I am going to write a piece for yowl about all this but i’ll give a brief rundown of the progress…
After the crankcase failure at Mallory on the 8th April, and bearing in mind that i can’t just work on my own bike(!) i left the majority of the work until the week before which i dedicated entirely to the project.
After completely remachining a modified birmingham case to suit ball race mains, grinding up a pair of new crankpin bushes, re machining the high flow transfer ports and sorting out a replacement for the broken piston i’d sustained plus obviously the subsequant build …i was only to try to sort out the carburation, which had been totally off at mallory.
We in fact completely changed the fuel feed system design the day before oulton and had decided to run a single top feed float chamber to both carbs for the ease of installation and also the fact that i was uneasy about having the left hand float chamber rammed up against the exhaust(!).
I finished wiring the last nut at 7.00pm on friday night and stuck it on the trailer without even having the time to start it…
Saturday morning arrived and with a certain degree of anticipation, it started. It became obvious immediately that the squish clearance was still too close as we could hear a faint hammering on the overrun.
it wasn’t so bad however and thinking it might settle i went out to practice.
I came back smiling. Considering this engine is a totally different configuration to Rogers in all port timings except transfer, it has been a exercise in development that has seen a great deal of research and of course wild speculation.
It seemed really quite quick, and considering that i was wearing the wrong gearing and that we hadn’t even begun to refine the ignition timing (which we decided to initially set at 20 BTDC) or the carburation, or even the exhaust, which was made to suit a different port timing, i was significantly heartened.
Race 1 was in the wet. I haven’t ridden at Oulton for 18 years (amazing to think) and yet, I was holding forth for at least a couple of Oultons long laps before i went down at the chicane.
more like falling over than falling off at that speed and indeed there were three of us sitting together by the end of the race.
I was told that because Oulton is a favourite car track, the surface gets a bit rubber impregnated and so is a little tricky in the wet.
No Damage worth speaking of to the bike though .. and i was fine so that was just a reminder of what can happen.
The next race was plagued by difficulties after i missed a gear and it became obvious that the hammering in the top was only going to get worse. I ended the race on one cylinder, and although i did consider going out again after sorting the firing problem,Roger offered me some truths.. that at this point i could probably rebush the little ends and reuse the pistons but that if i continued it was likely to end in worse damage.
So, knowing he was right, that was that.
We were visited by a number of fine supportive Scott people and i hope that they enjoyed their day, despite our problems.
It is easy to keep something going if you stay with what is known. Rogers racer was developed until the early seventies when he took a powerful configuration and applied it to a chromed aluminium block. After that, theres no real port development possible, though to be honest, It works very well! The thing with this Iron engine, is that its timings, exhaust, carburation and head type are different to anything we’ve run before. The squish clearance was tight because i was trying to see how close i could get. Another 0.015″ to 0.020″ will undoubtedly cure it completely.
We have decided now that its next port of call will be the dyno and then we can see what is possible…
Thanks for all the support…
I’ll update on all future developments
Top story again Rich! It’s a shame we are not in England as we would certainly have come and have had look at you and your bike in action!
Keep up the good work!