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Amal pilot jet sizing

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After buying a new pilot  jet  size 30  to replace the 25  that appears too small , I find the 30 is far smaller than the 25 !  .looks like I will be  making my own . What exactly does the 30 represent  . perhaps 3 thou ?.

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25 and 30 refer to the flow rate in ml. So the 25 flows 25ml of fuel per min.

In fact the flowrate for pilot jets can be equated to a size, 25 jet is 17 thou, 30 jet is 19 thou. Once you get to main jets then exact sizes cannot be set to a size as the shape of the hole and markings from the drill cutting have an affect so flow rate is the sole measure.

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Hi Robert. Also make sure that the jets are genuine Amal. I’ve had some non-genuine ones that are a mile out of spec. The genuine ones have rectangular cut-outs across the hex sides of the jet.

Regards

Tony

 

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After a close examination of my new 30 pilot  , I think its a pattern part and  I have had to pass an 18 thou bit through it to clear away swarf. . I will  let you know how it runs and if it helps the by pass supply  deal better  with the progression from pilot to slide cutaway.

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Well that worked. The uneven and unreliable idle has gone and the spit back with it. whether its due to the bigger pilot or perhaps a minor restriction in the 25 its hard to say. A session with the colourtune and a warmed up motor  is next.  Its only taken a whole riding season to sort this, what chance anything complicated?.

 

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