The run up to, and the 1979 season itself was actually a very interesting period in terms of development. During the coarse of 1978 Chris came up with an idea for producing a 225 with four transfer ports plus a boost port. Bear in mind this was well before the times of buying such items off the shelf; and where it would be relatively easy to produce a 150 or perhaps even a 200 with multiple transfer ports, the walls of a Lambretta barrel (which is all that was available) when bored out to 70mm were quite thin leaving no 'depth' for extra transfer ports.However Chris had ideas to overcome this, the plan was to move out the two top barrel studs on the inlet side, so new stud holes were drilled down through the barrel fins. A plate 8.5mm thick was to go under the barrel, so both barrel and crankcase had to be machined to accommodate this. The plate merely had holes in the usual four barrel stud positions, the two exhaust side studs simply passed through the plate and secured into the crankcase in the usual way. Two allen bolts then secured the plate to the normal inlet side stud fixings in the crankcase. Two additional threaded holes were located in the plate to line up with the new 'outboard' stud holes drilled down through the barrel. A new much larger and beefier cylinder head was manufactured from scratch with holes to line up with the new outboard barrel studs.The barrel wall was made thicker using Devcon to allow for the extra transfer and boost ports to be ground into the barrel wall. A Powermax piston as in the two previous years was again used. Total open period for the ports were Exhaust 170o, Inlet 186o, and Transfers 120o. Once again the Mk II 34mm Amal and large bore scooter exhaust were used. Cosmetically, a new paint job, now all red.
Here's a few images, first is the finished article ready for the 1979 season.Second image , strip down and preparation in the back garden between meetings; and in case you hadn't noticed red is the favourite colour.Third, its the Hampshire Union Mob again, from left: Graham Oliver, Geoff Stephens, Steve Collett and Dave Hayward. Once again moustaches are compulsory.
The question is I guess, how did it go? Well at Snetterton the first meeting of the season I only managed e few laps of practice. It certainly felt quick and had real punch, however it seized very easily and so I never made it to the races. Although the engine showed great potential I didn't want to be traveling all the way to meetings only to seize or break down after a few laps and so I returned to using last years engine. The plan being to sort out the seizure problem and then get it back on the track.It seems a terrible waste but after all the work that was put into this multi port barrel it did not get the continuing development it really deserved. That said it was given another chance in 1983; the barrel was rebored to give slightly more clearance and a Yamaha piston used this time plus some of the Devcon filling was removed around the outside of the barrel to help improve cooling.First outing this time was at Three Sisters. I was being rather cautious with the jetting and tentative with the throttle but by the second race I was gaining in confidence, the engine now running sweetly and I managed to get into 2nd place behind Mick Hayman. The engine did feel good and as stated before was really punchy, I remember coming up behind Bob West during the second race and just squirting by on one of the very short straight sections at this circuit; testament to the mid range punch the engine possessed as Bob West was no slouch. So having got into 2nd place with Mick Hayman in my sights the motor just cut, which embarrassingly for an Electrician turned out to be a faulty ignition switch. Still, best showing so far. Next meeting was Lydden in May where it suffered the dreaded seizure while lying second in the first race and I only managed a 4th place in the second race. Final outing for the multi port 225 was again at Lydden this time in June. See - Racing 70’s & 80’s 1980 to 1983 for the story of what happened on the day. In the last image on that page if you follow the link you can see the plate previously mentioned that was used to out-space the top barrel studs to make space for the extra transfer ports.Returning to 1979, in addition to the original development of the multi port 225 Chris suggested developing a Disc Valve induction Lambretta. Disc valves were in common use on all the racing bikes of the time, before everyone went over to Reed induction.This was to be development on a shoestring budget as you will see from the specification and so it was decided the Disc Valve would be fitted to a 150 special. A standard 150 barrel and piston were used from spares lying around; the transfer timing was standard at 120o , the exhaust was advanced to a meager 163o. A boost port was also ground into the barrel on the inlet side and the inlet port was filled with Devcon; this was topped with a standard side squish head machined down by 1.5mm.The mag flange of coarse formed the housing for the Disc Valve with the internal recesses also filled with Devcon. An outer housing was machined to enclose the disc valve and to mount the carburettor and points for the ignition. One of the benefits of using a Disc Valve of coarse is the ability to use asymmetrical port timings, so taking full advantage of this the inlet port timings were arranged thus, open 41o A.B.D.C and close 65o A.T.D.C giving total open period of 204o.A 30mm Dellorto carburettor was used and an expansion chamber from a Yamaha Kart was utilised for the exhaust, which of coarse had been designed for a much higher revving engine than this was going to be, but it was available and as I said this was development on a shoestring budget.An air scoop was formed out of some sheet steel for cooling as of coarse there was no flywheel to provide this. A cut down frame was cobbled together with rear set footrests and clip on bars but no legshields, a full dual Ancillotti seat and the one element of luxury, a hydraulic front disc brake; which probably meant the bike was going to decelerate much quicker than it would accelerate!This was after all a test bed for a Disc Valve conversion which we had no idea how effective or successful that might be. Must be time for an image. Unbelievably I do not have any images of the Disc Valve itself, nor any close up views of it on the bike, which if you feel disappointed about let me tell you I am mortified I did not have the presence of mind to take a few photo's. I'll go stand in the corner with the pointed hat on.However there are a couple of general images, first is of the bike on the trailer along with Steve Collett's 150 Standard, with myself and Steve also in the picture.The second was taken during a race at Lydden.
Ok, so it's that question again, how did it go? First meeting attended with the Disc Valve 150 Special was at Clay Pigeon, which couldn't have been better really because it was a very tight twisty circuit with no long straights. Given the current state of tune, the bike was not going to reach a particularly high top speed but was likely to deliver more at the low and mid range, so this circuit would be it's best chance of mixing it with the other guys in the class.I had also entered the Newcomers to acclimatise myself with the bike as I had not ridden it before, only started it down the road outside the house, and I needed to get used to riding in what was a completely different position to my Group 6 bike. So after starting the bike, making some minor mods to the carburation it was out onto the track for practice and the Newcomer sessions. Everything just seemed to fall into place, the engine was running beautifully, I loved the riding position, it was clearly rev limited by the meager exhaust timing but as anticipated, delivered in the low and mid range.Onto the first race, I can still vividly remember sitting on the start line waiting for the flag to drop and then pulling a huge wheelie when it did, anyway by the end of the first lap I was in third place behind Tony Pawsey with Dave Webster leading on his 'state of the art' 150 Special. Tony and I had a great battle throughout the entire race but I did manage to slip by on lap 11 of 13 when he out-braked himself going into the hairpin and so I finished 2nd.Well an entirely unexpected result in the first race meant that I was very eagerly awaiting the second race, which got off to a better start, no wheelie this time and in fact I led the race for 3 laps until rather inevitably being passed by Dave Webster. However I maintained this position throughout the race and so once again finished 2nd. All the credit for this bike has to go to Chris, it was a fantastic innovation in terms of designing and building a Disc Valve for a Lambretta, it was equally remarkable the level of performance achieved with a collection of second hand bits and pieces, not to mention the low level of tuning applied to the barrel.In common with the multi port 225 the Disc Valve 150 never really got the development that it should have, which is almost criminal, however I rode it at two other meetings in 1979, Darley Moor where I finished 5th and 3rd and at Lydden a 4th and NS.That sadly was as far as the Disc Valve 150 went but I have to say that it was immensely satisfying and enjoyable while it lasted.