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K75 Madass Tue Nov 14, 2017 6:17 pm
Suzi Q
![Suzi Q](https://2img.net/u/4211/29/48/93/avatars/5422-6.jpg)
Life time member
![Life time member Life time member](https://i.servimg.com/u/f80/11/71/56/74/bmw-5s10.gif)
Well it wouldn't be my choice of a name, but it worked for Sachs...
Hi, I posted in the introductions section about a K75 project. Here's some more detail:
![K75 Madass Madass10](https://i.servimg.com/u/f62/19/80/79/25/madass10.jpg)
I came across two of these in a dealers a few years ago when a pal was having a tyre changed. I thought they looked great. Always had a mind to get one for fun. Thing is, they're not brilliant quality and they seem to be silly expensive for a pumped-up step-thru (it's a honda cub/C90 in beachwear).
Sooo, when I retired and needed a project (having rebuilt my K100 for the umpteenth time after yet another prang) I had a daft idea to see if I could make a Madass out of God's own motorbike - a 'K'...
Pretty soon it started to get Not Daft, there seemed to be a few serendipitous aspects to taking a K in this direction. Here's the sum total of the extensive computer modelling, ahem...
![K75 Madass K75_7511](https://i.servimg.com/u/f62/19/80/79/25/k75_7511.jpg)
Basically, when BMW conceived the K75 they left out the front cylinder and bent the front frame legs back (it says this in a book I've got!). I thought I'd shunt the K75 engine forward back up to the front wheel, because this would make room for the line of the frame/petrol tank as it skimmed the top of the bellhousing. Turns out this 'making room' would also even up the weight distribution (the finished bike is 103 kg front/102 kg rear), shorten the wheelbase (I moved the rear wheel forward by 25mm) and lengthen the K's swingarm (I decided on a highly-technical 50mm for the extension, because that was the size of ally billet I'd got to make a spacer - us shed-builders know how to deal with tricky decisions). I have a thing about the K's stubby swingarm anyway, all that jacking up of the back end can unload the rear wheel half way round a bend - if you're daft enough to overdo the rear preload and cane it with just 10mm of static sag...but that's another story (and rebuild, as it happened)
Never mind all this pseudo insight, the extra gap between the rear wheel and the swingarm front means I can have a Ducati style underseat exhaust! that's what really counts!
Now where's the hacksaw?
chris
Hi, I posted in the introductions section about a K75 project. Here's some more detail:
![K75 Madass Madass10](https://i.servimg.com/u/f62/19/80/79/25/madass10.jpg)
I came across two of these in a dealers a few years ago when a pal was having a tyre changed. I thought they looked great. Always had a mind to get one for fun. Thing is, they're not brilliant quality and they seem to be silly expensive for a pumped-up step-thru (it's a honda cub/C90 in beachwear).
Sooo, when I retired and needed a project (having rebuilt my K100 for the umpteenth time after yet another prang) I had a daft idea to see if I could make a Madass out of God's own motorbike - a 'K'...
Pretty soon it started to get Not Daft, there seemed to be a few serendipitous aspects to taking a K in this direction. Here's the sum total of the extensive computer modelling, ahem...
![K75 Madass K75_7511](https://i.servimg.com/u/f62/19/80/79/25/k75_7511.jpg)
Basically, when BMW conceived the K75 they left out the front cylinder and bent the front frame legs back (it says this in a book I've got!). I thought I'd shunt the K75 engine forward back up to the front wheel, because this would make room for the line of the frame/petrol tank as it skimmed the top of the bellhousing. Turns out this 'making room' would also even up the weight distribution (the finished bike is 103 kg front/102 kg rear), shorten the wheelbase (I moved the rear wheel forward by 25mm) and lengthen the K's swingarm (I decided on a highly-technical 50mm for the extension, because that was the size of ally billet I'd got to make a spacer - us shed-builders know how to deal with tricky decisions). I have a thing about the K's stubby swingarm anyway, all that jacking up of the back end can unload the rear wheel half way round a bend - if you're daft enough to overdo the rear preload and cane it with just 10mm of static sag...but that's another story (and rebuild, as it happened)
Never mind all this pseudo insight, the extra gap between the rear wheel and the swingarm front means I can have a Ducati style underseat exhaust! that's what really counts!
Now where's the hacksaw?
chris
Last edited by chris846 on Wed Nov 15, 2017 3:46 pm; edited 1 time in total (Reason for editing : it was wrong...)