No, am not using the OEM service brake. I took your advice and installed the Polaris brake and disk. Using a Honda master cylinder for service brake and a Kawasaki master cylinder for emergancy brake. I think the problem I am having is not enough cable travel to actuate the service brake. If I use a hand lever to apply pressure to the master cylinder the brakes lock up. I may have to go to a foot brake for more leverage, even a extension I put on the finger lever was not sufficient to lock the wheels.
Here are a few pictures of the system which is still a work in progress. Also a picture of my Kart jack made from a rototiller base, works good. :-)
Enjoying the problems, they are making me think. :-)
RDomke@Comcast.Net