For those that are building a 270°/277° phased XS650 motor and are waiting for an ignition system, the Newtronics is available and it works.

The first prototype has been delivered and fitted to a 270° motor, which also included a Wiseco 81mm piston kit, a Frank Trost No.1 grind cam, 38mm carbs and a free flow exhaust system, this particular motor is fitted into a '81 Special with side car. For a reasonable comparison this motor has replaced a 750-kitted motor, the same carbs, cylinder head and exhaust have been used. This motor also ran a standard Newtronics ignition system. 

The ignition kit comprises of fully adjustable backing plate suitable for standard, 270° and 277° motors, two photoelectric cells a chopper plate, black box and wiring harness.

To fit this ignition system the points housing has to be modified for clearance, this involves deepening the housing by 1.5mm as illustrated by the picture above right, also the 2 bottom countersunk mounting holes also have to be deepened to clear the plates on the underside of the board, which retain the sensors. Full instructions will be supplied with the kit from Newtronics. 

The timing was set at 10° initial; a full advance was reduced to 34° at 3500RPM with this setting we found excellent power throughout the rev range and no detonation despite the compression ratio being over 10:1 vibration pattern has altered substantially, now rear view mirror vision is very clear at 100KPH / 62MPH where as before these mirrors were useless at anything over 60KPH . 
As soon as practical we will be conducting further tests on a motor cycle dyno, there will also be a comparison done between this motor, a stock 650 & a 750- kitted/standard crank motor. 

FIRST RIDING IMPRESSIONS

The first thing that can be noticed when the engine is idling is the slightly different exhaust beat, rev the engine to 3000 / 3500RPM and the amount of reduction in engine vibration is apparent, this particular motor with its "sport grind" camshaft was not built for low end torque but was relying on pure cubic inches to replace any low rev lost power and torque. This theory has worked and the motor pulls cleanly from under 2000RPM with someone in the side car, the big benefits with this entire set up is the top end power that is available (running standard 17/34 gearing) highway cruising and hills are taken with ease and at this stage 140KPH has been reached with hardly more than half throttle, engine vibration as explained earlier is greatly reduced, although at 6000RPM in 5th, there is a mild vibration but still not enough to upset rear-vision. Overall the modification has transformed the bike, although the starter motor struggles to overcome the high compression, it starts very easily. 
The only thing that has been noticed with this conversion is the amount of drive chain snatch when pulling from low revs, but this may be due to the fact that I have lengthened the swing arm by one and a half inches, although this was not a problem with the 360° crank, I can only think that maybe the closer firing pulses may have some thing to do with it, this problem may be unique to my application and is of no immediate concern. As was also mentioned earlier with the mechanical advance unit timing can be adjusted to any engine modification, the adjustments that we made to mine despite the actual 10.25:1 compression ratio does not exhibit any detonation problems whatsoever. Well how does it actually compare to the 750 that was in the outfit to begin with, well the original did not try to lift the front wheel when accelerating in first gear, this is rather scary in an outfit as the bike wants to turn left, rapidly. To conduct the dyno testing the sidecar will be removed, I think I am going to have some fun!!

Dave Bath with his 750cc 270° '81 Special and sidecar.