My 1985 BMW K100 RS Project

[mark284811]

My First "Build" Project + Build Thread

Who Am I ?

So I'd like to start by setting the tone for who i am and what led me in this direction.

My Name is Mark, and i'm 33. I've been a car guy for as long as i can remember, owning several "boring diesel vehicles" due to travelling higher than average mileage for work. I'm a Semiconductor Project Manager, so whilst I'm not daft, I'm also not the most mechanically / engineer minded.



In my most recent role change, it meant i needed to commute regularly 100+ miles, so i opted to get a motorcycle licence instead of spending money on a season ticket.

For a while i've always had a thought of wanting to take something fully to bits, like i used to with computers, but with a car or a motorbike to get a better understanding of how they all worked, aswell as then eventually doing a project later down the line when my son is older (currently 3).

What is my Prior Experience when "Tinkering" ?

I've had a few weekend Cars (350Z, Caterham) then i started racing Caterhams for a few years, I've always been able to do the usual stuff (oil / filters / brake pads and discs etc) when racing the Caterham I'd do the usual spanner checks on every nut and bolt to check i was safe in the days leading up to a race event.

The Project

So i've jumped straight in and won a Clarke Motorcycle Lift on Ebay to save my back "i know i'm only 33, but it was never going to be fun to bend down all the time to take an entire motorcyle to bits"


I've been looking on the usual locations (Facebook Marketplace "Sigh", Ebay, AutoTrader, Pistonheads ) Usually being too late to the scene or not wanting to spend the money people were asking. In essence i wanted something that was (Ideally classified as "Historic" or nearly there, shaft drive "Just because i thought it'd be more fun to work with", less than £1000 "incase i made a big mistake and screwed it all up"

I'd slowly whittled it down to various BMW motorcycles, R100 , K100 , etc etc

Eventually i found a 1985, 66,000 mile BMW K100 RS a few weeks ago. Price was in the right ballpark..it wasnt quite eligable to be classed as Historic, but close enough.

I went to look at the vehicle and i was a little surprised. It turned out that it hadnt been on the road for 9 years, the bodywork was all damaged in one way or another, it was leaking oil, there was corrosion EVERYWHERE, there was a birds nest in the side fairing where it channeled air to the Radiator... IT WAS PERFECT !

So Naturally i bought it on 15th June 2022.. and here she was in her previous home when the deal was done.



I've stripped it down to it's current state... More posts to come to show how i got to that point, what the inspiration has been for the bike when it comes to an end point, and more posts as i continue my journey. I hope you are interested in following the build thread and please do offer suggestions

Heres a little to wet your appetite

[CouncilFerrari]

That looks great, I did a similar thing over lockdown to a BMW R1100GS and sold it earlier this year;

What are your plans with the bike, restore back to standard or modify?

This fella in the US did a Cafe Racer job on his R100, don't know if it will be useful to you. https://www.youtube.com/watch?v=yCjk0jGQNgY

Motorworks BMW in Huddersfield are great for parts btw.

[mark284811]

CouncilFerrari said:

What are your plans with the bike, restore back to standard or modify?

Thanks, I'm planning to modify it. I've got a few ideas, and I've saved tonnes of photos from the internet from different projects K100's to use for inspiration.

Good shout on a parts supplier.. ironically I've already spent a few hundred quid in nut and bolt levels of mechanical refresh.

[Marquezs Stabilisers]

Are you going to be incredibly original and turn it into a cafe racer or scrambler?

[PurpleTurtle]

Buckles in for the thread!

I love these in a sort of "they're so uncool they are cool" way. I've often found myself checking them on eBay.

I've got three bikes, two in a state of disrepair, wife would kill me if I bought a fourth, so yeah, I'm all over this thread!

[BigFatNinja]

Fantastic! Look forward to watching this unfold

Its a pity we can dedicate a whole section of this site to tts playing mental gymnastics endlessly about non piston related ste arguing like children but no reader's bikes section

[slopes]

Marquezs Stabilisers said:

Are you going to be incredibly original and turn it into a cafe racer or scrambler?

