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Balancing on throttle bodies


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I have a 150 Superlight - Ford Sigma Engine.


Idle was running too slow so I have adjusted the allen head screw on the main throttle body to run at just under 1000rpm which seems ok. 

There's a second adjustment allen head with anti vibration spring to balance between the throttle bodies - does anyone how is this best adjusted to make sure they are balanced? Any decent video or protocol online?

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Take air filter off

 Check  WOT achieved and is the same on both throttle bodies with engine OFF. With engine warmed up and running and throttle closed, listen with a length of tube down each trumpet...should sound the same


Make and use a vacuum gauge ( plate with breather hole  and small bore tube + water) at closed throttle with engine running. DO NOT blip thottle or water will go in engine! 


Buy a flow meter/syncrometer (lots available from your local website)


Balance on centre screw, set revs on end screw, set throttle pot...and again....and again....etc.   Best of luck, they are a pain to get (all 3) right but it passes the (a lot of) time!

Note:-  I have seen several Caterham throttle bodies which are not machined or matched as a pair or matched to the head ports. These cannot be properly balanced without a lot of fettling and realignment.

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