EK001 KSS/KTS ENGINE

I have a MKII KSS engine in a spring frame and I am looking to increase its capacity to near 500cc. Has anyone any experience or knowledge how to do this? - Dai Gibbison 16/3/2001

My advice would be not to do it .I have and I believe more could have been acheived by one of the after market go fast heads and cam.I can elaborate but you start by boreing out cases for the larger barrel Then the head to the barrel, which should be changed because now you need more gas for the size of the bore. I changed cams to Venom but you may want to get real racey.Now your Verticle Shaft and Rods need to be lengthend .Of course your carberatur needs attension .Larger or at least jetted.New Pipe of course.I will stop fo now.I would advise to buy an MSS if you need more inches. But you know what they say ITS NOT THE SIZE BUT HOW YOU USE IT.--CLAY BURTON 29/3/2001

Clay thank you for you response you talk a lot of sense – but so did my mother when she warned me not to ride motorbikes!!!
See - I’ve got this spare pair of crankcases, a head that has been bored out to 1 3/32 inch and a 10TT9 to match. My spare barrel is already + 60, I like a challenge and being different.
As for size, well I could have gone for a bigger Triumph vibrator, however -
“…. YOU JUST CAN’T COMPETE, WITH THE SLOW AND STEADY BEAT OF A VELOCETTE ON FULL BORE.” - Dai Gibbison 2/5/2001

I believe this can be done to about 410 or 420 cc by boring out and fitting a piston from a BSA B40 . This used to be one of the dodges by the racing fraternity to give a bit more go ( but kept quiet about I guess ) . In the late 80's I had a KSS racer that I used in VOC and VMCC events that had this 'mod ' on the engine ( among many others ) prior to my getting the bike .
I don't know the technical details, but it may prompt some discussion Your other correspondent is right in saying that there is much additional work to do porting the head and changing the carb to get the full benefit. - Alan Lawrence 18/5/2002