bmw R80 scrambler project

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well thats the boxes done,

new/really old steel mudguard added as well, for extra awesome,









from the back,  the panniers/ammo boxes are just a touch wider than the heads, so thats good,

i could probably get them the same width with a bit of a design change, but that'll do me

ammo box/crash protection :D





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ok, well as some of you know, on my way to do my euro trip i blew the gearbox coming into stormin the castle, so i ditched the beemer and bought a bandit12 to do it on,
fast foward to a few weeks ago when i finally got round to picking up thebmw and dropping it off to a local guy who is an expert on air head boxes,  he has dozens of them and they get sent to him from around europe to do, luckily he agreed to do mine as he had nothing on,
and didnt even want to get paid for the job,
just pay for parts,

so here is his write up on the job

I had a quick look at the bike after you had gone. That box sounds as though its got a really serious problem, I've never heard a noise like that before. It will be interesting to see what happened (I'll post pictures).

I was out with horses today and tomorrow I've got to sort out a neighbour's chainsaw before doing anything else but hopefully I'll make a start at getting the box out.

I'll report back on progress.

Just to remind you, this is what turned up:



It was very difficult to push about as the box wasn't running free in Neutral, this was accompanied by horrible 'clunking' noises.

Pretty soon it was a sorry little Rat Bike


Taking it apart wasn't difficult. The tank was held on by the single fuel pipe and the airbox only had one bolt - which was very loose. The seat was clinging on with two nuts that were just started on their threads

The air filter is a scrapper :blast.

Anyway, the box was soon on the bench:


The Output Flange nut came off OK, but the taper was very tight (a good sign).



The box was very dirty around the clutch end. The clutch lever was very stiff so I was expecting trouble there.


The magnetic drain plug didn't look too bad - which surprised me as I was expecting more swarf than this:


Soon the box was apart to reveal . . Swarf everywhere





I can't show it in stills, but the rear bearing on the output shaft was the worst I've ever seen - its almost possible to remove the outer track from what's left of the balls and cage. The other bearings are shot as well - but are not as bad.

The output shaft has been pulled back from the front bearing. There shouldn't be any discernible space between the bearing and the fifth gear pinion. This is why we fit circlips to the front of the inner bearing


The swarf has contaminated the oil and has worn the two bearing sleeves that the first and second gear pinions run on - The plain sleeve for First Gear:


The First Gear pinion has a plain thrust washer on each side. The inner one has been pressed into the Third Gear sliding pinion - its supposed to be flat. This has further damaged the bearing sleeve that did the damage to it.


The (expensive) roller Bearing on the front of the Input Shaft is usually OK, however, this one is jammed solid and the rollers won't turn so I guess its full of swarf


I think the box has run low on oil at some point in its life (there was oil in it when I drained it) as the Input and Output shafts have been 'blued' with heat where the bearings have been choked with swarf:



I'm not intending to replace them as the bearing sleeves will be renewed. I can't see them going soft (or brittle) with the heat treatment.

Some of the retaining washers and circlips on the Output Shaft are damaged and will be replaced. One circlip has been reduced to almost half its circumference, yet I didn't find any broken pieces


The 'clunking' noise heard when the bike was being wheeled about came from the Drive shaft. The rear bearing on the Output Shaft was so worn that the Drive Flange was hitting the outer sleeve on the rear gearbox cover - where the 'boot' attaches. This movement allowed the Worm Drive on the Flange to chew-up the Speedometer Drive gear - you can see how the spline teeth are now tapered towards the lower end. I have ordered a 'Good used' one from Motorworks.


Worse, the Drive Flange has cracked the rear cover. Its not critical and I'll put a touch of Epoxy adhesive on it. A 'Good Used' rear cover is £110 from Motorworks



The good news:

There is some. The selector forks are fine with just one tip showing signs of heat. They will go back in OK.


The complete Selector Mechanism is also A-OK. I'll replace the springs and Indexing Roller as a matter of course but this is actually better than some I've seen



The cam faces on the Input Shaft Shock Absorber are also very good.


The Clutch:

The Clutch assembly looked well past its sell-by date and I wasn't very hopeful about saving all of it.


I removed the six 'hold down' bolts and expected the outer retaining ring to fall off and the Friction Plate to fall out . . . not a bit of it, the thing was welded together and nothing would shift it.

I soaked the three locating pegs in Penetrating Oil and left it for a couple of days - still no movement. So with a gas torch and a hammer and cold chisel (to use as a wedge) I eventually got the bits separated.

