internals in situ without having to remove the gear selector  shaft? Don't want to remove the box from the frame but getting the selector shaft grub screw out may be very difficult if not impossible?

[KiwiGF]

Depending on how much needs to be taken off the bush i.d. after fitting you might get away with u sing a cheap honing tool made for doing brake cylinders.....I used one when doing the gearbox sleeve gear bushes...it worked well.

[chaterlea25]

Hi
You will need to remove the selectors/ shaft to get the gears out of the box
Its not a lot of extra work to remove the top gearbox plates when the primary case is off if you cannot get out the grub screw holding the selector shaft
The stepped bush remover measures approx 5 1/2 in. long, 0.800 dia and 0.900 dia with the step centre ways
Cheap adjustable reamers rarely cut parallel 
The bushes should be reamed to 0.8125in. (13/16ths) the new solid pb bushes I fitted measure 0.806/7
so need 5-6 thou removing
Thats enough to make a pigs ear of the job without the proper tools !!!!!

If the bushes are well worn I'll bet theres wear on the mainshaft too!! Its possible to grind the shaft a little undersize and make bushes to suit

So (If I was You) I would either find a local engineering guy who would have the necessary tools and experience to do the job
or
send the parts to a known BSA specialist to be sorted

I have fitted several of the sealed gearbox nuts from SRM which cure a well known leaky point on the A&B BSA's

HTH
John



 

[sprint]

Thanks for the replies.

We do intend to fit a SRM nut with the oil seal, but feel that the amount of play really needs sorting. SRM are supplying the parts and apparently they now supply a long single bush?

Can the mainshaft be removed with the selector forks still on the shaft/? Hopefully it can as we don't want to have to remove the complete box.

Once the parts are out it can be decided the best way to remove the the old bushes?

[duTch]

 The mainshaft comes out with the inner cover which has to come off regardless, but to get the sleeve gear out, you need to  pull the selector shaft and all the guts- no shortcut.
 It really is not difficult, takes FA time and is good to do- call it practice if you like, learning curve is probably more appropriate.
   Reassembly is easy too, but you need to think about it. Is wroth doing a couple of times for the hell of it- takes about ten minutes if you stop for a coldy or two.
 The serious reassembly takes a small bit longer, just Remember how it came apart

[sprint]

Managed to get the selector fork shaft grub screw out in situ with some heat as it was well and truly tight, possible loctited in?

Now have to decide how to do the rest? Looking down the bore of the high gear it looks like there is a machined step which the bushes press up to, is that correct as if so it will not be possible to drift either bush out?

[chaterlea25]

Hi Sprint,

Looking down the bore of the high gear it looks like there is a machined step which the bushes press up to, is that correct as if so it will not be possible to drift either bush out?

Thats the reliefs machines into the old bushes, usually the bronze is machined away to show the steel backing metal
There is no step in the gear bore
My experience's lead me to believe that the relieved portion in the middle is needed
The SRM one piece bush is a lot thicker than the originals as it needs to be stronger to withstand the pressure of being pressed all the way from one end
It was the SRM bush that siezed on my bike ( I had not machined the relief in it )

To size the SRM bush I had to machine up an alloy piece with a slot cut in it and a clamping screw to hold the high gear in the lathe
it was bored in the lathe to accept the gear bearing surface, then the bush bored to size
This was to make sure gear and bush bore were perfectly concentric
It was a pain in the idiot to do all this 

For the box I did most recently I got the parts from Autocycle Engineeering , ie bushes need 0.006 removing
and the centre relieved

Have a read of this post on issues  fitting the sprocket seal
http://www.a7a10.net/forum/index.php?topic=8786.msg62713#msg62713

If you cannot find someone to do the bush fitting and sizing locally , You could always post me the parts and I can do it

HTH
John

[KiwiGF]

we are talking sleeve gear? if so here is a pic of the $20 (10gbp) brake cylinder honing tool I used to ensure I had about 002 clearance on new sleeve gear bushes. It worked really well and only took a few minutes, it was easy to take off  little at a time, working the way along the bore a bit at a time ........as reported above I also had the sleeve gear seize after fitting new bushes  and concluded I either was supplied bushes in the wrong material eg brass, or because I fitted them without reaming them (my Draganfly supplied bushes were near exact to size) they had insuffient clearance.

[KiwiGF]

and heres a link on sleeve gear replacement including some pics of tools to assist in removing them http://www.a7a10.net/forum/index.php?topic=5202.0..

[chaterlea25]

Hi Kiwi,
The reasons I do not use a hone like the one in your pic are,
The hone stones can embed abrasive particles into the bush metal
The spring loaded hone will follow any undulations in the bush and does not correct any distortion
The long stepped mandrel I described earlier can be used to keep the bushes straight while pressing the new ones in as well as being used to removing the old
Works for me!!

Cheers
John