Author Topic: KX 85 and 100 cylinders, research for possible special  (Read 2805 times)

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Offline Phill Spowart

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KX 85 and 100 cylinders, research for possible special
« on: January 07, 2016, 01:06:07 AM »
Morning all,

I've got a few noob questions about KX 85 and 100 cylinders. I'm not a dirt bike rider, I do up classics (or obsolete old nails, if you prefer).

Last month someone posted on a kawasaki triples club facebook group an absolutely stunning special. A KH250 with three KX85 top ends grafted on. Article was all in japanese, but the pictures said plenty. I then had a look at what a KX is, and found that they were overbored to make the KX100... Using a stock KH crank (as the japanese chap apparently did), you'd get 340cc's.
So far I've found that you can rebore an 85 to 100, and overbore the 100 to about 54mm or so. Of course this would mean replating, but you'd get about 360ccs

So, my questions. Is there much difference between porting on the 85 and 100? The only 100 barrels I can find are in the US, if I could use 85s it'd be cheaper on postage. If there is a difference, for a road bike I'd prefer whichever has the calmer porting, which I'd guess would be the 100.

Are the overbore options worthwhile or do they tend to be unreliable?

Is there anyone who could get me some measurements from a 100 cylinder, or could I find a scrap 100 barrel and piston to prod and poke and see if it is feasible?