100 mph on a VL -concluded
From Steve Slocombe

2003 update This year I heard about an annual run on an airfield that allowed both quarter mile sprinting and maximum speed attempts. I fitted the lightened 4.25 inch stroke flywheel assembly - dynamically balanced with a 46% balance factor - which brought the swept volume up to 1358 cc /82.8 cubic inches and the compression ratio on my nearly stock iron heads up to about 5.6 to 1. I had read that gas flow was more important than compression ratio on the flatheads, and also that the old Muroc Lake speed runs were performed in one direction only, and probably with a following wind. So as long as I stayed street legal, I was comfortable stretching the definition of ‘stock’. I fitted the titanium valves I had had made in California the previous winter, which are 50 grams each lighter than the stainless ones I’d been running. The repro valve lifters are also 10 grams each lighter than originals, so that made 250 grams/half a pound less reciprocating weight. The thinned left hand flywheel saved about 1.5 kg/3 lbs, and removing the safety guard and replacing the mechanical klaxon with a battery bicycle horn saved another 4 kg/9 lbs. It was a shame my leather suit seemed to have shrunk over the holiday season, so perhaps the bike plus rider weight was not reduced that much. This time I had to fit a rear chain guard and a handlebar mounted kill button to meet the race regulations, and also carry a dog tag with my name, date of birth and blood group - this was serious!

I fitted the Kevlar clutch linings bought at Oley and the 25 tooth ‘speed’ drive sprocket, and put the bike on my new local dynamometer, having moved house since the last dyno runs in 1999. The bike roared away, pulling strongly over the rev range and showing about 36 bhp at 4600 rpm - just like the 1934 brochure figures, except at the back wheel rather than the engine. I put the bike in my van and, next morning 16 August, drove it up to Woodbridge airfield in Suffolk, another of those disused Ministry of Defence properties open a couple of days a year. It was another glorious summer day, but the bike was standing in a pool of oil when I took it out. The dyno run had vibrated out some of the tank fixing screws, separating the tank halves and cracking the nipple taking oil to the mechanical pump. Application of duct tape and baler twine in the classical fashion stemmed the flow, and I was able to convince myself that splash lubrication was probably more important on these short runs anyway. After scrutineering, we lined up to take our turns along the full length of the runway and into the speed trap towards the end. In fact some of the modern bikes started in the weeds of the taxi way and weaved through onto the flat tarmac surface for an extra runup.

There wouldn’t be many runs that day and I wasn’t going to spare the bike. On the first run it was into first gear, rev the bike, let out the suicide foot clutch when given the all clear signal, tear along in first, drop into second, then into top and tuck in with head down and throttle open. My first run was timed at 99 mph, so I removed the front plate carrying my race number, thinking this would reduce wind resistance. But the second run was also 99 mph, so I was maxed out at 4800 rpm and past the peak power point for the bike. In fact, I was repeating Connie Schlemmer’s 1935 run, when he told me he took a 1933 VLD to 99 and 97 mph speeds, timed with trip wires and stop watches on public roads one weekend. As a consolation, I took my stock 1930 VL up the course a couple of times, running a 23 tooth drive sprocket and fitted with crash bars, saddle bags and a bronze Schebler carburettor. I thought 79 and 81 mph perfectly respectable, but you could feel the early T-shaped manifold did not have the top end power of the hot Y-shaped one introduced with the VLD.

Now it was time for quarter mile sprinting, so I changed to a 22 tooth drive sprocket and had three runs at that. The ’34 managed 16.5 seconds/81.2 mph terminal speed into a slight headwind, so this is the gearing I shall use for future events. The ’30 managed 19.3 seconds/ 66 mph, which was comparable with the first outing of the 1934 bike four years earlier. But then I heard there was to be a short top speed session in the afternoon, so I stopped sprinting and brought out the big guns - the 27 tooth drive sprocket and 92 link chain I had had made a few months previously. When tested out on the street, this combination is hard to manage as it shows a big gap between second and third (top) gear. However, it must be worth a try for the 35 minutes wrenching (again) required to remove the primary cover, loosen the chains, change the sprocket, and readjust everything so the chains, rear brake and wheel alignment are still in specification.

Down to the end of the airfield to line up, wait for the signal, then cane down the runway centreline to end up between the chequer boards and the timing gear. I returned to the control hut to pick up my ticket, and found I had done 102 mph. Yes! Four years tinkering and trying to find suitable venues had finally paid off. Then back to the start, with the tanks now held on only by the rearmost screw and the pressure of my knees at the front. A Hayabusa had hit a crosswind and clipped the timing lights at 220 mph, so there was a delay followed by a call for a volunteer to check the set-up. That was me as the sun headed downwards and the day came to a close. The go signal, drop into first gear, plenty of revs, change gear and max it out (70 mph in second!), then the long build up in speed as I tried to tuck myself even more into the bike and make sure the throttle was wide open against that strong return spring. The rigid front end was surprisingly steady, with no speed wobble, and I felt I’d found something extra this time. It was 103 mph on that run, and no time for any more. There is the electronic ignition to fit, and those aluminium heads when they are finally done, and a little more compression ratio should give more power without strangling the gas flow. How about separate exhausts, or retubing the frame in a lighter material? Next year 104 mph would equal that old Harley record, and 105 would beat it. In the meantime I’m satisfied to tick off this goal that took four years to achieve, and look back with respect to those throttle snappers scorching across the California sand seventy years ago.