KR-1S.co.uk Forum

I find that a very weird place to put it ?

Seems an "easy to damage place" in case of a crash, while there is so much space in between the frame .
and you are doing lots of stuff to save weight, and then you are gonna add, by welding extra studs and use long cables.

Suzuki XRs, Yamaha YZRs and even Kawasaki's X-09 have their coils, powervalve control boxes etc in similar positions on the frame, Jan. This gives easy access to the parts. See this Suzuki RGV500 as an example:
http://www.mcnews.com.au/1998-suzuki-rg ... clid=IwAR2
The EXUP's steel mounting bracket is only used temporarily to accurately position the pillars and then discarded. If I had machined the pillars myself I'd have given them a bobbin shape to save weight, but even as pure cylinders they aren't all that heavy- the pair only weigh about 40 g.
Anyway, the point is NOT to crash, surely?

Hi Gerrit
When I saw the photo, I thought you were drilling through from the outside, but going to fit it on the inside.
I didn't realise that was the actual intended location for the servo.
I would have tried to mount it in the same location as the standard unit, just for simplicity.
Keep the photos coming

As previously said some great workmanship here..

I'm also interested in the position choice. Are you doing something interesting in the space of its original position?

I haven't finalised my ideas yet, Luders, but I do want to keep all options regarding the space between the frame spars open.
By the way, can anybody suggest a source for a replica 4TW1 (1996 TZ250) fairing?

That space is prime for doing something with the airbox. I can't remember where I got my fairing from.

The ZXR400L upper fork yoke requires a bush (18.1 mm ID, 25.1 mm OD, length 20 mm) to be fitted to the steering stem bore because of the smaller diameter of the KR-1S stem:



The bush OD and bore ID received a coating of green Loctite, after which the bush was pressed in place:



Test fitting of the steering stem, it fits!

Next: get a bush made to downsize the bore in the ZXR400L lower fork yoke to take the KR steering stem:

The KR-1(S) rear shock linkage knuckle:



Comparing the KR part with photos of the ZXR400 equivalent......





..... and the EX250 knuckle........



...... suggests the KR part is overengineered, so now to get a ZXR knuckle and compare the actual dimensions. I suspect some weight can be saved by trimming excess material from the KR knuckle. Photos of works Aprilia, Suzuki and Yamaha 250s in the Japanese "Racers" magazines indicate they have knuckles machined from solid, which all look lighter than the KR part.

Some EX models have a built-up knuckle:



Presumably this is a steel part. Interestingly, Kawasaki's last 250 racer, the ill-fated X-09, had a knuckle similarly built up of aluminium so making such a part might be an alternative, albeit an expensive one. Not sure whether there is enough room to accommodate such a built-up knuckle, though, so this has to be checked with a cardboard template first.

???

what is supposed to be over-engineerd about the KR knuckle ? it has a very basic shape with a lot of material left out where it is not needed.
And I doubt machining from solid will be lighter to. of course it can be lightened, but I wouldn't touch it (trim down), the weight gain will be minimal and you probably will weaken it.

It' s also one of the smallest knuckels in width, one from a ZXR needs much longer bolts.

That's why I want to compare the knuckles first, Jan. "Meten is weten", to measure is to know!

Today I received the machined parts for the replacement swingarm bearing sleeve; original steel KR-1S part at the top, needle bearing races and titanium sleeve below:



The needle bearing races are secured to the titanium spacer with green Loctite:



Weight of the original sleeve is 502 g, the replacement weighs 248 g. Should a bearing race become damaged a replacement is easily obtained as it's a standard SKF item; eventually the KR part will become "No Longer Available". Also, to reduce clearance between frame and sleeve the new setup is 0.5 mm longer than the standard KR sleeve's 213.5 mm.

Some previous idiot owner of my frame had cut off the front fairing stay lugs (don't ask me why!) and these have to be replaced. I had two lugs made, 200 length, 18mm OD, drilled 6 mm lengthwise:



Together with a set of late TZ250 brackets (Yamaha Part Nos. 4DP-2836A-00 and 4TW-2836E-00)......



.... and a length of 20 mm square aluminium tube, suitably drilled at one end......



.... result in a sturdy front fairing stay assembly:



Now to get the lugs welded to the frame, so it's off to the welder's.

Looks very good Gerrit