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Mikuni Jet Sizing

Started by racerrad8, August 23, 2018, 07:19:56 PM

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racerrad8

#15
August 25, 2018, 12:12:52 PM
Quote from: Pat Conlon on August 24, 2018, 04:02:57 PM
Randy, I found this image showing the profile on the different Mikuni pilot jets. Does this appear to be what's going on?



Yes, that is the two jets I have. The jet for our FJ is on the right and the "193" jet is on the left. Since they both have the same external dimensions and seat at the bottom taper, one would think if they were both marked "40" they would have the same "metering orifice" size.

But that is not the case.

Randy - RPM
Randy - RPM

racerrad8

#16
August 30, 2018, 12:34:14 PM
Mike Ramos stopped by this morning with a complete set of plug gauges ranging from .0110 - .0605.

Here are the measurement differences between the two "40" pilot jets.

Fuel Pilot Jet 4HR-14142-40 is the "40" jet we use in the FJ carbs.  - .0140" (Hole on the right)
Fuel Pilot Jet 193-14242-40 Pilot jet that is larger and won't work.  - .0225" (Hole on the left)

Now if I could get someone from Mikuni to explain how the two jets marked "40" have different size orifices, then the mystery would be solved

Randy - RPM



Randy - RPM
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