JJ Cobas K100R Flying Brick

[Ijustwanttoseethephotos]

But you haven't beadblasted all the bare aluminium casings!

 

[Motorcycle Michael]

Crankcases and sump blasted.
Bell housing will be black.
This is what happens when 3rd parties are involved. I was disappointed when I collected the engine because I'd asked for everything blasting.
No real drama though as it will tie in with the black 16valve gearbox and back end.
On the subject of the back end,I may try the Monolever rear due to weight. The Paralever set up is far heavier than the Mono-we'll see.
At the moment I'm still suffering from "bike builders remorse"!

 

[Ijustwanttoseethephotos]

I painted a customer's K1100 engine unit with Hammerite satin black without stripping the engine,(obviously the outer covers were removed and sprayed separately). The finished result was good but the preparation took hours, never again!
I'm building a K75 with a single carburettor conversion as a project for myself, that engine/gearbox has been beadblasted totally as everything was bare aluminium except the engine casings, there was a lot of dismantling and rebuilding to ensure the internals were kept bead free.
The K75 has the earlier Monolever rear swinging arm, with a drum rear brake, I much prefer the cleaner look of this set-up. I'd fit this to my 16V but unfortunately there's no wider wheel available than the 2.75". I think the narrower rear tyre would look odd with the front end.
I'm sure I've seen a drum-braked spoked rear wheel option, unfortunately the cost of getting both wheels converted would probably be more than the whole project!

 

[Motorcycle Michael]

I always use 2K satin. It never comes off and is OK with heat. It will go straight onto metal without primer but I always prime first.

I'm led to believe that late K75's were still Mono's but were fitted with K100 16 valve wheels-maybe worth looking into.

 

[Ijustwanttoseethephotos]

Unfortunately the only drum version I can find is the K75C, all 16V wheels are disc.

 

[Motorcycle Michael]

On the way now.
The engine and frame are now solid as I've made bushes to get rid of the rubber mounts on the 2 front engine fastening points. I'm not concerned if there are a few more vibrations and I'm hoping it might have made the chassis feel tighter. Some of the K1's didn't have the rubber mounts at the front.
Once it's on it's wheels I can start the exhaust exhaust headers. I've noticed tonight that there are no balance weights on the wheels and I'm pretty sure they haven't been done so it's back to the tyre shop for them.

 

[Ijustwanttoseethephotos]

My K100 16V engine is mounted without rubber mounts as standard, I've used A4 stainless steel fasteners which were close to their maximum recommended torque when the BMW torque setting for the engine bolts is applied. I check them regularly and there's been no problems.
With the standard cams it had a minor vibration patch at about 4500rpm, but that's disappeared with the replacement cams, definately nothing excessive.
You've got to machine all the Allen bolt heads to remove the manfacturer's markings! (Attention to detail!).
It's looking good!

 

[Motorcycle Michael]

You've got to machine all the Allen bolt heads to remove the manfacturer's markings! (Attention to detail!).
It's looking good!

This will be a "Go bike" not a "Show bike"!

 

[jonnie comet]

It's getting there.......Looking good Sir.......

 

[Motorcycle Michael]

The rear sets are 99% done. Just the gear lever position to get right.
I'm waiting for the modified water pump to arrive so I can fit the radiator,that should be here in the next few days.
I did have a glimmer of hope that I'd done the right thing in pursuing this project when I came by and bought a 1991 26000 mile K100RS 16v. I'd only ever ridden high mileage,well used K's before and to ride a perfectly preserved,taught K RS was like traveling back in time.
Everything worked as I would expect a 2 year old bike to function. Nice tight handling,reasonable,speed, suspension and adequate brakes. I've changed the brake pads so I'm hoping for an improvement there. I was particularly pleased with the handling!

It's given me the kick up my arse I needed to get stuck back in with vigor,it might be worth it after all!!

 

[timeandtide]

Just remember who recommended it!

 

[Motorcycle Michael]

Just remember who recommended it!

Thank you so much for the tip off. You were "On the case" there.
I'm not sure if you've seen it but I really think it's a keeper. There can't be many K100RS's around in this condition.
Steve hated it but weirdly,I love it- kinda reto cool?

Thanks again.

 

[timeandtide]

Thank you so much for the tip off. You were "On the case" there.
I'm not sure if you've seen it but I really think it's a keeper. There can't be many K100RS's around in this condition.
Steve hated it but weirdly,I love it- kinda reto cool?

Thanks again.

I had and was sorely tempted myself.
If I wasn't already the proud owner of "The Polished Turd" I would have indulged myself!

 

[comberjohn]

You mentioned wheels fitted to the K75, Michael.
They weren't the same as the 16v. They used them on the last of the 8v K100RS but were the same width as the older rims but with three spokes.
They were pretty and bolted straight in to the forks on earlier bikes but now they're just about impossible to find.
Have seen spoked wheels fitted to a K on another forum. Looked very nice.

 

[Motorcycle Michael]

You mentioned wheels fitted to the K75, Michael.
They weren't the same as the 16v. They used them on the last of the 8v K100RS but were the same width as the older rims but with three spokes.
They were pretty and bolted straight in to the forks on earlier bikes but now they're just about impossible to find.
Have seen spoked wheels fitted to a K on another forum. Looked very nice.

Hi John,thanks for the PM.
I'm sticking with stock 8 valve throttle bodies for the time being as a set of throttle bodies are currently under construction from billet.
They are based on older F1 tech and do not have butterflies!

 

[Ijustwanttoseethephotos]

Roller barrel throttle bodies?

 

[Motorcycle Michael]

That's right.

 

[Motorcycle Michael]

A little more.
I've just chipped a stock K100RS 16v and I'm amazed at the difference it's made.
I'll be installing a chip in the Brick's Motronic for sure.

Also,a shot of the top triple clamp and instruments.

 

[Ijustwanttoseethephotos]

The 8V electronics are totally different to the 16V, if you've had the 8V head reworked, you'll probably need an aftermarket ECU to enable you to re-map everything properly or you won't get the full benefit of the modifications.
The 8V ignition unit cannot be modified easily, if you've raised the compression ratio, you'll need to back the ignition off at certain rpm, you can't do that with the standard set-up.
I think BSK make a mappable system.

 

[Motorcycle Michael]

The 8V electronics are totally different to the 16V, if you've had the 8V head reworked, you'll probably need an aftermarket ECU to enable you to re-map everything properly or you won't get the full benefit of the modifications.
The 8V ignition unit cannot be modified easily, if you've raised the compression ratio, you'll need to back the ignition off at certain rpm, you can't do that with the standard set-up.
I think BSK make a mappable system.

I'm using 16 valve Motronic ignition because it gets rid of the car type air flow meter. It will also have 16v injectors because they have better atomisation properties.
I don't expect it to right from the start but the development's all part of the enjoyment.