To be fair, with the exception of making it a chopper, there isn't a great deal else you can do with it.

[Speed addicted]

I’ve got a (currently unwell) K100 that got cafed a few years ago, I’ll try to help when the electrical weirdness raises its head!
Have fun

[Marquezs Stabilisers]

slopes said:

To be fair, with the exception of making it a chopper, there isn't a great deal else you can do with it.

I want to see him go all in and build something like this

https://www.topspeed.com/motorcycles/motorcycle-ne...

[mark284811]

Marquezs Stabilisers said:

Are you going to be incredibly original and turn it into a cafe racer or scrambler?

It's a bit tricky to describe, it won't be an authentic "Cafe Racer" as the lines don't really make it a cafe racer, because of the shape of the frame and the way the tank is angled it doesn't have the characteristic that a cafe racer has, which is usually a pretty flat line horizontally.

It's funny though because when people i speak to about the project ask me the style i say "cafe racer" because i don't really know how to categorise it. I think I'll be taking inspiration from the BMW R Nine T though in some aspects which i guess it is sometimes a hybrid between a cafe racer/scrambler depending on which tyres you fit.

In short.. it won't be original... but I'm not sure it'll fit in the above to categories either. So perhaps i just have to go with "Custom" ?

I'll share some photos that are currently inspiring me. It's effectively going to be a smash-up of all of these in one way or another.

[mark284811]

PurpleTurtle said:

I love these in a sort of "they're so uncool they are cool" way.

I totally get what you mean, when i first came across them on ebay i was like damn.. that's pretty ugly.. but then when i saw what people had done with them

Weirdly when i was taking the fairings off i started to think... should i just restore it as is ?

[mark284811]

Speed addicted said:

I’ve got a (currently unwell) K100 that got cafed a few years ago, I’ll try to help when the electrical weirdness raises its head!
Have fun

Thanks. Considering i work in the semiconductor industry, I'm not looking forward to dealing with electrics. From what I've seen, if you want it to be semi-reliable and to modernise it, M Unit Blue seems to be the standard route.

[mark284811]

Marquezs Stabilisers said:

I want to see him go all in and build something like this

https://www.topspeed.com/motorcycles/motorcycle-ne...

That's hilarious... i wasn't expecting that when i clicked the link that's for sure.

[Speed addicted]

mark284811 said:

Speed addicted said:

I’ve got a (currently unwell) K100 that got cafed a few years ago, I’ll try to help when the electrical weirdness raises its head!
Have fun

Thanks. Considering i work in the semiconductor industry, I'm not looking forward to dealing with electrics. From what I've seen, if you want it to be semi-reliable and to modernise it, M Unit Blue seems to be the standard route.

Well, I found that if you want it to be reliable and don’t care about having a fuel gauge or pulling the clutch in to start then you don’t need one! Bloody m unit wasn’t about when I did mine, it would have simplified a lot.

They’re intolerant of imperfect earths, I ended up running an extra cable from the earth point under the tank straight to the battery, which solved some issues.

Looking at the pictures are you intending to cut the rear triangle out of the frame?
Again all this info wasn’t available when mine was done and I’d do things differently now. I get a seat unit/battery holder made that fits onto the triangle, now I’d cut out the whole thing and hide the battery somewhere else.

[mark284811]

Delivery Day

On the 20th of June 2022 as per the negotiations, the previous owner "dropped" the bike off at my house. I remember during the negotiations i needed to get him to deliver the bike for me as my other plans of getting it home had fallen through. He agreed to deliver it in his horse box which i thought would be fine. I did ask him though if there were anchor points in the horse box and he said he'd sort it out.

