ALLEN MILLYARD
He’s finally finished his RC374 homage.
Here it is, finished… Allen’s RC374 six-cylinder racer-replica
My RC374 was basically finished and assembled in bare metal. I had run the engine several times and it was running really well.
I had rolled down the drive a few times and it felt great. It’s such a small and compact bike, I found myself wondering how Mike Hailwood rode his RC174 around the Isle of Man TT circuit at speeds of up to 150mph in 1967. Standing back and looking at the bike, I thought it would be nice to leave the fairing in its raw aluminium finish complete with hammer marks, rather than painting it silver, but wondered what to do about the yellow stripe and blue race ovals. I didn’t really want to paint them on, so I decided to make them myself from self-adhesive vinyl shrink-wrap, which is normally used to wrap cars. This proved to be perfect for the job.
I first traced out the outline of the stripe in pencil directly on to the fairing using my reference book photos as a guide, and then I used some black pin-stripe tape to mark out the final shape. The outline was then traced on to a sheet of paper and cut out. I used this paper shape to mark out two mirror image shapes on the vinyl wrap and cut them out with scissors. The vinyl cut-outs were then applied to the fairing, one each side. The blue ovals were drawn directly on to the vinyl and cut out, before being positioned on the fairing. The next thing to do was to take the bike apart and get the frame, tank, seat cowl and mudguards painted, and the bright parts zinc-plated. I had used stainless steel nuts and bolts wherever I could, but a few items like wheel spindles springs, brackets and clips would need to be plated.
All the parts that needed painting were
taken over to my friend Neil Howarth’s workshop, I have known Neil for 24 years and he has painted just about every bike I have made. Neil is well known for his quality paintwork, but what impresses me most is the durability and scratch-resistant finish, which Neil says is down to his meticulous preparation and choice of materials. Many of the cars and motorcycles he has painted have won concourse awards at the highest level in the world, including a vintage Bentley, which won first place at Pebble Beach concourse d’elegance in California.
I arranged to meet Neil on a Monday morning at the yard where he does the sandblasting. In the middle of a cold snap, aptly named the ‘Beast from the East’, it was sub-zero all day, with blustery wind, snow and ice. The sand-blasting plant was frozen solid, and so were we, but after half-an-hour we got the 1970s compressor started and set about sandblasting the frame and loose parts to make a good key for the paint. The parts were then hurried back to the warmth of Neil’s spray booth and sprayed with epoxy primer, followed by several layers of undercoat rubbed down in between to remove any minor surface defects, until all the parts had a glass-like finish. The final coat of two-pack high gloss black was applied and baked for the rest of the day.
While Neil was doing the painting, I took all the bright metal parts to my friend Gavin at E Williams Plating (01962 733199) for zinc plating. A few days later Neil called me to collect the black painted parts and the silver painted front mudguard. The zinc plating was also ready, so after collecting all the parts I had everything to start the chassis assembly. The tank and seat were being painted in Kawasaki firecracker red, a really close match to the Honda RC red in my model maker’s guidebook, and which Neil already had in stock. The two stripes on the tank would be masked and sprayed in silver. The whole tank and seat base were then sprayed with two-pack lacquer and baked hard. After a few days, to ensure the tank and seat base were fully cured, they were machine polished to a jewel-like glass finish. I decided to stick the replica Honda wing tank decals over the lacquer so they were not permanent, just in case I needed to change them in the future.
The seat base was taken to Eric at Trimania near Reading (01189 324200) for covering in black suede, in a similar design to the original Honda seat. To minimise the risk of any damage, I stored the black parts on my dining room
table while I started the assembly. It proved to be somewhat cramped at meal-times, but it was worth it.
The assembly started by building up a rolling chassis, then the engine was positioned on blocks of wood under the frame and lifted up so that a rear engine bolt could be placed through the lower mounting lugs and engine. With this long bolt in place the engine, complete with carbs, could be pivoted up into the frame. The remaining bolts were then pushed through and tightened. The control cables were routed and connected up, checking the operation as I proceeded, followed by the wiring loom and electrical components. A 12v battery was mounted beneath the swingarm behind the engine to be out of sight, because the original bike did not have a battery and was fitted with a self-generating magneto.
