CJS Customer Projects

999 Refining Stock Parts

A 999s test by optimising stock parts (no cams or expensive pistons added) of course it has a big fat exhaust pipe.

A chap from Sweden asked me to make some heads for use with his standard pistons.  I made the heads as usual and fitted some stainless 1 piece valves of stock size, new guides and flow benched the heads. The heads were milled and belt tension restored using oversize belt rollers bought from BCM Motorsports.  Cams were degreed to 110/110. The head flow and velocity after works was much improved. The fuel was corrected using a nemisis ecu mapped by www.biscaya.com

As you can see excellent power (151hp up from 135 or so) from flow/velocity and  the extra squish area that the milled heads provide. This works very well indeed with its stock flat topped pistons. The only problem with this conversion (if you’re the DIY type) is the cams must be degreed.  It's not a straight plug and play situation such as bolting on heads or throwing in some hi comps.  Hi comps alone may deliver around 4-5hp through the midrange but the top end is pretty much limited to around 140hp in both 998 and 999s engines.  Meaning the stage 1 port and skim or (stage 1 version 2) as I call it delivers bang for buck giving the same compression as hi-comps combined with better flow and a head being totally overhauled at the same time. The head includes colsibro valve guides, seat cutting ,tested  porting , polished and modified valves ,milled and modified combustion chambers and all for not much extra cost than buying a pair of hi comp pistons alone.

I have seen very few 999/998s bikes with expensive pistons and  being ported by big name firms barely giving anymore than 145hp.

What would you choose?

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