Clunky First to Second Gear Change

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iandj

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Greetings All

I have a conundrum that I hope someone will have an idea for a cure

I had the gearbox on my 1993 R100GSPD rebuilt before we went away on an Americas trip last year. The bike had done 120,000km and this was the first time the gearbox had been taken apart. All the usual parts (Bearings, return spring etc) were replaced. It was done through a dealer and the guy who did it has many years experiences on airhead bikes. He has diagnosed a couple of other obscure problems that I've had in the past so I trust (famous last words) he would have done a good job. I specifically asked that he replace anything to make it as near new as possible.

Before it went in for the rebuild changing from from first to second gear was usually very clunky, other gear changes were fair

After the rebuild it changes gear beautifully in all gears when the engine/bike is cold but after it warms up I still have a clunky change from first to second gear but all other changes are smooth.

My question is what could be cause the poor first-second gear change after the bike warms up? Worn Selector or other part? Incorrect shimming somewhere? Something else?

I agree it could be poor gear change technique on my part but it is fine when cold. Also very occasionally (1 out of 20) it will change smoothly when hot and I'm not doing anything different.

I intend to go back and see if it can be fixed but I'm looking for ideas and suggestions before spending more money.

Thanks for any help

Ian J
 
iandj said:
Greetings All

I have a conundrum that I hope someone will have an idea for a cure

I had the gearbox on my 1993 R100GSPD rebuilt before we went away on an Americas trip last year. The bike had done 120,000km and this was the first time the gearbox had been taken apart. All the usual parts (Bearings, return spring etc) were replaced. It was done through a dealer and the guy who did it has many years experiences on airhead bikes. He has diagnosed a couple of other obscure problems that I've had in the past so I trust (famous last words) he would have done a good job. I specifically asked that he replace anything to make it as near new as possible.

Before it went in for the rebuild changing from from first to second gear was usually very clunky, other gear changes were fair

After the rebuild it changes gear beautifully in all gears when the engine/bike is cold but after it warms up I still have a clunky change from first to second gear but all other changes are smooth.

My question is what could be cause the poor first-second gear change after the bike warms up? Worn Selector or other part? Incorrect shimming somewhere? Something else?

I agree it could be poor gear change technique on my part but it is fine when cold. Also very occasionally (1 out of 20) it will change smoothly when hot and I'm not doing anything different.

I intend to go back and see if it can be fixed but I'm looking for ideas and suggestions before spending more money.

Thanks for any help

Ian J
Click to expand...


I can't claim to be an Airhead gearbox expert (That's Rob Farmer's job :D ), but I have rebuilt them.

The box on my '89 100GS used to make a noise like a crate of milk bottles being dropped when engaging first gear.

When I re-built it I was very careful about shimming, new bearings, new seals and springs and the condition of the selector forks and dogs. All seemed fine.

I did, however, replace the old nylon 'Indexing Roller' with an SKF bearing, as reccommended in a US site.

I was disappointed to find that the 'new' box was very 'notchy' and difficult to get into first or second - my dream of silky smooth changes was shattered.

About 1,000 miles on its a lot better, so presumably even a re-built box needs to bed in.

I did notice a small amount of wear around the edges of the slots in the cam plates, so maybe I should have replaced them.

I recently re-built my spare box and found it very tight no matter what I did on assembly. Its currently being used by another Club Member and I will be interested to hear how he got on with it in France.

These things are fairly simple and very robust so I guess we just have to accept their 'agricultural' design and be grateful.

Re-reading your post, you seem to have a different issue to me. Mine is 'clunky' when cold but OK when hot.

yours is the opposite, which sounds like a variation in the shimming clearance. As the box warms up the clearances will increase and with an 'optimum' clearance of 0.05mm it doesn't take much heat to vary it.

I'm afraid you may find that if someone else shims it you will have a problem when cold instead :blast

Maybe someone else has a perfect Airhead box, if so I'll be very interested to hear how they achieved it.

Bob.
 
I have a rebuilt gearbox and first gear is a tad taxing to engage at times...only because it is new !
All the gs's have clunky gearboxes ( when I get off one of my Jap bikes and get on the GS I think the box is aboutr to explode :eek: ) it is just the way they are designed :thumb2 Obviously regular oil changes make the gearbox behave a lot better..it is amazing how quickly the sae 80/90 ( whatever ) goes off !!!
 
I would be more than happy if I had the clunky changes only when cold but I have what I have. Thanks for the detailed replys it gives me food for thought. Someone did suggest trying to use synthetic gear oil (Castrol Syntrax) It didn't improve anything much and it started to weep from the gear lever seal.

Anymore comments are welcome.

Regards

Ian J
 
On the way home from buying my 100gs, the gearbox went belly up. Usual output shaft inner bearing. I decided to fix it myself, never having done one. followed Haines and replaced all the bearings and seals but didnt know about the shimming. All went back ok and eighteen months on its still fine and I have to say its probably as smooth as any bm box Ive ridden in some thirty years. Now the bike has done close on 100000 miles so maybe it just takes time to get perfect ......:rob Cant think why yours gets worse when its warm though.
 
. .

. .as Leonard Cohen sings "There ain't no cure for Love" so there ain't no cure for WMB graunchy gearboxes . .
 
Compared to my old Moto Guzzi (now sadly departed) my GS box feels like a GSXR hot all cold. Still makes a noise like a hovering helicopter when in neutral and warm though!!! Pull the clutch in, Ahh silence, let the clutch out and hope that no Vietnam vets nearby suffer a flash back. No worse than any other airhead though.
 
I find preloading the gear lever before pulling in clutch helps a lot, especially engaging first when cold.
As others have said, it's basically a 1922 gearbox thats got more crowded over the years, from 3 to 5 gears.:rob
 
I DID NOT put fecking water in it
I topped it up with Repsol EP90 in Spain, but it was a notchy bitch and was not finding neutral, So I asked the GURU to sort it !!
I might have known I'd have had the piss ripped out of me :rob:handbag
 
Proff said:
I DID NOT put fecking water in it
I topped it up with Repsol EP90 in Spain, but it was a notchy bitch and was not finding neutral, So I asked the GURU to sort it !!
I might have known I'd have had the piss ripped out of me :rob:handbag
Click to expand...

Are you sure? It is an easily made mistake to the untrained mechanical eye !













Door = slam!!
 
clutch adjustment does make a big difference - St. Eptoe has covered this in a few threads here. :thumb2

now....
i read this in a hurry - so maybe i got it wrong :augie but....
did Proff p1ss in his gearbox:confused:

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:hide


:green gri
 
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