Airhead Gearboxes

[(RIP) philgunn]

Great thread lads

I have a Aquablaster sitting at home (vapourmate 1) , my main constraint is the compressed air I was thinking of going for a road tow unit with between 40/100 CFM should cover my requirments

The pictures and information on gearbox refurbishment is second to none , but being a bit slow i will interject every so often for addational info,

like pulling off the Gearbox cover as an example , i have struggled in the past with the flange removal tool , and of course reshimming the finished unit

Phil Gunn
Cork

projects are mounting up and need work ... NOW

 

[Rob Farmer]

Phill,

There's a small nozzle available for the Vapourmate 1 that alows it to be used with a 10 CFM compressor otherwise it only needs 20 CFM (only!!).

 

[Voyager]

like pulling off the Gearbox cover as an example , i have struggled in the past with the flange removal tool , and of course reshimming the finished unit

Phil Gunn

I made up a couple of tools, plus some spacers, for this job.

First - removing the output flange nut, which is torqued to 161 Lbs/Ft.

The output flange is recessed below the rim that the boot connects to, so a spacer is required to kaap the locking bar clear.

Here are the bits:

With everything bolted up its a matter of loosening the nut with a Power Bar:

The standard tool is a nice, neat unit - but I happened to have a huge Sykes hydraulic bearing splitter, so I made an adaptor plate for it. The spacer has to go below the plate to keep everything free.

Sometimes the flanges just pop off easily, other times I have to use huge force and then tap the adaptor plate with a hammer.

Eventually they jump off the taper.

There are nine socket-headed set screws holding the cover down. Once they have been removed the cover has to be heated before it can be removed.

You will grow old waiting for a hot air gun to heat the cover, so I use a propane torch. It has to be applied carefully, moving it around to warm everything evenly (the picture makes it look worse than it is ). I put a drop of gear oil on the case - it should be runny, but not smoking .

Once the cover is loose you can get inside - Rob has shown what to do next.

One tip; I use four 6mm studs to align the (hot) cover when replacing it over the shims. It should prevent the cover moving and knocking the carefully-aligned shims into the gears (DAMHIK ).

Right - I'd better stop hi-jacking Rob's thread

I'm sure one of us will be happy to go through the shimming process (with pictures).

Bob.

 

[Rob Farmer]

Right - I'd better stop hi-jacking Rob's thread

I'm sure one of us will be happy to go through the shimming process (with pictures).

Feel free Bob, you're doing a great job

 

[Steptoe]

Bearing sizes = for a 5 speed gearbox .

Output shaft - input end 6403 c3 , output end 6304 c3

Layshaft - input end 6304 c3 , output end 6304 c3 ( sealed bearing)

Input shaft - input end NU204E , output end 6304 c3 .

My flange puller toll does both jobs. Hold the flange to undo the (tight) nut and pulls off the flange.

And get hold of an old sandwich toaster to use for heating up any cases and bearings, available at boot sales for a couple of quid. Heats the cover evenly at the same time and saves messing about with naked flames

 

[(RIP) philgunn]

One of the best threads ever

as they say over here

"your playing a blinder"
the info from both of you is invaluable

Thanks for the info on the Vacublaster, I hope to address the commissioning of it shortly ( I keep on saying that ) but with a lot of bikes it takes time to get around all the taskes and chores lined up for me .


but once again , Great work the pair of you

pg

 

[Voyager]

My flange puller toll does both jobs. Hold the flange to undo the (tight) nut and pulls off the flange.

I love that puller and really must get one. So much neater than my conglomeration

Neil, A question for you (or Rob) . .

Why is it that BMW recommend an open bearing on the rear of the Input shaft ??

If you look down the clutch mechanism hole you can see the bearing track:

I would have thought that any dirt getting in from the rear (damaged rubber bellows) or from the front (along the shaft past the clutch pushrod) would go straight into the bearing.

When I refurbished 'Bumpmuncher's' box, he said he was going to do some sand racing - so I put a sealed bearing there, just in case. The inner face wasn't sealed, just covered by the oil baffle as I removed one of the seals.

I did the same with 'Belper Phil's' box as you can see in my photos.

I realise that there is a drain below the bearing that would allow dirt into the oil - but the seal might save the bearing, at least for a while.

Does the clutch operating mechanism require some gearbox oil mist ??? If it does it will still get some via the drain channel in the rear cover.

I can't think of a good reason why the input shaft bearing shouldn't be sealed at the rear face - But I'm happy to be educated

Bob.

