K100 race bike

[gavthirtyseven]

Hi all, new here on Motobrick, and new to BMW ownership as well. In fact so new all I currently own is a rear wheel!

I'm about to get underway on a k100 race bike project for BEARS (Brit, Euro, American, Race Series) racing in New Zealand. I'm aiming to start with a 16v paralever rear end k100rs, mainly due to the inreased power over the 8v model.

Parts collecting has started with a 17 x 5 inch rearwheel from a late model R series, and I think a RAM rear shock will soon be making its way to me, and some stiffer fork springs.

I suppose I'll have a few thousand issues to solve along the way, but the plan is to leave the motor pretty standard and remove as much as possible from the bike and fit some clip on bars, rear sets, modern race tyres (hence the new wheel!), and fibreglass single seat unit.

As part of this process I'll junk the standard clocks and replace with single tacho and engine temp sensor.

Has anyone any idea on what tacho I could fit from any other bike? I guess the K100 has an electronic sensor as opposed to a cable/gear arrangement from the gearbox?
Not looking to break the bank on this project so a tacho from another bike off ebay should be cheaper than a specific race unit from Koso, vapor, etc. And I can get searching on ebay now for one.

Do the later K100rs bikes have a temp guage (water) or just a warning light? What temp does that light kick in at?
Any other ideas, hints and tips welcome.
Just need to get a bike now :embarass:

Thanks BMW dudes!

[tsunamiblack]

Hello, sounds a great idea! Have you had a look at www.oldracer.co.uk, they've competed a k100 at the B.E.A.R.S series. I don't know if its of any use but I used a www.trailtech.net speedo for my offroad bike and it was very easy to fit and didn't rely on any standard pre-installed pickups. The website has all the user manuals etc. Make sure you keep us updated!

Good luck

[Rick G]

You may get some interesting info here www.bskspeedworks.co.uk

[gavthirtyseven]

Yes that BSK speedworks / old racer bike is really the inspiration for my build. Cool bike :drool:
I like the air intake idea next to the radiator...might have to do the same. cool shades
The standard 16v k100rs quoted power and torque figures should make a good race bike if enough weight can be removed and the handling/tyres improved... well if not it'll look pretty :lol:
I'm hoping to avoid the costs of cams and complete new ecu and wiring of the BSK bike.
I also have a great write up in an old Classic racer magazine of the jj Cobas K-brick bike as well for even more inspiration... :2thumbup:

As for the trail tech unit - Yes I've seen a few other units like that but was hoping to get a real 'moving needle' display for the tacho as they are a bit clearer to see when racing.

Thanks for the input so far...

 
 

[Rick G]

I scored a set of 1200 cams and want to try them in the K1100. I am not even sure they are different but I got them for nothin so worth a go and the other thing is some port work and 1200 throttle bodies to make them breath then this and then that then more of it and on it goes. I seem to remember doing that to a Z900 till I ended up with a blown alcohol bike running mid 8s in 1980.  Thats probably why I havent got any money now, but it was fun.

[gavthirtyseven]

Yes, I'd like to keep away from the engine as much as possible, just removing stuff not adding - yet! :hmm:

[gavthirtyseven]

A few more weeks have passed, and the parts collecting is coming on well...
As well as the 17 x 5 wheel, Ive added:-
Race sigle seat unit (Z-But !?) looked cool on ebay, and very similar to the Old Bike Bears bike, and a small nose cone usually used on a honda hornet race bike,
Tomaselli quick action throttle,
SV650 clip ons, with 0.7mm removed on the lathe should be a perfect fit
2 new(ish) front discs
and finally - most importantly - a bike! Yay! a 91 k100rs 16v. Yipee! :lol:
Was looking all over NZ and France and the UK for a suitable (err - cheap!) scruffy bike to turn into a race bike and one shows up in NZ only 5km from where I live :2thumbup: Except I'm in France at the moment til January working :hmm: :confused:
Thankfully a friend has been and checked it out, talked him down a few $$ and it now sits in his garage :yes

Just in the process of getting a shock sorted and wondered if anyone here has fitted a longer that standard (380mm) shock to the rear of the Paralever equiped bikes? K1, 100, 1100?
Can either get a Progressive suspension built up with a ride height adjuster, or a RAM suspension unit with a standard, plus a 15mm longer top mounting... Still pondering... :hmm:

Anyway, we're getting there, and I need to remember that old Russian saying about slowing down "Remember 9 pregnant ladies do not make a baby in 1 month!" :loco:

[OldRacer]

Good luck and keep in touch, i may be able to save you a few hundred hours/$ of trial and error...

Ben,


www.bskspeedworks.co.uk
www.oldracer.co.uk

[gavthirtyseven]

Just another quick update...
Shock and forksprings ordered, definately recommend RAM suspension. Google RAM suspension.
Super helpful with advice and very fast turn around. Also if your out side the UK they are able to knock off the VAT tax (20% !!!) so worked well for me, an expat kiwi working in France!