Upon arrival, he looked a little sheepish and then confessed that he heard a loud bang at one of the roundabouts. Upon opening the horse box door low and behold.... the bike was on its side. He was a little apologetic and said it didn't look "too" damaged other than the rear pannier that had smashed to pieces. I kept quiet to see how we were going to deal with this situation and he then opened the boot to reveal a bunch of maintenance spares and parts he's accumulated over the years along with two books "first being a Clymers manual and second being a trusty Haynes manual"

He explained that he was going to offer me the books and bits for a small amount of money, but considering the bike had fallen over he then just gave them to me which was good. I didn't have the heart to tell him that i didn't care about the damage, because everything that was damaged was likely going in the bin anyway.

So i put it in the garage, and then, later on, gave it an initial good going over with some degreasing spray/traffic film remover/pressure washer treatment. Trying to remove as much of the birds next/farmers' field out of the vents in the side of the fairing.

Next.. was to start the disassembly of the "easy bits" such as the fairing front and back

[mark284811]

Speed addicted said:

Well, I found that if you want it to be reliable and don’t care about having a fuel gauge or pulling the clutch in to start then you don’t need one! Bloody m unit wasn’t about when I did mine, it would have simplified a lot.

They’re intolerant of imperfect earths, I ended up running an extra cable from the earth point under the tank straight to the battery, which solved some issues.

Looking at the pictures are you intending to cut the rear triangle out of the frame?
Again all this info wasn’t available when mine was done and I’d do things differently now. I get a seat unit/battery holder made that fits onto the triangle, now I’d cut out the whole thing and hide the battery somewhere else.

Good to know about the earth situation. Yes, I'm more fortunate than your trail-blazing attempts

Oddly i kinda like the rear triangle section, i think I'll just remove the rest of the overhang from the rear end. I think the rear shock assembly and rear frame bit that people fabricate looks like "it's trying too hard" I'm also not fond of when people make the rear triangle "fully empty" yeah i don't want it cluttered like standard.. but i also think empty makes it look odd. So i hope i find some type of happy medium.

It's all down to peoples preference i guess and we're all different.

[Speed addicted]

This was mine in about 2014, before I spent far too much time relocating the battery and everything else to have an open frame under the seat.



This was in about 2018, moved battery, different headlight and bars etc.

It’s currently making worrying thunking sounds from deep in the engine, and is off the road. I’ll get back to it once I’ve finished renovating the house!
I’ve got three other bikes so it’s not really a priority just now.
Once I get back to it I’ll re-do the seat unit, and a load of other things that have annoyed me over the years.

One piece of advice I’d give anyone doing a project is to plan ahead!
I spent quite a lot of time (and money) because I was making it up as I went along and often had to change things I’d already done.
A more recent Ducati project was far more simple as I had a finished bike in mind!

Edited by Speed addicted on Friday 8th July 09:53

[mark284811]

Teardown Begins

So with the initial clean done, it was time to start stripping the easy-to-access and obvious stuff at the front end of the bike (Side fairings / Battery / Horns / Front fairings / Brackets that held all those bits on) and of course those damaged panniers.



Next day followed by (Seat / ECU / Rear fairing / Licence place holder / Mudguard)

Now was a good time to give it a bit more of a look over as well, tyres were over 10 years old, and the rear shock was perishing and that smell of petrol i could smell when i first looked at it confirmed that the tank was indeed leaking at the bottom middle on both sides where the seams of the tank meet.

My initial plan when i got it was to give it a full service, take it to an MOT station and "see what they found" before i stripped it. Obviously, the tyres and the shocks etc meant that wasn't going to be possible so instead of replacing the shock just for that benefit.. i decided to scrap that idea and just strip it entirely

[Drawweight]

All the hard work done already :-)

https://www.ebay.co.uk/itm/295078866837?hash=item4...

But probably not in the spirit of the thread

[mark284811]

Drawweight said:

All the hard work done already :-)

https://www.ebay.co.uk/itm/295078866837?hash=item4...

But probably not in the spirit of the thread

Not alot of information on why it’s a non runner that one. It’s not quite to my tastes either haha. But each to their own