The six exhausts were carefully fitted, the header clamp nuts tightened and various mounting points bolted up. The rev counter was then bolted in place and its electronic feed wire connected. At this point I needed to programme the internal electronics of the rev counter to pick up a signal from one set of points from the six-cylinder engine (that is one pulse per revolution.) To do this I would really need to run the engine. I had started the engine a few times, but it was so loud in the confines of my garage that I decided to make a simulated ignition system to check and calibrate the rev-counter, because it could take a while to set it up to read the correct rpm. To do this I machined up a bit of scrap aluminium to hold a bearing, set of points and condenser, then made a shaft and cam from a bit of steel rod and wired up an ignition coil with plug lead and spark plug. The rev counter signal wire was then connected to the positive side of the coil and a 12v battery connected up. I checked the rpm of my drill with my laser tachometer and noted the max speed of 3500 rpm, then mounted the shaft of my simulated ignition system in the drill and ran it up to max speed. I looked at the RC374 rev counter and it was reading 7000rpm... exactly double. A quick push of the setting button rectified the reading and it then read 3500 rpm. Perfect!
The tank and seat were now ready for collection. Picking up a freshly painted tank and fitting it to a bike is always an exciting time, but first I had to fit the seat, and assemble and fit the petrol cap and tap. The cap is hinged and the pivot is a M3 stainless steel screw. The release catch is also held in place with a M3 screw, making assembly quite straightforward. The tank is quick release with a rubber strap at the rear holding it on to the bike. The front of the tank slots on to two spigots on the frame, and the tank rests on six rubber pads. I made a rubber chin pad from a solid block of medium-hard rubber using a sanding disc on my angle grinder to shape the edges to fit the depression in the top of the tank, and then held it in place with adhesive number plate tape. The last job on the tank was to fit the petrol tap on to the threaded boss and push on the quickrelease coupling and petrol pipe. The quick-release coupling makes it really easy to remove the tank to work on the engine with no fuel leaks. The fairing slots on from the front in one piece, then nine slotted screws hold it in place, and lastly the belly pan is fitted.
I pushed the bike outside for a proper
look, and was really pleased with the finished result. Stafford show was in two days, so I was pleased I could now take it as a finished bike and not a work in progress rolling chassis. I had a great time at the show, talking to many visitors, and was having tea with Alex George and Malcolm Wheeler discussing the RC374 when Alex said: “Can we hear it run?” I said it hadn’t got any petrol in it, but it was organised that we would start her up in the Classic Racer arena.
First thing Sunday morning I was informed that I was starting the RC374 at 11am. I was worried that I hadn’t run the engine since completing the final assembly. I asked my brother Brian to fetch some petrol from my trailer and take it to the arena. The time soon arrived and I was escorted through the busy hall to the outside area. I carefully poured petrol into the tank and primed the carbs ready for the start. The crowds had gathered and all eyes were on me as I pushed the hidden button. The engine turned over several times before spluttering a bit. It then burst into life with a deafening scream. Alex George came over and took over the throttle. You could see his years of experience handling race engines, as he revved the engine from 3000 to 10,000rpm in short, concise blips.
I then rode the short distance into the marquee and turned off the engine. Although to me it sounded great, Alex whispered that he thought it was a bit ‘off-beat’ on one or two cylinders. I later discovered that Alex was right. I had bought a set of new Patten Suzuki GT380 condensers during the build and they were failing after only a few minutes’ use, causing the points to arc. I replaced them with a set of genuine Lucas condensers such as those fitted to the classic Mini, and the engine immediately sounded much smoother and was even more responsive. I checked the header pipe temperatures with my optical thermometer and all six were within
a few degrees of each other. Problem solved. I haven’t had a chance to ride the bike on a track yet due to its loud exhaust, but I did get chance to ride it around the grounds of Blenheim Palace in September whilst at Salon Privé concourse d’elegance, where it won an award for ‘Most Distinguished Motorbike’. It was amazing to ride with its loud exhaust note echoing off the palace wall, and I was surprised how well it picked up in first and second gears. From a chance meeting with Guy Martin 12 months ago, where I had a close-up look at the Honda RC174 six he was about to ride, I now had my own version. It was a dream come true.
So, what next? Well, next month you’ll see some amazing pictures of the finished bike and news of my next project. cmm