The Friction Plate is just down to the rivets and the rest is rusty and seized. I'll save what I can but I have ordered three new parts from Moto-Bins today.



The problem then was that all the components were contaminated with very fine metal swarf and I didn't want to put anything back in that state. Washing the Gear Pinions in Kerosene didn't remove the swarf so I dug out my 27 litre Ultrasonic Cleaner





After two 20-minute sessions, the cleaning fluid was a dark brown colour.


When the fluid was drained the bottom was coated in particles - mostly steel swarf. I cleaned the tank out with a large clump of paper towel which came out covered in sparkly bits.


As the gear pinions and so on were now thoroughly de-greased I carefully re-oiled everything and set it aside ready for assembly.

I have a couple of (large) orders outstanding with Moto-Bins and Motorworks so assembly will have to wait until the shiny new bits have arrived.

To be continued....


I fitted the centre track from a 6403 bearing onto the Output Shaft and then stuck it in the lathe.

Using a carbide strip ground down to a shade over 1mm thickness and given a cutting tip, I cut a circlip groove into the forward end.


It doesn't take long and a new circlip fitted OK.


Then a van arrived . . Oooooh, shiny bits


Hmmmm, doesn't look like £432-worth does it



It's not all for this bike as I'm re-stocking some of the small stuff :D.

New vs. Old.



The second gear bearing sleeve was a nice tight fit on the shaft.


Always ensure that these oil holes are lined up as there isn't an oil groove on the inside of the sleeve.


The new 'High Fifth' gear was fitted, along with fourth & Second gears, front bearing and the all-important circlip. Second gear is a lovely fit on that new sleeve - smooth without any hint of play



I then added the third and first gear pinions. First gear is also a nice smooth fit without shake on its new sleeve - quite unlike the way it was when it came off originally.

The 'Standard Fifth' gear is shown, there is no difference in diameter they just cunningly re-profile it to include fewer teeth


I built up the Input and  Intermediate shafts yesterday, but didn't take pictures (it involves spring compressors, various home-made steel 'dollies' and my floor press) all three shafts are now ready to go back in. The Gear Selector mechanism is also ready with new springs and Indexing Roller.


I may get the box assembled tomorrow but then there will be a short break as I'm off to "The Bristol Classic Bike Show" at Shepton Mallet on Friday/Saturday. I won't be on the 1150GSA this year as I don't fancy the M6 on a Friday with snow and ice :-o - I'll be taking a large 4x4 8). I must be getting old and soft

I put the gearbox casing through the Ultrasonic Cleaner yesterday. It is clean but the alloy is now dark and mottled. I'll see if I can clean it up with something before building it up.

To be continued . . . .


More progress to report

Having assembled the three shafts I heated the gearbox case with a Propane torch and fitted them along with the intermediate shaft selector fork that has to go in at the same time. There are two oil baffles in front of the Intermediate & Output shafts and the Input shaft's roller bearing has to go in before the others as all three bearings are an Interference fit. It entails a bit of juggling and one has to be quick.

A quick tap with a rubber mallet ensures that all bearings are seated before the case cools.

Then the Selector mechanism, Output Shaft Selector forks and shaft and main oil baffle are fitted.


When the case has cooled the gear lever if fitted and the gearchange is checked. It isn't great with the rear bearings unsupported but as long as all gears can be selected it will be OK when the rear cover is fitted.

Then the rear cover gasket goes on with a light smear of Blue Hylomar.



And now for the technical bit - Shimming the end-float :-o.

One needs a 'Shimming Plate' for this job:


I have drilled mine so that I can bolt it down on top of the gasket. I think that this gives me the most accurate measurements but people have different approaches and may just rest the plate on the case or put the gasket in after the measuring has been done - each to his own.


I use a 'Outside Micrometer' and a 'Depth Micrometer' for this job.

First measure the thickness of the Shimming Plate:


Then measure the thickness of the oil baffle that goes on the rear of the Intermediate shaft:


Using the Depth Micrometer, measure the height of each bearing above the plate - I take about six measurements around each bearing.


Then measure the depth of the bearing housings in the rear cover - again, I take about six per bearing.


All of this is written down and then the shim thickness is calculated for each bearing:

The formula goes . .

(Depth in cover - 0.05mm clearance) - (height above plate + plate thickness + baffle thickness) = Shim thickness.

