mono drive shaft question

[frank1200]

i have just got my hands on a 82 r80g/s
when i let the clutch lever out if gives a good clunk at the gearbox end
it is engaging gears perfectly (or as good as any old bm can) and once moving it does not clunk when changing gear
if i let the clutch out very slowly it does not seem to do it either.
as i assume it is in the driveshaft,is it possible to check the front joint without removing the whole shaft.or do i just go out and pull the shaft out for a look
thanks in advance

 

[PW Cymru]

You can pull back the rubber gaiter between the gearbox and swing arm to look at the U/V joint. Access isn't great but it may give you a clue as to whats causing it.

 

[cookie]

my 86 g/s does a very similar the same thing. it can clunk just after the clutch lever goes fully out & the bike is already moving.

i had the gearbox out & checked the clutch/lubed splines. also changed the clutch thrust bearing. the clunk went away.

within a few hundred miles, it came back. i just ignore it now.

i had my suspicions that it was the drive shaft shock absorber riding up the ramp and then springing back, but now i think it just the action of the clutch.

ok, i dunno what it is but i've had it all apart & there's nothing amiss. it's not very noticeable, and if you don't drop the clutch, it's fine.

they don't all do it though.

see previous post

 

[frank1200]

ok think i will carry on and see if it gets any worse,i also have rob farmers old g/s pd here and it does not seem to do it
and to think i just sold a para with a good drive shaft and may have bought a mono with a dodgy shaft
it could only happen to me
bike is taxed till july so might have a look at it next winter when i will have it in the shed for a tidy up
just going to enjoy it for now

 

[Rob Farmer]

Frank,

This isn't uncommon and gives a nasty knock when you first put the bike under load. The noise echo's through the gearbox and is hard to pin down.

At least with the mono they use the same driveshaft as the twin shocks so you can pick them up cheaply.

The gearbox in your other G/s had a full rebuild that included the shock absorber spring and a new input helicoil gear.

 

[frank1200]

that could do it all right sorry but i have to ask the question which shaft is that
and do you think its ok to keep riding with the way it is or should i look into it now
in other words if i leave it alone till next winter will i do any more damage by riding it
thanks

 

[Rob Farmer]

That's the input shaft

Fits in the hole in the centre of the gearbox and feeds into the clutch

That's the inside of your gearbox BTW

If it was me I'd check it ASAP. It isn't a big job. If you need a replacement then an 81 onwards will be ok - http://cgi.ebay.co.uk/BMW-R-series-...rcycle_Parts&hash=item19c29af2b8#ht_500wt_922 you do need to know if it's the gearbox or driveshaft though.

With a bit of ingenuity you can split the drive shaft using a large vice and a bearing splitter (or a metal plate with a hole in the middle)

 

[frank1200]

thanks rob

 

[frank1200]

ok so i have removed and split the drive shaft and while there is a fair bit of wear in the shock absorber cam in the drive shaft a new cam is (ouch)£150 or a second hand one in motorworks for £40
if i start the engine and engage the clutch with out the shaft connected will i be able to check if the noise is coming from the gearbox

i will post a pic of the cam
so what ya think guys gearbox out tonight or night by the fire

 

[cookie]

do keep us informed how you get on. having ridden another g/s this morning for comparison, i've decided to pull my gearbox and drive shaft again once my ramp is clear of the guzzi gearbox* rebuild i've nearly finished.

how did you compress the driveshaft to split it?


*GT850/Eldorado in case anyone's interested.

 

[fayeslane]

do keep us informed how you get on. having ridden another g/s this morning for comparison, i've decided to pull my gearbox and drive shaft again once my ramp is clear of the guzzi gearbox* rebuild i've nearly finished.

This happened to me when I bought my Mystic, prior to that I thought the GSPD gearbox was OK. Now looking at a rebuild over winter (It's not unusable it just could be better).

 

[The Other PaulG]

Please keep us updated - my '83 G/S does just the same, has done for a fewthousand miles and seems fine, I'd just rather know!

PG

 

[Damien]

Hi Frank,

I have an '86 mono that you are welcome to compare your own against-good excuse for a spin!

How did you split the shaft by the way?

Damien

 

[frank1200]

Hi Frank,

I have an '86 mono that you are welcome to compare your own against-good excuse for a spin!

How did you split the shaft by the way?

Damien

i have a real nice r80g/s pd 1987 that i bought off uglybugga about 6 months ago,it had been rebuilt by rob farmer who had it for a few years before that
as it is a really nice bike i got a chance and bought a 82 g/s which seems a ok bike but original (read nearly 30 years old and never restored so could do with tidying up a little)for green lane and light off road use and to save the pd from the real hard stuff.
the pd with a rob farmer rebuilt grarbox is quite and smooth where as the g/s gives a big clunk when i release the clutch
i was going to keep riding and do a rebuild/light restoration next winter but as posted already thought it would be safer to investigate now

as for splitting the drive shaft i got 2 lenghts of treaded bar and made a plate to go at the end then applied presure form a bearing pullers i had at work
came apart handy enough that way
there is wear in the coupling on the shaft but not enough for the clunk i am getting
nearly had the gearbox out last night but i had left the manual at work along with the haft and did not know to move the engine forward to get the gearbox out

as for an airhead spin would be up for it most any time

 

[cookie]

i never moved the engine to get the gearbox out of mine. comes out fine with it in place

 

[Rob Farmer]

You don't need to Move the Engine Frank. If the swinging arms out Just take the clutch pushrod out, Pull the gearbox out and feed it through the left hand side of the bike. 1/2 to 1 hr should see it sitting on the bench

I usually leave the swinging arm in place and just take the two pivot pins out.

 

[pete.keys]

there is wear in the coupling on the shaft but not enough for the clunk i am getting

What does the cush drive bit look like? If this is worn then this can clause a "clunk" when you let the clutch out in first

The one pictured here is good

If the surface near the "green spot" doesn't look like this and has been worn away then this may be your problem

cheers

-Pete

 

[frank1200]

You don't need to Move the Engine Frank. If the swinging arms out Just take the clutch pushrod out, Pull the gearbox out and feed it through the left hand side of the bike. 1/2 to 1 hr should see it sitting on the bench

I usually leave the swinging arm in place and just take the two pivot pins out.

right watch this space

 

[frank1200]

What does the cush drive bit look like? If this is worn then this can clause a "clunk" when you let the clutch out in first

The one pictured here is good

If the surface near the "green spot" doesn't look like this and has been worn away then this may be your problem

cheers

-Pete

compared to this one my cush drive might be worn more than i thought

 

[frank1200]

right thats the box out it seems so easy when you think about it (and get a little advice)
think this going to work in the shed after half ten at night is a bad idea
still now i get to open the gear box for a little peak
anything i need to watch out for