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The Cheetah barrels as supplied neec some work. On the bottoms of the barrels there are fou' waterway □lunking plugs. The tapered threads ir the barrels are so poor sometimes :l blanking plugs stand proud and l cwe to be ground otf, sometimes they •tr* loose and need Aralditing in. s supplied the cylinder bores are too lu'fit and need specialist diamond 'fling to give at least 0.002in (0.06mm) iarance. All the cylinder-stud holes the barrels need helicoiling too ;ause the threads strip very easily.

The Americans run these engines on alcohol so the detachable cylinder-head domes they supply are far :oo high compression. Instead, I use 27cc domes to give a compression ratio of 7:1 from exhaust port closing.

On my outfit the carbs are 41mm PWK Keihin running with an electric pump from a CBR600 and the reed-blocks are from a Honda CR250 with V Force reed assemblies. For the ignition I have been using a self-generating PVL ignition with fixed ignition timing. And as with all my race bikes, Blue-Haze Engineering cid a lovely jcb with the exhausts (photo 4).

stop the crank being pushed from side to side. The oil-pump gear is helical and cannot be used with straight-cut gears, not that anyone should think of using an oil-pump with this set-up. Pre-mix of 150cc of Castrol 747 to every five Litres of Shell Optlmax Is the recipe I favour.

You can get sets of special clutch plates from the USA or use RD400 steel plates and XS250 fibre plates (they are wider with more friction area) and heavy-duty clutch springs. A needle-roller bearing fitted into the clutch pressure plate is a good idea too; it stops the clutch arm, rod and ball welding themselves together.

With my 535cc motor the primary trarsmission is more specialised (photo 3). The standard clutch housing would not fit over the larger RD500 clutch assembly whatever I tred, so I had to make a new one - not a simple job! There was no way of running a water pump so I bought an electric pump from Derion Tweaks. I removed the kick-start assembly and idler gear too because no way was I going to kick-start the beast.

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