Thanks as well 'old racer' Ben, for your email a while back. Would have got the suspension from you, but decided to go direct to RAM as I was after some shock length adjustment. Will certainly keep in touch though as the build progresses. Good write up in the new 'Classic Racer' mag by the way - plus a few other action pics scattered about the magazine :2thumbup:
Just a couple of quick questions; Ben, when you ran the K100rs / K1100 forks with the RAM springs, what oil weight and level did you run? 

Anyone else, have any of you tried replacing the std coils with stick coils as fitted to newer sports bikes?

Thanks for the help so far guys. I'll be back in NZ with my pile of ebay bits for my bike soon... :lol:

[OldRacer]

Hi, glad to hear its going well. Lets see some pics when you get a chance. I used 15wt oil with 450cc in each leg, dropped the yokes 18mm. They worked very well on the track, until they banned them (the cut off date is 1985 for BEARS UK) and i had to fit K100 forks, which need more like 30wt oil!
A few of the other guys using K100 forks have maxton or racetec internals but you can kiss goodbye to £600.

[gavthirtyseven]

OK,
all the goodies are on the way to NZ in a big wooden box, the bike is waiting for me in a friends garage, also on the other side of the world.
I'm sort of in limbo now, not much to do but think about the project and study the over-complicated wiring diagrams for what and how to remove...
Anyway here's the starting point, (not sure if its a he or a she yet!)

[gavthirtyseven]

Right then....
Back in nz, back to work sadly, and trying to find time to get the project started!
Finally picked up the bike and got to stripping down the outer layers to see what lies beneath ...
Initial impressions weren't to good, with a little more damage and decay than I was first expecting, luckily it seems to be limited to cosmetic stuff and most of the obvious signs of a clocked high mileage bike are missing. The foot peg rubbers, handgrips, frame paint, and seat all seem to back up the indicated 25,000 or so km on the odo. So happy there.
Sadly the brakes are non existent after sitting a while I guess the calipers are seized up solid so a big clean and strip job there...
Good to be back into it though and I'll try to keep this thread up to date as the build progresses.
But for now here's some pics after the first hour...

[frogy]

Nice project...mine is not aimed at the track,but for a stripped-naked look.I will also want to remove the airbox to see more engine.Thanks to Duck I now have the adapter to do that.But I will 1st get the bike back on the road with orig. airbox to get a baseline to see if I lose any power thru diff.rpms when I go boxless :lol:

[Jeff Sichoe]

Hey dude! I'm in NZ too and very interested in this build, keep up the good work :)

[gavthirtyseven]

Well the weekends here and I'll hopefully get a few more hours on the project... Hopefully! Good to see another kiwi on here. These k bikes have been raced here in nz before and a mate is trying to hook me up with some pics and details. Also I think I saw a photo of one at the gisbourne beach races a few years ago...
Anyhow, don't for get to let us know how that air box removal mod works out. I'm keen for any weight loss and power increase. Might be some issues with air flow sensor though...?
Right roll on the weekend!

[frogy]

By "issues" of airflow sensor,if you mean fitting a round hose to the square plate on the sensor Duck helped me out on that problem with an adapter that he had laying around.
Ive always wondered if Duck has enough pieces laying around to build another K :giggles

[frankenduck]

Ive always wondered if Duck has enough pieces laying around to build another K :giggles

Of course I do and there's another one in the pipeline. My spring project should  be completed in a month or two and I'll post some pics when it's finished.

[frogy]

 :lol: :giggles :hehehe

[gavthirtyseven]

Man, I feel like a fraud. No sooner had I posted up about getting a good lot of work done than both children and then my partner go down with a stomach bug and I didn't even get into the garage at all! Maybe next weekend ....
Be keen to find out the difference in air box vs no air box power wise . And then some more info on the round to square adapter thingy.??

[frankenduck]

Be keen to find out the difference in air box vs no air box power wise.

Answer: Zero.  Same result if you run the bike with no air filter at all.

[frogy]

Hey there Duck, I was not expecting an improvement due to air volume of factory air filter. My worry was that I would be restricting , or changing for the worse the air flow,thereby changing my torque curve.
When you had on your bike did you notice any downsides to the K&N set up,other than filter getting dirty faster ?
I would really like to yank that box out of the bike while I have it apart in the garage now vs during riding season.

[frankenduck]

1 - From what I understand the OEM filter does a better job and the K&N lets more crud through.

2 - Next, given how hot the engine compartment gets on K bikes, the oil in the K&N is probably going to dry out faster than it does on other vehicles so you'd probably want to service it more often than their recommended interval.

3 - Engines perform better with cooler intake air. The OEM setup pulls air from the front.  If you replace the OEM box with a cone then you're going to be pulling in warmer air from the engine compartment, especially on a faired bike.

Those are the reasons I choose to just run my bikes with the OEM filter box setup.

[Inge K.]

+1..........and usually some of the oil at the KN filters is drawn into the TB's, and collecting the crud which the KN's let through.

Inge K.

[Qdude]

 :2thumbup:

[frankenduck]

My worry was that I would be restricting , or changing for the worse the air flow,thereby changing my torque curve.

I think the biggest air restriction is the is the intake port on the mass airflow sensor.