l-o-n-g inlet manifolds

johnm said:

14 inch would tune third node at 6250 rpm and fourth at 4900 rpm.

My Dommie is tuned with 13 inch inlet tracts at about 6800 third node and 5250 fourth node.

John

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So what do fou figure the length should be for the 2nd node at about 6800 RPM (and is this the length from the valve at 32mm inlet tract diameter all the way?)

So what do fou figure the length should be for the 2nd node at about 6800 RPM (and is this the length from the valve at 32mm inlet tract diameter all the way?)[/quote]


lenght for the second node - about 17 inches. If you want to follow the Diamond Vizard formuale it is much longer at 20 inches.

The lenght is from the valve to the bell mouth opening. Not the carb main jet.

Valve head ( face ) to mainjet was 14 in on 32 bore , on Deans set up in picture , I believe . Pretty well puts the flange under the X brace , in a Commando . ( Mk 1s ) he ran Mk IIs , think he eventually went to 34 .

Matt Spencer said:

Valve head ( face ) to mainjet was 14 in on 32 bore , on Deans set up in picture , I believe . Pretty well puts the flange under the X brace , in a Commando . ( Mk 1s ) he ran Mk IIs , think he eventually went to 34 .

Click to expand...

So I would guess with 14 in valve to mainjet the full lenght to bell mouth exit will be approaching 16 to 17 inches. So tuning to second node (unless he is reving a long way past 7000 rpm - which he may well have been !!!!!!!)

I saw Deans ride the Commado at the Cemetary circuit lots of times. The only Brit bike in a sea of Kawasakis!!!!!!!!! Those were the days when they had H2 only races and RD 350 only races. One of my friends Bill Biber used to be in the middle of it as well (on his H2).

From what I know the best length far all around race power is about 14" from the valve or 10-1/2 from the head to the end of the bell mouth. This is from Leo Goff & Ron Wood & all their dyno tests. 16 to 18" gives you the most power (1st primary wave) according to Jim Comstock. But the power band is too narrow requiring variable length velo stacks. The oil tank has to be below the carbs in this case.

Peter Williams used 12" from the head to the end. Add about 3" from the head surface to the valve.

Just for idle :lol: comparison . 56 LeMans .


Pity we didnt do a bit better durability wise motorcycley in those days , Then again , youse gets wot youse pays for .

Are you sure Garner knows that?