 

[brokenbeemer]

transmission shim measurment

The excellent procedure leaves a question. You show the measurement from the bearing inner race to the fixture. Is that correct and do you allow for the C3 looseness of .0762 mm?
Thanks from across the wet.
vince

 

[Voyager]

Do you allow for the C3 looseness of .0762 mm? vince

Vince,

I don't make any allowances for the C3 bearings and I have never heard of anyone doing so.

When using the Shimming Plate to measure the height of the bearing above the gasket on the rear of the box the bearings are not tight.

Therefore, when holding the Depth Micrometer level on the face of the bearing any slack is taken up.

The Depth Micrometer gives the height of the bearing face above the Shimming Plate.

One has to know the accurate thickness of the Shimming Plate (someone not a million miles away has a beautifully-milled Shimming Plate. Mine looks a bit crude by comparison ).

Then one has to determine the depth of the bearing housings in the end cover. With all these measurements I take six or eight around each housing. Naturally they are all different

Then its a case of determining the clearance with each bearing:

(Depth in end Cover) - (Thickness of Shimming Plate + Height of bearing above plate) = Clearance.

(Clearance) - (0.05mm + thickness of oil baffle (where fitted)) = thickness of shims required.

The next problem is that the shims come in four sizes, 0.20, 0.28, 0.38 & 0.50mm. Its not always possible to get the exact combination.

However, I have found that the shims are not always what they seem so I measure the stack with the micrometer. By mixing & matching different shims (sometimes of the same nominal thickness) I can get very close to the required thickness.

So, to conclude, The final clearance on each shaft is 0.05mm regardless of any in-built play in the bearings.

(Unless someone knows different ).

Bob.

 

[Belper phil]

Box

Good to see the pictures Bob , quality.

3500 mls since the re-build, running well and everything as sweet as

Quality Castrol oil added to box after re-fitting

 

[(RIP) Arkwright]

Good write up and pictures Bob, a slight variation possibly, when I did my gearboxes I allowed 0.1mm clearance and 0.2mm for the compressed gasket, then when the boxes were cool, tapped both the output and input shafts with a soft metal hammer before checking that they were not too tight.

 

[Voyager]

I drilled my shimming plate and bolt it down over a new gasket. I hope that gives the final gasket clearance during the measurements.

When the box has been re-assembled I re-heat both ends to make sure that all the bearings are seated properly (it would happen on the road when the box is hot anyway).

Despite all that I find the boxes are quite tight. I have to use an old clutch plate on the input shaft in order to check the gearchange action.

They seem fine in use and soon settle down.

I can't believe that the factory went to all this trouble


Phil . . Thanks for the testimonial



Bob.

 

[seadog]

absolutely brilliant post, must have taken a lot of time to write!!!, well i know where to send my gearbox if i get problems now


cheers
mike

 

[(RIP) Bin Ridin]

My flange puller tool does both jobs. Hold the flange to undo the (tight) nut and pulls off the flange.

Hi, is this available to buy or is it something you had made speshly? Bin

 

[Voyager]

Hi, is this available to buy or is it something you had made speshly? Bin

It sounds as though Neil has one of these - or a copy:

http://www.cycleworks.net/index.php?main_page=product_info&cPath=29_33_52&products_id=321

Bob.

 

[(RIP) Bin Ridin]

Thank you!

 

[Flipfly]

Don't be fooled by your gearbox

It may feel ok, it may change gear as intended, but it's probably one step off failing

Thankfully, mine has just been "bobbed" and I no longer have any of those worries.

Many thanks to Bob and his vast knowledge and all round good guyishness

It will be back in the bike on Saturday and then I just have to wait for Kais to finish the rear shock before I get to enjoy the old girl once more

 

[Voyager]

Don't be fooled by your gearbox - it's probably one step off failing

Yes, Bertha's Box had a few 'issues' .

I've put 81 pictures of the work on Photobucket. I must do a "This is what can go wrong" thread.

Or would that just worry people too much ? .



I'm looking forward to the "Ride Report" when the old girl is back together .

Bob.

 

[Flipfly]

Yes, Bertha's Box had a few 'issues' .

I've put 81 pictures of the work on Photobucket. I must do a "This is what can go wrong" thread.

Or would that just worry people too much ? .



I'm looking forward to the "Ride Report" when the old girl is back together .

Bob.

Let em worry Bob, at least I can concentrate my worry on all the other aspects of the bike I haven't dealt with yet

There's really only the engine (could explode?), the frame (could crack?), the Bevel drive (could lunch itself?), the drive shaft (could fall apart?) and the petrol tank which could melt if the weather gets too hot.
Gonna be great to get the old girl out again, bet the RAC are just waiting for the call

 

[MOLAHS]

Circlip mod

If a BMW workshop rebuilt a 89/90 R100GSPD gearbox would they "retrofit" the circlip ?