How many Norton (or other) heads have you reworked over the years, to get to this level of knowledge? As not every step is a step forward it must get frustrating at times.
As not every step is a step forward it must get frustrating at times.
I am not sure what the advantage of the twingle motor would be. I guess more traction is the idea. I sure don't like the idea of it for the Norton. It would be pretty hard to kick over! I have a 75 Ducati 900ss. The previous owner had converted this machine to a Twingle. I didn't realize this when I bought it. There was a bit more vibration and something didn't quite feel right. The sound was different. The think is with the Duc though the two firing inpulses were still 90 degrees apart. I was able to put it back to standard in about an hour by removing the front head and turning the engine over a few times to get all the dots lined up as they were originally intended.
I am sure your Norton engines are putting out more power than this 900ss. Apparently they put out about 68 HP at around 7500 RPM
comnoz said:And here is what you get when something isn't quite right. Yours is the blue line along with three of the heads I posted yesterday . Time to go back to the porting bench and figure out what is wrong. Jim
hobot said:Why not down size the twingle's jug sizes to up the rpm & gearing to a tolerable deep thumping Commando one of a kind hoot. Might need a heavier flywheel to work nice.
Fast Eddie said:Jim,
I've just read this entire thread for the 3rd or 4th time (my Missus really thinks I've lost it!) and our email exchanges, and I'm sad to say, I'm still not really clear on a few things!
It seems that for hot street use there are a few 'choice' options:
1. A stock FA head: this compared very favourably with some good heads, in particular with regards to inlet velocity, which you said is key if you want a wide powerband.
2. A ported FA head with stock valve sizes: this just performed better at everything over the stock head.
3. A RH10 with re-angled 3mm oversized valves and your new 'cut' to the seats and valve: gave brilliant flow results (despite you previously thinking it would not) but you didn't post velocity figures.
>generally yes<Fast Eddie said:Due to the cost / benefit, it seems that a FA head with the full oversized valve work to be for serious racers and / big engines only.
Fast Eddie said:So Jim, by way of a summary, or conclusion, could you please post a graph for flow, and a graph for velocity, to compare the 3 heads described above? And perhaps a stock RH10 as well, just by way of comparison?
Fast Eddie said:It would really help me decide my next course of action, and I imagine there are others in the same boat as me!