So fast forward a few years and what's happened? Well, Andy who owned the bike had thousands of trouble free miles with the kit and enjoyed it immensely, but times being hard n'all he had to part with the scooter. But the new owner (Alan) has run into a spot of bother.....he has holed a piston and written off the kit! Now I'm not exactly sure what's happened mechanically speaking since we last saw it, but when i stripped the engine for inspection, the ignition timing was 22+ BTDC, so I'm thinking there was an Adv/Ret box on....which has since been removed, but the timing not adjusted accordingly? But that's just a guess, as i say.....I've not seen the bike since we did the original test.
So, having received a new kit from Ron today, i was really pleased to see a few subtle, but very important updates. The head, and piston seem to have remained as they were, cowl cover is now black (which aesthetically i prefer) but the important changes are of course inside the cylinder:
1) Inlet port - timing duration remains the same, but the shape has changed. A much nicer 'softer' shape to the port, which will be kinder to the piston.
2) Transfer port timings look unchanged - same with the rear boost port but the casting looks cleaner inside and directional flow looks slightly better.
3) Exhaust port, this is the biggest change. It appears to be about 1.25mm higher thus giving increased timing duration, and 1mm wider each side, plus the shape/flow is much more angular and pronounced giving better blow-down area. This should bode well for performance, but as always.....the dyno will tell all.
Once we have rebuilt it and run it up, i'll follow up with some dyno graphs.
Old exhaust style:
New exhaust style:
Old inlet:
New inlet:
Kit:
Von Dutch:
