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This story goes back in time to my youthful age of 18 when in 1982 I'd been into scooters for a couple years and had run LI150/GP125's. I'd got bored with standard output and began to tune them. The long road of tuning took place modifying cylinders, heads, upjetting and fitting larger carbs etc. Lots of modifications with very little output, it cost a lot but what the hell I had no ties at that time.
My first major step came when I bought a 200 Bare casing, cylinder and head. I then converted my Spanish 150 into the casing, I even used the old seals. It worked! A very potent engine indeed, but alas, 39 Borgos, 15 crankshafts, 1000 clutch plates later, well not quite but you get the picture not very reliable! Now being very naive I thought I could get a motorcycle cylinder assembly to fit and cure my problems. So off I trotted armed with not even a wooden ruler. Laugh! Laugh! they all did at bike shops, scrap yards and automotive engineers they all laughed.
Shame faced I bowed down and went off to do another little project. If I was eventually to do a motorcycle conversation I guess I needed to know about Liquid Cooling. Now those of you who may remember I rode a Liquid Cooled Lambretta called Waterfront Pacemaker from 1982-85. It was resprayed and rebuilt 3 times. It hardly missed a rally in those three years, I used it daily to work 20 miles a day, and took part in most L.C.G.B, events and the custom shows. At the time that bike was quite fast regularly reaching speeds of 85-90 mph, even P.C. Plod confirmed my speedo been correct at 85 mph but thats a different story.
When my L.C. finally gave up on me, as I travelled home from the 1985 Redcar rally, whilst changing into 4th at 70 mph my con rod snapped sending myself and passenger straight over my handle bars overtaking a Vespa whilst bouncing down the road! I'll never forget that kids face he was flat out then I over took him with my Lambretta following and then my passenger, so disgusted was he, he didnt even stop. So there we were walking round in circles on the central reservation of the A1 with my smashed up GP. I found myself working at Beedspeed at this time and into all kinds of new conversions, my scooters got left and certainly any motorcycle cylinder conversion didn't get thought of. I parted company with Beedspeed and found myself in a grubby little workshop trading as M.B. Developments. I'd spent six years developing my scooters and couldn't see anything changing so the name stuck Mark Broadhurst Developments. By this time its the mid 1980's and all wells in scootering no recession and things looked good for a young man just starting out in life. As I walked around my welders one day I found a Japanese cylinder barrel similar in size to a Lambretta, visions of horrendous speeds sat on a Lambretta came into my head and I just had to do it!
I purchased a second hand Yamaha 350 Liquid Cooled Power Valved cylinder and head. The Yamaha 350 YPVS was a very fast bike! it was a twin cylinder engine, both cylinders were separate but connected by a one piece cylinder head, each cylinder used a four petal reed assembly similar to a TS1. The thing about the 350 YPVS was it had a varying exhaust port called the power valve (to keep things simple) a electronically operated roller controlled the height of the exhaust port depending on engine revs, a small exhaust port at low revs targa exhaust port, at high revs. To make the cylinder work on a Lambretta engine I needed to make the power valve work and Lambretta electronics just wouldn't do. So my first hold up occurred I had to make a Japanese ignition work and off I went down that road of developments. Then alas the shit hit the fan, some Joker finally set fire to my business and in 30 minutes all was lost. Some parts did survive the fire - the Yamaha cylinder and head did, but not the power valve parts. A blessing in disguise it saved sometime. By now I'd moved my family and business back home to Doncaster and started from scratch working from a garden garage, with a little bit more time I started on the new cylinder.
What next? The cylinder was about the same length as a 200cc Lambretta but that was it! I wasn't happy with the design of the cylinder, for the job it was to do so I set about grinding and cutting away, out went the 4 petal block and in went a 6 petal. I modified the transfer passages so three fingers could quite easily go in aiming to get near motorcross/enduro style transfer shapes, the exhaust port had to be blocked up as the power valve parts went up in smoke so I ended up with a fixed exhaust port. All this sounds easy it wasn't! There were bits and pieces of Aluminium cut up, welded, reground, rewelded and on and on it went.
My business had started to get busy and I could only do my barrel in my spare time which there wasn't a lot of. We are up to around 1989/90 and I hadn't owned a 200 Lambretta since 1985, I wanted one so I kept at it.
The cylinder altered that much that not even Yamaha experts recognised 4. The head was a two in one so that needed parting off and welding up. After all this work it still had to fit onto a Lambretta engine casing and into a Lambretta frame not forgetting to allow for water pipes and switch units.
At this stage of the proceedings I had carried out numerous Japanese piston and rod conversions to TS1 motors this helped to set up the Yamaha engine. I chose to use a Yamaha IT175 piston and a con rod from a RD400 fitted to a GP200 crankshaft. Giving me a Bore of 66mm and stroke of 58mm giving 198cc the same as a Lambretta, which I considered its limit!
I had a new steel liner fitted and finally business pressures took over, I couldn't cope with the amount of work so after all that time the cylinder was put onto a shelf.
Until one day a customer called Richard, Ted, "take me away I'm insane", Milner approached me, he wanted something different to his stage 6 Suzuki with more speed and reliability, he didn't take too kindly to me offering large cc motorcyles, what could I do, then in a flash what the hell sell my cylinder and let someone else find my dreams.
I might have had a completed cylinder but no engine so a mass of ally welding took place to mate the base of the cylinder to the base of the casings. Back and forth from welders to machinists. I finally completed the engine and now I could start the frame.
My original thoughts was to cutout the frame section to allow the six petal reed assembly and carb to fit in the area of the tool box but that didn't work so a new manifold had to be manufactured and the carb came out thee same as with a TS1 kit. The frame still needed cutting and altering along with a weeks worth of work.
The fabrication of the frame included all the pipe work and bracketing for the Liquid Cooling, the radiator was sandwiched into a shaped horncasting the legshields and main frame section was cut to the spec required, the back end was made up to suit a small number plate and light, twin tanks were used, a dashboard was fitted to mount rev counter, temperature gauge, switch, light and expansion bottle. The forks were converted for Kawasaki dampers finally the standard stand was narrowed to suit the style of frame. All that lot was sprayed up in a Magenta and Blue metallic (Teds wishes) small parts were powder coated, polished and chrome plated.
By now I'd taken over a year from takin on the project and Ted was getting a bit impatient, I was basically rushed of my feet with all my normal work and for this reason don't take on bike rebuilds, well only the odd one to keep my finger in the pie and its the only side of my business that is still a hobby, I don't like to be rushed things can go wrong!
As it turned out after spending three days making a one off exhaust, of which Ted watched me and then realised just how long these things take the bike fired up! time and patience paid off, it all worked!
It was lust a case off nipping for a M.O.T. and road test. The cylinder porting didn't turn out as I wanted it, and it gave a weird and wonderful power band of which I wasn't used to. I hit a bump as it hit the power in third gear and pulled a great big wheeley my heart didn't slow down for another hour, well the bike seemed bloody quick!
The bike was soon collected and off Ted went, down the motorway off the clock! it seized! it had done less than 50 miles aren't you supposed to run them in? The piston freed and he carried on no problem.
The initial gearing was far too high, SX200 46 x 16. So I changed it to LI150 46 x 16. The bike was then much easier to ride, well within the speed limits. We were invited down to a rolling road test by the Scootering mag, the bike gave 115 mph and 23 bhp at the rear wheel, not the best managed but not bad for a road bike at the rear wheel.
To spread the power I modified the cylinder and head, to help the clutch I fitted a 6 plate conversion. The bike was then run at Avon park only to show I'd slowed it down. Well its still very fast, rideable and reliable which is what Ted wanted, its had a couple of teething problems nothing Ted couldn't do and now its done over 2000 miles its not needed a van so something must be right!
And so ends my dream from 10 years ago, would I do another well I learnt by my mistakes, I would go about it different next time! On to other things (I still haven't got a 200cc bike yet, I wonder what my 270cc engine will turn out to be).
SPEC. 66mm Bore x 58 Stroke. 198cc. Yamaha Piston, Yamaha con rod, Kawasaki 6 petal reeds, magnesium 34mm Dellorto, Motoplat 12v electronic, 6 plate clutch, LI150 gears 46 x 16 Tooth Sprockets, one off race exhaust, hydraulic front disc, Kawasaki dampers and much too more to mention, have a good look one day! Better still the machine is for sale at £2,200, as Ted needs finance for a trip to the Amazon rain forest,so ring me for details on 0709 - 869756.If its been sold I can probably still help you and i'm also an LCGB SUPERDEALER!!.