KR-1S.co.uk Forum

Broken one of the disc valves on your KR ? You'll struggle to damage the metal bit, but the nylon inner can strip its teeth or become detached altogether. New parts are no longer available.



The AR125 shares a similar design of engine and parts for those are much easier to find. The disc valve is a different part though.

However, I've been handed top secret technical information from Kawasaki in Japan that suggests the AR part can be used in the KR engine. I don't have any details other than that shown in the memo's, which I've scanned below (click 'em for bigger versions). And if anyone tries it or has any other advice to offer, please let me know.

Just had a quick read not sure if this info will help or not but when i rebuilt my engine i hit the disc valves with a die grinder and and took some of the opening and closing edges to increase the "timing" which made a differance to the engines behaviour in a good way !!

So taking that into account evan if they dont line up spot on it would be a good opertunity to do a bit of modding to the disc valves and increase their timing !!

RAVEN wrote:Just had a quick read not sure if this info will help or not but when i rebuilt my engine i hit the disc valves with a die grinder and and took some of the opening and closing edges to increase the "timing" which made a differance to the engines behaviour in a good way !!

I've often wondered about doing that, but wouldn't have a clue how much to remove from which edge.
How much did you remove, and how did it change the engines characteristics?

Ok from memory ( take into account this happened over 10 years ago ) i think i made the opening 8 - 10 degrees earlier and the closeing 5 degrees later .
Now i am not 100% on the opening but am 99% on the closeing , you need to keep the same profile/shape of the disc when you grind off the extra metal .

I used a protractor with an arm that swung out from the centre to work it out then just gently grind off the extra , dont go hell for leather with a die grinder you dont want lots of heat to get into the disc's .

As for what it did to the engine it made her snappier and more willing up top but i remember loosing some bottom end from the rev range ( who cares about bottom end revs right its a 2 stroke ! ) .
I did also change the reed valves but dont ask where or what from that part of my brains memory has been erased but drinking games gone to far !

I hope that helps some

RAVEN wrote: I did also change the reed valves but dont ask where or what from that part of my brains memory has been erased but drinking games gone to far !

fair comment raven