The genie jets are ok in terms of how they measure the jets; they measure the exact cross sectional area, even if the hole is oval - this is where they are much better than using pin gauges to measure. BUT flow is the best check. If you are a bit handy making bits, make a flow rig from a 1M tube, jet holder in the bottom, electric solenoid water valve connected to a digital timer, water up to 1M in the tube or to exact same point in the tube - can be done with a decant / drain hole to the side so the exact same amount of water goes in every measure, start the timer - usually to allow water flow for about 40 seconds, catch water in a little dish, weigh the water on a little digital scale, record weights in grams, lowest weight is lowest flow - highest weight is highest flow, that gives you a perfect linear comparison between jets. I priced up the bits and the came to about £50 and you can do unlimited sets of jets. Then we retired!!
So least accurate is do nothing - follow the numbers on the jets, next use pin gauges, next very accurately measure the cross section area of the jet hole / oval, flow test with water, finally if you are really anal flow test with petrol oil mix as that has a different specific gravity and viscosity to water! If you don't put the effort in you don't get the results!!
Note the guy whom told me about the flow rig in extreme cases he found jets with a bigger number flowing less fuel than the next number down!! But in most cases the increase in flow was not linear with the number increase.
The other way is to test on the track and get a feel for what specific jets do - but don't mix them up with other like numbered jets or you will loose your test data!!
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