Since 1975 I had been using a Les Rafferty tuned 225 and I could not have asked for more as it had afforded me success in Group 6 and proved to be very reliable and had never seized in the two seasons that I raced with it; which many 225 engines were notorious for.The only fly in the ointment were the pistons which struggled with the extra stress of being in a racing engine and so with a desire to switch to a more robust, reliable piston and of course the never ending search for more power some changes had to be made.I was not fortunate enough to know Les Rafferty on a really personal level and had acquired the current 225 barrel through Geoff Stephens, so I was not really in a position to make any requests from Les for an alternative barrel/piston. In addition to the fact that I believe due to increasing business commitments Les had less time to spend producing new barrels for racing. So it was rather fortunate that Chris Harley who had introduced me to racing and who was in fact an undergraduate mechanical engineer at this time had some ideas about making the necessary changes for the coming season. Chris's talent for engineering was to prove very useful over the coming years because although I did all my own 'spanner' work it was Chris who was the brains behind the tuning of my bike up until I retired from the sport in 1983.Back to preparation for this year, the plan was to use a Hepolite Powermax piston from the 250 Greeves Griffon scrambler which had a 70mm bore so perfect for a 225. Due to differences in length of piston and relative position of gudgeon pin 5mm was machined off the bottom of the barrel and 1mm off the top. This gave 130o timing for the transfers 10o more than had been used previously. The inlet and exhaust were both at 170o and this was 10o less than used previously. Cylinder head was machined to suit the now flat top piston being used. A 34mm Mk II Amal Carb was fitted, quite a big step up from the 30mm Dellorto previously used, the exhaust was still a large bore 'gutted' scooter system. A special flywheel was made using just the centre boss from an original flywheel with a machined aluminium spacer to attach a plastic fan from a Heinkel engine; total weight, just under 1Lb.Last of all, cosmetic changes, ditched the LD tank and fitted standard, also fitted plastic GP toolbox to house battery and fitted GP headset, had the paint brush out again, now it's black & white. Here's a couple of pictures.
Well I couldn't have asked for a much better start to the season, the first meeting being at Snetterton in March. I had run the engine in on the road but also decided to go out with the Newcomers for a few extra miles for running in and getting the setup just right.In the first race I had a close battle with Ray Kemp but eventually took the flag, however honours were reversed in the second race and Ray came out on top. Very rewarding given all the work and changes that had been made to the bike.It wasn't only a good day for me as Geoff Stephens finished overall 1st in Group 3 & 4, Steve Collett overall 2nd in Group 3, Graham Oliver overall 1st in Group 5 and Alan Crickmore & Pete Hinsley overall 1st in Group 7. A great start to the season for Hampshire Union!A few images from the 1977 season; first one is at the hairpin at Cadwell in April where I am just in front of Pete Mullinder. Second image is again Cadwell this time in June, third image is at Darley Moor in August and the fourth is the hairpin at Lydden during the Festival of Speed in May. This was the first meeting I had used the hydraulic disc brake conversion, which very quickly caught on and was originally introduced I believe by Mick Hayman.
Over the course of the season the engine was tweaked to try and improve the performance even further. Although performance was very good it was quite noticeable how the power dropped off at higher revs in top gear especially up hill or against a strong wind. This was improved by machining 1mm off the bottom of the barrel to retard the transfer timing a little which brought it down to 126o from 130o. The Inlet and Exhaust port timings were also advanced slightly from original setup during the season.1977 continued to be a good year and in fact turned out to be my best season overall. It was another good season for Hampshire Union as well with Geoff Stephens finishing top of Group 3 and 4th overall solo, Steve Collett finished 3rd in Group 3 and 10th overall solo, Graham Oliver won Group 5 and finished 3rd overall solo, I finished top of group 6 and 2nd overall solo.Plans were already in place for further modifications to the engine for next year.