One then has to assemble a collection of shims to the right value. These come in four nominal sizes - 0.20mm / 0.28mm / 0.38mm / 0.50mm. However there is quite a variation and I spend time mixing & matching until I get the right result to within 0.02mm.

Here, I am looking for 0.95mm for the Output shaft and the shims measure 0.94 - good enough for me ;).


The collection of shims are lightly greased and placed centrally on the bearings - you don't want them moving as the cover is fitted


I screw four 6mm studs into the back if the case as a guide for the cover. It will be hot and if fumbled causes mayhem with shims falling about the place :-o.


A final check is made of the rear cover to ensure it is flat. If not it will cause problems.


And then the cover is heated with the Propane torch and carefully lowered onto the bearings. It is then tapped down with a rubber mallet and five of the nine set screws are fitted.


The studs are removed and all set screws fitted and torqued-down to 9 lbs/ft.


When the box has cooled and I am happy that the clearances feel right I fit the three oil seals. First the input shaft splines are masked and the shaft given a light smear of grease.


I use a long socket of appropriate size to seat the oil seal into the case. The seal is given a light coat of Blue Hylomar to ensure its oil tight around the case.


Surplus compound is wiped away and that's one done :thumb.


Now remove the gear lever and repeat the process with the gear lever shaft oil seal. I used an 18mm socket to seat it.



The gear lever shaft is given a light smear of grease and replaced.


The Output Shaft oil seal is given the same treatment. This is a Monolever bike so the oil seal lips face outwards to let the box breath into the leg (which has oil in it). Paralevers have a different oil seal that is faced inwards as the leg is dry. Paralever boxes breath through the hollow bolt that secures the speedometer cable and battery earth strap.

I use a flat steel disk I turned on the lathe with a 50mm 3/4" drive socket to seat the rear oil seal.


The output Shaft drive flange is then given a light greasing and fitted to the taper shaft - the taper is kept dry. The nut is torqued down to 161 lbs/ft which is a bit of a heave. I use a long locking bar and a Certified 50-300 lbs/ft 3/4"-drive torque wrench for this.


Almost finished now. The Neutral Switch is checked with a Multi-Meter and fitted with a new washer. The Drain Plug is also fitted with a new washer. I cleaned the swarf off the magnet with cloth and a high-pressure air line (don't try this at home kids :rob).


The replacement Speedometer Drive, a new collar and the breather bolt are then fitted (it doesn't strictly need a breather bolt as a plain one would do but it has one so it went back in).


And that's it - the box is finished . . . .


Now for the clutch . . . .

so thats it, box is done clutch done, bike back together
and a massive parts bill to pay,  almost to the price i paid for the bike a couple of years ago

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fuck yeah he's an awesome dude,  i have to get him something for all the work,  but he doesnt drink, so i can't even ply him with copious amounts of single malt whisky.

i guess ill give him a resturant voucher and some cash.


roughly in parts, just for the gearbox its cost about £400,  ive seen complete "rebuilt boxes" out of germany for £550.  it makes me wonder how you could viably rebuild gearboxes for £150 labour,  seeing the labour bob put into the job,  there must be atleast 15-25 hours worth in there,  and the germans are selling the boxes, not even a swap,

a second hand box of unknown condition costs roughly £250-£300  soo you only have at best 300 to play with for all the parts and labour!!


any way, 

he did the cluch as well,  it took bob 2 hands to pull in the lever :D

i'd just assumed was a bmw dry clutch thing,

I had employed my massive forearms to better effect :D  but this wasnt right, so bob got on the case and fixed that,  along with all the rest of the dodgy bits on the bike that i didnt give a shit about but bob woth his O.C.D. couldn't live with,

i think it was driving him mad that i wouldnt let him paint the tank



ill get some photos up when i grab the bike

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Well, where was I . . Oh yes - the clutch.

All the new parts (plus one old one) were laid out:


I then de-greased and washed the flywheel and housing as well as I could with Industrial cleaner and hot water (DOH, I should have set the camera 'white balance' to "Daylight" :blast).


I used 'Optimol TA' on the splines and spring contact points before assembly to make sure that everything moves smoothly.

Its just like a car clutch and the friction plate needs to be centred before the cover plate is tightened down. I used a spare Input Shaft with the pushrod pushed through to the diaphragm spring to align everything before the 6 set screws are tightened down evenly to a final torque of 17 lbs/ft.


The Input shaft is then withdrawn and the gearbox installed. I had removed the swing arm to make this easier.


