I set my end float on all three shafts, at near zero end float without a gasket. The original gaskets are 7 thou. So once the gasket is installed I'm happy with 7-10 thou end float. Ron

email (option): ronpier@talk21.com

Hi Micah,

Yes if all is shimmed correctly the shifting forks will only see a side load when changing gears. Once you are in gear the shifting forks should be doing nothing and should be free to move side to side a little bit. If they can't move a little bit they are rubbing on the the gear dog clutch and will wear out as they are not allowing the gear dogs to fully engage.

What Ron recommends is correct for shimming but you still need to look inside the gearbox to see what is happening.

I will say it again, THERE IS A REASON BSA PUT AN INSPECTION COVER ON THE GEARBOX! SO YOU CAN SEE WHAT IS HAPPENING INSIDE. IF JUST HAVING IT SHIMMED CORRECTLY WAS ALL THAT WAS NEEDED, BSA WOULD NO HAVE SPENT THE MONEY TO PUT THE INSPECTION COVER ON THE GEARBOX!

Here in the USA the M20 is not as common as in Europe, and especially the UK. But we have lots of rigid and plunger B series with this gearbox. Almost all I have seen are a disaster due to incorrectly assembly. Absolutely no one here ever looks in the inspection cover to see if they put it together correctly and wonder why the gearbox does not work.

I removed the oil tank today and checked it, there’s no problem as far as I can tell. End float is .010” on layshaft and selector shaft. I’m feeling pretty confident with it, but I’ll keep an eye on the oil anyway. I’ve ordered some magnets for the sup plugs to make it easier to check.

email (option): Micah.leinonen@gmail.com

This is a gearbox life extender.

https://pesltd.uk/?product=28-0043

Mark

email (option): pes.sales@btconnect.com

I’ve already glued a magnet into my plug but thanks anyway

email (option): Micah.leinonen@gmail.com

I may have found the problem. My gearbox mounting plates have a nasty bow in them. And although my spacers are in the correct orientation, it appears as if 2 of them have been ground down. I’m going to try and straighten them and order the correct size spacers and hopefully this will fix the problem.

email (option): Micah.leinonen@gmail.com

If you decide your mounting plates are too much trouble Micah, these work well.

https://pesltd.uk/?product=66-4157

Mark

email (option): pes.sales@btconnect.com

measure the width of the mounting lugs on your gearbox
good chance some one has fitted the early narrow box where a latter wide box should be fitted.
read the article in the technical section.

The mounting lugs are exactly 2.5” which I think is right. The frame section that attaches to the plates is slightly less at 2.475”. Should I shim it or was that intentional?

email (option): Micah.leinonen@gmail.com

I’m pleased to confirm that straight gearbox plates and correct spacers fixed my primary sprocket alignment problem.

email (option): Micah.leinonen@gmail.com

In the parts list for the RAF outfits, a 17T sprocket was used. But they did tend to under gear stuff back then. I think I'd try the 18T. Ron

email (option): ronpier@talk21.com