The spacer is fixated with two pieces of 8mm aluminium pipe, threaded with 6mm to screw them on the cylinder studs. These pipes protrude 7-8mm over the cylinder to center the head. Simple and effective!
Exhaust: 185-187
Main transfers: 123-125
Rear boost transfer: 118-120
Interval depending on squish clearance.
I'll measure the pipe later. It was cheap (€25, used) and it looks like an easy modification; Cut the 1st diffusor once, turn ~70-80 degrees, weld and re-weld. It is for the Piaggio Hi-Per2 engine = closest I could come to the 39,7-40mm (?) stroke of Top Racing crank. The conrod needs replacing but is fine for testing, but not for running 200km at full throttle after my DEAD KT60/SP60 hit reserve exiting a turn and hitting 13.000rpm = BOOM!
The piston dome is unfortunately concave, so a standard head must be modified to suit, rather than just skimming the head 0,xxmm. I'm therefore unsure which head I should use. The Minarelli's fins are positioned horizontically as opposed to the 45 degree angle of the Kreidler head. Less cooling arear as well... I'll just have the Kreidler head modified! Anything else seems wrong, now that I think about it.
Will fit the Vforce-reed cage as I already have a Rion setup on my 50cc engine. The big Stage6 inlet covers one of the mounting holes; I think fitting one plate with countersunk screw and soldering another plate to the inlet will do the trick!
The inlet is at an angle matching the original hex-nut-spacer-thing for the right engine cover perfectly for fitting an original inlet tube + Bing! An unmodified PHBG21 will need the front tube lengthened by 20-30mm to fit the 21mm Stage6 rubber inlet, though, but a 24-28mm carb should fit the Stage6 parts perfectly this way.
Or I can just fit a flat Polini-Malossi-whatever cage under the plate = easy, quick and 'good enough'. The less I think, the better my chances are at success!
18mm or 28mm carb won't matter, nor does maximum power at first. My primary goal is to see the effect of a modernised engine!
i.e. original looks but underneath better ports, reed valve, bigger bore and squishband! I am aware that it will likely run too hot with a normal 32mm exhaust, and I'm hoping an 80cc Kreidler exhaust on an expansion header will be 'ok'. Perfect, max power is secondary!
One thing I must add: The Stage6 reed valve from this kit has a rubber coating. Good for keeping it air tight! Problem is the rubber is dissolved by ethanol which by law is in all petrol. Never used the reeds - soaked it in petrol to clean it after I dropped it. Two days later the rubber started to buble and peel off... BAH!
Trash valve!