Well, following on from my intro post, I thought I would throw up a build thread, considering I'm going to need help along the line, so I might as well document the process.

I picked up my first BMW K100 84' yesterday, old bloke had it sitting in his shed for 5 years unmoved, he couldn't tell me what was wrong with it other than it had been sitting for that long. But on inspection, it had no brakes, leaking rear m/cyl, possible leaking rear main seal, and a couple of scuffs where he had dropped it.



I got it home and immediately started the process of trying to get it running, so replaced stale fuel, new battery, and it turns over fine, but it went downhill from here, I noticed a fuel leak, which was a broken cap on the elec connections. Then the fuel tank was full of black shit, pulled the fuel pump out and the rubber mount has deteriorated beyond saving, the fuel pump was clogged up with the black gunk from the rubber, so I turned my attention elsewhere, taking the injectors out, I noticed years of oily mess build up, so I'm willing to bet it was parked up with a full tank of fuel, and over the next 5 years it proceeded to leak over the block, attracting all forms of foreign rubbish.



So my plan is, clean the injectors, find a replacement fuel pump assy, or even just buy a complete second hand assy with a tank if I have to, and then try again to get this thing started.




In hindsight, I may have made a mistake buying this bike, but I'm sort of committed to repairing it now.

A direct copy fuel pump is available from Aliexpress for about $37.00 Au from Global Autoparts.https://www.aliexpress.com/item/for-BMW-K-Ducati-K75-K100-K1100-K1-1983-1997-BOSCH-16121461576-16121460452-0580-463-999/32784411992.html? I've been running one for over 12 months no problems. a complete Chinese rear master cylinder that fits with minor modifications $13.33 Au. The supplier I got mine of no longer exists however there are heaps that look the same.
https://www.aliexpress.com/item/Motorcycle-Rear-Foot-Hydraulic-Brake-Pump-Refit-Rear-Brake-Master-Cylinder-Pump-For-Suzuki-Kawasaki-Honda/32922240225.html?spm=2114.search0204.3.285.6c6c3d880O3vSw&ws_ab_test=searchweb0_0,searchweb201602_3_10065_10068_10130_318_10547_319_10546_5727220_10548_317_10696_450_10084_10083_10618_452_535_534_10307_533_532_10131_10132_10133_204_10059_10884_10887_100031_320_10103_448_449_5727320,searchweb201603_1,ppcSwitch_0_ppcChannel&algo_expid=22ca7e45-6f37-4a95-9ee6-96a539c952d9-38&algo_pvid=22ca7e45-6f37-4a95-9ee6-96a539c952d9&transAbTest=ae803_4&priceBeautifyAB=0

Regards Martin

When it's running it will be bombproof, but nothing (okay: very little) survives being parked up like that. With a K of that age, you also need to be looking at replacing all the rubberware down by the throttlebodies. This lot:

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=40&Ct=FA&SbCt=BA_15_40_FA_50&spPage=2

Items 1, 4, 5 and 6. And item 1 here:

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=40&Ct=BA&SbCt=BA_15_40_BA_25

Especially this as it will be split. Apart from the pump that Martin mentions, you will need external fuel line (source locally), internal fuel line and a fuel filter - items 1 and 8 here:

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=40&Ct=FA&SbCt=BA_15_40_FA_40

Do not try to use external line inside the tank as it WILL rot away. Make your external fuel lines between two and three inches longer than standard as it will make removing/replacing the fuel tank a lot easier.

I had to do all of this on mine and so far it's done 61,000 almost trouble-free miles in my possession and 101000 miles overall.

Well, I got it running! Even rode it around the backyard, but she's got no brakes front or rear, so 2nd gear got a bit hairy lol.

I ended up buying a pump kit from EME, everything I needed and the price was fair. I cleaned the injectors myself to save some coin, one of them was possibly blocked, as it took a few goes to get a flow coming through. 
And this is the result!

Nice! I think you'll have an easier time putting the old girl back into service than you had initially thought.  

brickrider2 wrote:Nice! I think you'll have an easier time putting the old girl back into service than you had initially thought.  

I'm not out of the woods yet unfortunately.

It blows a bit of smoke, even after an oil change, it's white, so I'm thinking it might need a head gasket, I'll have look into that further down the track, as I need to get these brakes working next.

I tried bleeding up the front brakes, but I get nothing, so I thought I would go the other way and push fluid up to the m/cyl, but it seems to be blocked, the brake lever moves easily and freely, so I hope I'm right in thinking the calipers might be seized up?
I want to used compressed air to try and un-seize them, but my compressor died about a month ago, and my new one is still a week away, I wonder if I can pump it full of grease to free it up?

I've ordered a cheap rear m/cyl, hopefully that gets here next week.

it looks like if the grease trick doesn't work I'll have to pack it up today. I was going to clean all the crusty fairings that came with it, but the weather has turned here, so that's off the cards as well.

Blacktop wrote:I wonder if I can pump it full of grease to free it up?

Don't. You'll contaminate i.e. destroy the entire system.

The master cylinders get a build up of crud at the bottom end and the piston has been pushed there and wont return so a short blast of compressed air with a few layers of cloth to catch the piston should do the trick but first remove the small Allen head screw so as not to destroy the piston on its return journey.

RicK G wrote:The master cylinders get a build up of crud at the bottom end and the piston has been pushed there and wont return so a short blast of compressed air with a few layers of cloth to catch the piston should do the trick but first remove the small Allen head screw so as not to destroy the piston on its return journey.

