BW
Do you use a more modern grind in your GT ?
Something I tried was just install a 230 @ 0.050 exhaust lobe. No computer changes.
Thats 35 degrees of duration split. Try it sometime. You will like the results. No other hang on parts and I
changed it without taking off the tank or changing the oil..
Hi Pete, with the Bullets, I stopped getting too engrossed in the numbers quite a while back and I found that the most impressive and / or aggressive looking cams were not necessarily the best. I also, out of sheer mechanical necessities, found that deviating from 'ideal' timings to some which gave a little more 'wiggle room' for the valves and the very lumpy pistons I use in our racing Enfields actually improved the performance, which was unexpected. It didn't take me long to try this on an Electra X I tuned - Asbo 11 - where I had been uncomfortable with the relationship between the piston and inlet valve proximity, when going over the 'other TDC', when the Redditch 'S' profile cams were timed 'on the marks', and this machine also gained a little speed and revved higher as a result. The latest 'Asbo' machine - number 41 is also an Electra X and this also runs a set of Redditch 'S' cams, with the inlet retarded by 1 tooth off the marks, not for the same reasons, as I cut the inlet valve seat back and could have run on the timing marks, but to liven it up. I am fully aware I am moving the inlet timing by a whopping 18 degrees, but it seems to work.
More recently, on the 535GT machines I have tuned - two on the road and a third done, apart from cams which are on back order - I fitted a set of Hitchcock's cams to both completed machines, one green [Asbo 24] and the second yellow [Asbo 33]. Both are identical, with carb conversions and their cylinder barrels shortened by just over 1 mm as required to get the squish clearance right and push the CR up a little. The only difference is the green one has the cams timed to the marks, while the yellow one has the inlet cam retarded by 1 tooth, due to possible piston / inlet valve contact issues, which I put down to slight valve seat depth discrepancies, or possibly machining variations on the timing side mainshaft integral gear teeth. I was a little sceptical about this working with a set of 'out of the box' go-faster cams, but to my surprise and delight, the yellow bike turned out to have an edge on the green one and was definitely more, shall we say, 'angry'.
I assume the ignitions, power commanders etc were all as factory, but cannot confirm this for certain and neither had a standard exhaust fitted, as they arrived, but they both went home a lot faster!
My cam philosophy these days comes down to getting as much [but not the most] lift as required, for as long as possible, while keeping the valves away from each other and the piston. I honestly gave up logging the numbers and degrees quite a few years ago now and literally time my engines by look and feel!
B.W.