Gearbox = coffee grinder

[Greybeard]

Sounds like a pretty good deal.

I hope so. I may have been able to do this work myself but I thought what the heck lets get an expert to sort it so I know I don't have to take the darned thing off the bike again in the near future!

[duTch]

 I can't help thinking Organ Grinder when I see this topic   
 

...I may have been able to do this work myself but I thought what the heck...

 Well yeah but it just might've needed the shady cleaned up or bush reamed just enough for it to go to crap DAMHIK 

[Greybeard]

Well, now I've seen all the bits Richard Clamp changed in my gearbox I'm even more impressed with the price he charged me. Looks like he changed everything!

[beezermacc]

Told you so!  (Don't you hate it when people say that?!)

[Greybeard]

You will find a link to Richard Clamp, among other services here.
https://sites.google.com/site/cheshirebsa/services
He doesn't have a website. This is his email address: cazo57@hotmail.co.uk

[RichardL]

Really? He replaced all of that? Maybe you should send him a bonus.

Richard L.

[RichardL]

Note to self: check gearbox oil TODAY.

GB,

Get on a plane and fly to Chicago because I am buying you a dinner and beer (but not air fare and lodging, sorry). My gearbox was down by about 3/4 capacity (1/4 capacity left). Really, you didn't need to blow yours out just to save mine, but I appreciate it.

Richard L.

[Greybeard]

Note to self: check gearbox oil TODAY.

GB,

Get on a plane and fly to Chicago because I am buying you a dinner and beer (but not air fare and lodging, sorry). My gearbox was down by about 3/4 capacity (1/4 capacity left). Really, you didn't need to blow yours out just to save mine, but I appreciate it.

Richard L.

OK, see you soon.


I really ran the gearbox dry to encourage everyone to check theirs. I'm selfless like that.

[Greybeard]

Following gearbox overhaul from my semi-unit Plungy:
I have the engine/gearbox assembly in the bike frame. The head is still off. The clutch is still off. I've filled the gearbox with oil up to the level plug hole. I've been playing with the gear changes, first by turning the kick starter and then by turning the mainshaft. I'd like you to tell me I'm paranoid but the gear changes don't feel as positive as I'd like. I'm not sure I've been able to get into fourth. Is it likely that everything will be ok when the engine is under load? 

[beezermacc]

You get a better impression if the back wheel and chain are on. Then you can try the gears when spinning the back wheel. Gearboxes always feel awkward when not attached to anything. I'd be very surprised if it isn't right because Richard will have tried it on the bench.

[Greybeard]

You get a better impression if the back wheel and chain are on. Then you can try the gears when spinning the back wheel. Gearboxes always feel awkward when not attached to anything. I'd be very surprised if it isn't right because Richard will have tried it on the bench.

Thanks Andrew, that's what I wanted to hear. 

[Greybeard]

After completing the reassembly of my gearbox and engine I was gutted to find that gears were not selecting properly. Oh boy I was not happy to think that I'd have to take the engine out again! I spoke to Richard Clamp who'd renovated the box. He said that he had fitted a gasket on the inner case because there wasn't one on the box as I'd taken it to him. I had a feeling that I'd read something on this forum about plunger gearbox gaskets so I searched the forum and from various posts I could identify that I probably had the same symptoms. With Richards agreement I stripped off the gearbox covers and quickly refitted them with no gaskets. Gear selection immediately felt positive. I cleaned off the old sealant, applied Blue Hylomar to both sides, waited for it to dry a bit, reassembled the covers and took the bike for a run. The gearbox is now GREAT!
Richard Clamp has been as upset about this as me. He even offered to drive down and take a look at the box on the machine.

A couple of things:

1) A theory about the notorious problem associated with inner gearbox case gaskets on Plunger models (I don't know if this applies to swinging arm models)

I was pondering why the presence of the gasket should make a difference to the selector arm claws. I reckon the problem is because the selector arm being pivoted the claws move in an arc toward the selector cam slots. As the claw approachs the edge of the selector cam slot they must be very close to the top edge of the slot. The gasket thickness must be enough to cause the claw to collide with the cam rather than going right into the slot. When the claw is properly positioned into the slot I'm sure there is really good contact. I've made a drawing to try and show my thoughts on this.

2) When adding oil to your gearbox do not stop when a little oil comes out of the level plug. The level plug is in the outer case which fills quicker than the main gearbox casing. Wait for the oil to stop dripping and then add some more, wait a while, add some more etc. until a real stream of oil issues forth from the level plug hole. I'm pretty sure that that is how I allowed my gearbox oil to become so low.

[duTch]

 

............, reassembled the covers and took the bike for a run. The gearbox is now GREAT!

 You had me at no mention of adding oil 

 

2) When adding oil to your gearbox do not stop when a little oil comes out of the level plug. The level plug is in the outer case which fills quicker than the main gearbox casing. Wait for the oil to stop dripping and then add some more, wait a while, add some more etc. until a real stream of oil issues forth from the level plug hole. .......

 Or me being a lazyarse leave the level plug in and add most of the oil, wait a bit then take out the plug and add the rest ? Actually, when I last did it the other week, I didn't even bother with the level plug- just added 400ml from empty, it comes to just about the top of the layshaft (looking in through the inspection hole)

[coater87]

 Great drawing GB!

 It looks perfectly feasible, you would be changing the center to center distance on the claw and on the selector arm with a gasket. Its hard to imagine this center distance would be so critical that a .020 gasket would put the whole thing down. But obviously it works perfect without a gasket, and not at all with. Its got to be the answer.

 Lee

[Greybeard]

I was trying to understand how a few thou could affect the gearbox so dramatically. With a gasket the claw must be just missing its slot, without the gasket it is able to enter. My picture is obviously not accurate but in essence I believe that's what's happening.