I'll give that a go when I get my compressor.

Let's see if you can spot the problem I had trying to pull apart the calipers

Where's the bleed nipples? Oh aye - and the rounded-off allen bolt. Good piece of camoflage there

Dai wrote:Where's the bleed nipples? Oh aye - and the rounded-off allen bolt. Good piece of camoflage there

I've got a long Allen key and I put a spanner on the end of it after I heated up the housing with a blowtorch, and it still didn't budge! 

Luckily I had just bought a MIG welder on Friday,   so I had to weld a nut on the end of it and get the long ratchet onto it.

I'll be putting it back together with copper anti-seize I think.

Blacktop wrote:

RicK G wrote:The master cylinders get a build up of crud at the bottom end and the piston has been pushed there and wont return so a short blast of compressed air with a few layers of cloth to catch the piston should do the trick but first remove the small Allen head screw so as not to destroy the piston on its return journey.

I'll give that a go when I get my compressor.

Let's see if you can spot the problem I had trying to pull apart the calipers

Your problem is you splitted the calipers. The O-rings between the two halves are very hard to obtain. Reusing the old ones usually end up leaking.

P08 (or F08 if you prefer) overhaul kits come with the centre o-ring. It's the overhaul kits for the 4-pot calipers that don't have the o-ring because you're supposed to  push the pistons out with the calipers intact. Brembo's reasoning was that it's possible to distort the body when you remove the bolts (if you can get the buggers out but that's another story). However:

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=silicon+bs+610+o-rings&_sacat=0

Use silicon, not nitrile or viton. Link to a conversation I had with Inge about this:-

https://www.k100-forum.com/t8678-four-pot-brembos-centre-o-ring-splitting-the-calipers

Dai wrote:P08 (or F08 if you prefer) overhaul kits come with the centre o-ring. It's the overhaul kits for the 4-pot calipers that don't have the o-ring because you're supposed to  push the pistons out with the calipers intact. Brembo's reasoning was that it's possible to distort the body when you remove the bolts (if you can get the buggers out but that's another story). However:

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=silicon+bs+610+o-rings&_sacat=0

Use silicon, not nitrile or viton. Link to a conversation I had with Inge about this:-

https://www.k100-forum.com/t8678-four-pot-brembos-centre-o-ring-splitting-the-calipers

 Great info! I knew i started this thread for a reason 

One of the blokes I work with used to use a lot of o rings rebuilding pumps, he has some contacts so I'll lean on him and see what he can come up with, the EPDM will probably be most cost-effective and easy to find.

I do not recommend cheap copies of fuel pump.
I bought one that died less than a kilometer later. No refund.
Bosch original ones can be found around 100€.

I bought one off Aliexpress paid around $27.41 Au. It's still running strong more than 12 months later. I did a bit of research and went with a manufacturer Global Auto Parts. Another mate is also running one with no problems.
However as a precaution I have cleaned lubed and stored my still good original in the tail. Not all Chinese pumps are the same so it still seems to be possible to get a dodgy one.
Regards Martin.

Dai wrote:P08 (or F08 if you prefer) overhaul kits come with the centre o-ring.

Let's see who is right. Time will tell.

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=40&Ct=IA&SbCt=BA_15_40_IA_30&spPage=2

Item  BRA10493

The o-ring is the small one between the instructions and the grease pouch. For some reason the following item (BRA10310) contains two caliper half o-rings.


Hope this helps put any doubts to rest.

Thanks, it's good to know a supplier that delivers a complete set. The BMW dealer doesn't.

If you ever get stuck for a set of 'BMW' seals for the P08/F08, get a set of Moto Guzzi ones for any of the 850cc or 950cc models from 1972-1998. It's the same piston size, the same caliper shape and comes out of the same factory (Brembo). The castings for the mounting bosses are slightly different, so the BMW one won't quite fit the Guzzi and vice-versa. Easy way to tell the difference is that the mounting bosses for the BMW variant are threaded, but the Guzzi version isn't. But don't go asking me why BMW charge more than Moto Guzzi for the same seals 'coz I don't have a clue...

Ordered the kits from Motorworks. I finally got my hands on a compressor as mine still isn't ready to collect, it didn't take too much pressure before they popped out, but it's just mud in inside!



On the other hand, I'm doing the same thing on my DR600 calliper, that took so much pressure that when it finally popped the cyl put a dent in the plywood table top I'm working on, and almost sent me deaf with the bang it made!

You've ordered new brake pads too? Because those will be toast, as in: the pads will depart the backing just when you really don't want them to.

Dai wrote:You've ordered new brake pads too? Because those will be toast, as in: the pads will depart the backing just when you really don't want them to.

 
I'll get those locally when the kits arrive.

I started cleaning them up with brake cleaner, but they dry yellow, so I'm going to invest in an ultrasonic cleaner and run them through.
I've wanted one for a long time, and I could of used one about 10 times in the last 6 months, so I'm going to bite the bullet and order one this weekend.

On another note, the rear brake master cyl I bought turned up, and appears to be the wrong one, it has a threaded shaft instead of a plunger, and the thread on the output is different, probably my own fault for not paying attention or reading the description when purchasing online, but the itmes they had pictured looked right.

only $17 so no big loss there, just longer I have to wait until I get this riding.