single carb conversion

Fast Eddie said:

Jagbruno said:

MrNorton said:

Or maybe i must buy JSM motorsport dual Keihin set for Norton.
I have PW3 cam and portted cylinder head,so i don´t know how Jim can jetted correct that set for my bike.
When i have looked cases whera are installated VM36 on Norton,almost everyone has diffefent jets,needle etc...

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I also have a PW3 on my 850 Featherbed racer, I tried dual Mikunis before going back to dual 32 Amals with 260 main jets. Starts first or second kick, goes like a rocket. Clocked at 210km/h-130Mph.

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What compression ratio are you running in your featherbed racer ?

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9,5ish.
But...lightened and balanced crankshaft, lightened Dunstall rockers, flowed head with splayed manifolds, lenghtened box section swingarm, Dunstall silencrs, full Dunstall fairing...easily revs above 7500 with a 22 sprocket...

jaguar said:

I kind of fall into the "why" camp.

The Amals are stone axe simple. Balancing should not be scary to someone that wants a vintage motorcycle of any kind in their life.

IF you really are struggling with the stock carbs, maybe there is a real issue that you should sort. Maybe the slides are bad an you need to replace the carbs?
From what I have seen you can buy two new Amals for the price of the single Mikuni conversion, so what is the point?

But I also don't see why points should be replaced on a stock bike with electronic ignition either.
Maybe I am odd.

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Maybe I am odd as well but you will find a lot of comments about failed ignition units. They are also quite expensive and I find that electronics can be very unreliable not like the simple mechanical points that have been used for decades with great success.

Just got back from my first real test of the 34mm Mikuni that I installed on my stock 73 850. It exceeded my expectations. 48 miles of twisty Whidbey Island roads in 38-40 temperatures and I'm happy but a little cold. Seems to be slightly less slow from idle up to about 3800 rpms and maybe a bit slower above that. It pulled a long grade at 80 without a problem. I did see a top speed of 90mph which is immaterial to me but I just had to see if it would do it. Settles down to a nice even idle much better than my twin Amals did. Very smooth and predictable when rolling out of corners. Works like a carb should. When my Amals were new and freshly tuned they too worked flawlessly but since they were getting worn it was either time for a sleeve job or a replacement. Always wanted to try the single Mikuni so I'm giving it a one year trial. If at the end of summer I find it less tasty I'll score a set of the Amal Premiers.

MrNorton said:

Or maybe i must buy JSM motorsport dual Keihin set for Norton.
I have PW3 cam and ported cylinder head,so i don´t know how Jim can jetted correct that set for my bike.
When i have looked cases whera are installated VM36 on Norton,almost everyone has different jets,needle etc...

Click to expand...

I tried jetting the Keihin CRS dual kits for 750s, 850s etc. But there seems to be little (or no) jetting difference needed for different motors. It helps being simple with only one throttle cable and no need to synchronize.