With the gearbox installed (the splines lined-up OK, thankfully) The airbox goes on - this is not a nice job as the two upper bolts are a fiddle. I should have ground a 6mm Allen Key down a bit but decided to just take my time over it.


Notice anything missing . . .  Yup, I forgot to put the cross-over fuel pipe in so it all had to come apart . . Bummer :blast.

The clutch operating arm is then installed and set to the requisite 203mm clearance from the cable mounting lug (The BMW Club had long articles in their mag about this :augie ).


I thought I'd better put a new Air Filter in while I was at it :rolleyes:.


The rear brake stoplight switch looked a bit past its best - but it works :thumb.


The swing Arm was installed, centred and torqued-down. A new Speedo Cable boot was fitted in place of the hard and cracked one and everything started coming together.

I remembered to fill the gearbox with oil and while I was at it checked and topped up the bevel drive and drive shaft. The engine oil was nice and clean so didn't need touching.


Then the rear carrier, tank, seat and silencer (:confused:) were fitted. This involved bad language and a lack of photographs but finally here we are . . . .

The Rat Bike Lives :bounce1  :clap.







so thats it, got the bike back today,
ride home was interesting,  would only fire on one except at idle or with the choke on,  so i rode home on the choke :D  still managed 65mph with the new higher 5th gear just on choke :D

clutch is super easy, easier than any of my other bikes in fact,

to do jobs are,  unblock main jet,  replace all the cables,
balance the carbs,  do the valve clearances, tighten the rocker arm end play, replace the indicator relay with a led unit,   then start the rear  spoked wheel. and come up with a steel front mud guard

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well its been a couple of years and ive done bugger all to the bike,
after the gear box was done, i literally parked it up and have not started it since.  as punishment for blowing up on me in the first place :D

i got the tank painted about a by my workmate and told him to do what ever he wanted.
and this was the result

a nice copper pearl type... thing in the paint, all flickery and shit.
awesome job i must say,

i pulled the carbs off and replaced all the jets and gave them an ultrasonic clean, replaced the diaphragms etc

i also decided it was high time i ditched the master cylinder, (as its set up for a twin caliper front end)
in order to do that i needed to replace the throttle, starter button and master cylinder,
which also gave me the opportunity to re-design and custom make some new throttle cables with a 90' bend into the carb so it avoided the exhaust


im waiting on a new/2nd hand ignition switch because some little tard tried to steal the bike, not realising that it had no gas and none of the fuel lines were connected, the little fucks did get away with my ktm super moto though :( fuckers

any way while im waiting on the ignition i though i best see if this old dog would start after 2 years of just lazing about, like a gypsy bum on the dole

see here for the results ....

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cleaned up all the wiring,  replaced the lighting relay, and the indicator relay,
led indicators got added to front and back,
the rear light has them built in, but they were a little to close together for my liking,
old front ones were shit, so got replaced as well,

have added waterproof plugs for the new digital speedo thats on the way from the fatherland. so that'll just be a matter of adding the plugs to the speedo loom and she'll be plug and play.


had to also replace the ignition switch, from last time some little chavy prick tried to steal it

ummm balanced the carbs,

need to order a front brake switch, hobble together some sort of front mud guard, and she'll be good to go for a mot (wof)
 i think ill go for a fang tomorrow and do a oil and filter change,

i also have a leaking final drive, so that'll have to be fixed at some point

glory shots




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right got the speedo all hooked up,

bike is running pretty good although runs out of gas at high sustained revs because of the stupid floats,

ordered a set of plastic ones out of the states to replace the shit foam ones that sink,  fucken bing and their stupid ideas,

took the bike for a mot (wof) on friday and it went through no bother,

heres a shit video of a wee thrash,

had to hold the camera in my mouth so...


ill keep ya posted,  have also front mudguard to go on at some point.  and a leaky fork seal (gayest job on a bike)

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yeah dunno whats up with that, its the stock signal that the bmw clocks got,

i could try the signal from the other cylinder i suppose and see if thats cleaner.

also have to replace that shit start switch as well.

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Ooh I like the key location might have to steal that idea should simplify all the wiring being in the one place, is it a aftermarket key barrel?

my Honda has a stupidly long key barrel to get past all the plastics that are no longer there

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stock location for some models, 

handy because alot of the wiring can be hidden in the headlight :D


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With photo bucket not available is there another source for the pictures. I like the detail you have presented here, some pictures would be good to see, cheers

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