It’s not been the best couple of weeks for getting on with the Super Squirrel racer’s engine with both my wife and little girl both poorly and work being very busy indeed. A very good friend of mine also passed away, although this did rather contribute toward the quietness and patience required for gas flowing with riffler files.
So what is the plan?
A bit of history… In 2006 I finished re-building the old Super Squirrel racer and into it went a good Scott engine that I’d built with Moss crank. I sold this engine to fund another more radical engine build, and machined up my own head and heavily modified a Scott barrel to suit. I also welded up my own expansion chamber.
The crankcase I used had been a damaged case that we’d had welded, but had some evidence of cracks still remaining beyond the welding.
Anyway, I took it to it’s first BHR meeting at Mallory and it felt really strong for the first two laps, before it died. I didn’t really look at the engine until I’d pushed it back to the van, but when I did I realised that the damage was absolute to the crankcase. It was split in two and completely irreparable.
Upon reflection, the case wasn’t up to the job. I might have had some tiny amount of piston/ head contact too.. I know they were close as I’d had it before during testing and had worked to increase the clearance. The main bearing assembly was experimental and I think that also may have been a weakness. You live and learn and competition sometimes just brings the answers a bit quicker.
I had been working with my dad building the engines for a few years and I think this just happened just as I was going to move on to do a contract working to changeover a cylinder head line to a new head in the casting plant at Nissan in Sunderland. As I was not in a position to build another engine, my dad resolved to machine up one of his crankcase castings to at least provide a sturdy basis for a race engine. Into this he built the internals of the previous engine, and the new engine was badged ‘Phoenix’ in reference to it’s resurrection from the remains of its predecessor.
It was a fantastic thing to do for me.. I think because he felt quite sorry as I’d put so much work into the previous engine and also, that he felt that the far stronger crankcase casting was a far better place to start.
So I ran the engine for a couple of years, on petrol, and it kept going, but it wasn’t really competitive. It wasn’t really ‘tuned’, just solid and although I really enjoyed my bike, it wasn’t anything like as good fun to ride as my dad’s Flying Squirrel, which just had a sense of thrilling urgency that mine lacked utterly.
The catalyst for the major improvements that came was when my wife and I received a wonderful wedding present in 2011, in the shape of a new expansion pipe that my dad had made to fit by Gibsons exhausts in the South East. My wife found this quite amusing. It was somewhat better looking than the one I’d welded up myself.. but did it work?
The first test came early in 2012 when we participated in the Prescott hill climb in aid of the blood bikes. With the same jetting as previously used with my old pipe I accelerated from the line hard and then pulled in the clutch quickly as it seized on the needle as I rolled it off.
We played around with it in the afternoon, changing plugs, altering the timing and jets but it just seemed to be running very hot. The next outing was at Lydden with the BHR club and we put in an extra head gasket to decrease the compression. It was still running a bit hot, but better… at least it finished a race. It really wasn’t quick enough though. I realised that I needed to make a decision.
It may be that the exhaust is not of the optimal shape and there may be a build up of heat because of this and not simply because it’s charging the cylinder so effectively… but we are not running a blank cheque development program (!) and so we needed to try and see if we could get it to work.
I figured I had three obvious choices. The first was to put my pipe back on. I did not want to do that .. It seemed such a retrograde step. The second was to work on getting the heat away. I’ve got a speedway radiator in the bike so a bigger one may well be much more effective. Also my dads bike has an aluminium cylinder barrel which also transfers the heat away from the exhasut port and cylinder head much more quickly than my iron block. Great. A new radiator would be about £1000 and a cylinder several hundred.
The third way was not popular with my dad.’Dope’ I said, that’s what I’m going to do, ‘run it on dope’.
The positives of methanol are that it really cools an engine and allows a far higher compression ration to be run than with regular petrol. Methanol also burns more slowly and that can make for a smoother and more progressive power delivery. On the negative side, it’s comparatively harder to get hold of, more dangerous to deal with and you need a much larger amount to run on. I’ve also experienced lubrication issues since I’ve used it, but it may be that some careful development may improve that. It also doesn’t give much warning in terms of plug colour if you are running lean. It tends to let you know by melting a hole in a piston apparently.
So it was that I invested in a barrel of your finest methanol and talked to a few people who had experience using it. By far the most useful contact was Roger Cramp, who used to race the highly developed Velocette that his son Ian now campaigns with the BHR. He had been involved in the building and development of an ariel leader that he had run on methanol as well as a Greeves. He confirmed the research I’d done about the necessary changes to ignition timing but also said to be aware that methanol was singularly averse to atomisation (at least when bucketing it in) and that high intake gas speed really helped. This encouraged me to stick with my smallish single carb to at least try out and see if it worked.
I decided on a huge 980 main jet and then measured the needle jet with a taper pin. I then put the carb together and drew lines on the needle at 1/4, 3/4 openings at the top of the needle jet and then worked out the dimensions of the needle at those points against the aperture open for air inlet. I ended up with a pretty severe taper on the needle, but it seemed to make sense.
I advanced the ignition by about 7°, closed the plugs right up and pushed. It fired up and it ran, albeit a little roughly, before I put it in the Van to took it to the last BHR meeting of 2012.
It was brilliant. The jetting seemed to work fine and there were no holes in the power delivery according to throttle position. The bike pulled and was so much fun. It felt totally different to my dads bike, but the torque and flexibility of mine suddenly made it feel like a completely different bike. It absolutely hammered the clutch though (as it does tend to with three gears) and I was up to 1am on the Saturday night stripping, releasing, filing plates and and rebuilding it.
2013 came and one of the first jobs I did was to rebuild the clutch with new GFS plates, laser cut. They were perfect really because I had to dremel each one to fit with abut 0.010″ clearance. The less clearance, the less hammering… My dad also had some pressure plate he’d had made out of solid, which didn’t flex like the original ones. These didn’t have the adjustable clutch actuation pins I normally used, which are a pain to set up. I made pins up instead from some silver steel and got them within 0.001″ of each other using a cordless drill as a chuck, a file, a dremel and some emery cloth.
We took it to a couple of track days, and then the last Cadwell park in 2013 and (with new 21″ racing tyres robbed off my dad’s poorly Flying Squirrel) managed a couple of second places and even a fastest lap. It was flying, although not in the league of Mike Farrel on his Rudge, who was really out on his own and un-catchable for us at least. You can lose a lot on the start as it’s difficult to get off the line with three gears when you’ve geared top for a long straight. Except for a CS1 Norton belonging to the famous Lewis family who’ve been campaigning Triumphs and the Norton for many years. I think everyone else runs four gears. It does make a difference.
I ended the weekend having blown three composite head gaskets and with the feeling that there was a bit too much piston slap noise, but apart from that it was the best racing weekend I’ve ever had at Cadwell. I also knew I needed to strip the engine and that I’d do some gas flowing whilst it was apart.
And that’s where we are!