Hi Rosco CT 125 uses 22 mm Kehin, SL 125 use 24 mm Kehin , 1977 XL 125 use 26mm oval type carby. Get rid of the CT head a use an XL head bigger valves std over the CT & SL heads. Easy to recognise XL head has the number 383 is stamped near the head gasket where CT has 384 . If ya can not find one I have a few of them. Used them in Bucket racing Dirt Track. Still got the bikes if any one wants to buy them. From memory your bike is locked in one gear . You can get them going with a bit of work 17 Hp out of mine.Valve train is the limiting factor use RD vavle springs with titanium retainers good for about 14,000rpm with the right cam grind. Are you allowed to use methanol.If you are going to rev it make sure the centrifugal filter on the end of the crank is a good one as they explode through the clutch side cover with a bang & destroys big bend immediatly.Been there done that a few times .
