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Discussion Starter #1
Hi
long or short bellmouths for amal 930 (T140v 1978)? What differences would be noticeable between the two? I could fit the shorter ones without any modding, thats why I ask.

Anyone been there?
Cheers
R
 

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The shorter ones do nothing,except collect a bit of dirt before it enters the engine.
Longer ones,if they are a closer match to the carburettor bore,will do something. Google "best bellmouth Gordon Blair".
Its usually better to extend the intake on the manifold side.For best results below 6000 rpm,you need 15" from intake valve to carb mouth/bellmouth.There is a shorter,but less effective alternative of 12".
Any increase in intake length usually helps;you're not likely to exceed 15."
 

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I made some new filter panels and fitted the Amal long type.
As yet untested :eek:
But at least the sliders are visible.

 

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Very nice looking set-up Caulky, really nice.
Ron
 

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Hi R,
You can calculate the required length of your intake (From Bellmouth Intake to valve seat) by using the formula below:
L=aC/RPM

a= wave speed (speed of sound) = 346 M/s @ 25°C, 343 M/s @ 20°C, 340 M/s @ 15°C
C= 8900 1st Harmonic
6600 2nd Harmonic
5150 3rd Harmonic
4150 4th Harmonic

For example 345 (Speed of sound @ 22°C) x 5150 (3rd harmonic) / 7000 (RPM) = 253.82mm (Which is about 10")

If you measure the inlet tract length from the end of the air intake to the valve seat using Caulky's velocity stacks you measure exactly 10" so it proves that AMAL must have done their homework :) (I know, after seeing his post I bought the same ones:))

If you input the 2nd harmonic (5150) you get a length of about 13" which looks about the same length as the long intakes shown in Stan Shelton's book "Triumph Tuning"

If you where to try using the 1st harmonic you would finish with an impossibly long intake.

As for using the short bellmouths, they would do nothing without extending the intakes. Mr. Pete is correct in what he say's, try using the above formula with different RPMs and harmonics and it will prove exactly what he said.

I hope this helps

Webby
 

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Is there an aftermarket panel available for an OIF T140?

I would like to fit bellmouths but I don't want anything too Heath Robinson
 

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Is there an aftermarket panel available for an OIF T140?

I would like to fit bellmouths but I don't want anything too Heath Robinson
Hi Dave,tms-motorcycles.co.uk list aftermarket plastic panels for OIF Triumphs they do away with the airbox altogether, £22 +vat +shipping,
regards,
Bill.
PS forgot to mention this price is per side.
 
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