I have a JHA kit and when I first installed I did not use the X & Y tubes. What I noticed on NSR-WORLD site is that one end of the X is left open to the air. Does it matter if it is attached to the line going to the air box ? Or should that line just be eliminated ? I have installed them, but attached the X tube to the line going to the airbox T line.
Can anyone describe how these work and what they do and when ? _________________
The Jha kit, like the HRC kit (same same) is designed for race use, so does not have an airbox.
The line that would normally go to the airbox should be tucked into the spare parts box. The same goes for the hose that normally goes from the airbox to the inlet of the air solenoids.
Note that the part of the X piece that is open to the air is the bit with the brass jet fitted.
StephenRC45 has been playing with PJs recently in a quest to iron out the fuelling on his MC18; so far we have come to the following conclusions...
The PJ circuit has 2 main objectives:
1. To richen the mixture at predetermined (by the PGM?) engine speeds/throttle openings
2. To provide fuel to the crankcase on over-run during closed throttle situations
We also think that on a stock bike the PJs are used for extra top-end fuelling, thereby allowing the use of a smaller MJ and consequently more control with the JN, of the mid-range fuelling. On a stock setup the MJ acts almost like a "mid-range" jet, and the PJs like a top-end "booster" jet in conjunction with the MJ.
The HRC/Jha kits blank off the PJs and so as I see it, the X and Y pieces act instead as a secondry air bleed. The HRC and stock X and Y pieces are significantly different enough to make major adverse changes to the jetting process, so therefore you will need to make your own conclusions how to best try and integrate them in to a non HRC/Jha specified setup as they were never intended for this purpose.
Hope this helps. _________________ Andy.
NSR-WORLD.COM
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Andy, by PJ do you mean the power jet or pilot jet? I'm presuming the power jet. I'll stick with PwrJ for the power jet and PJ (some use SJ, slow jet) for the pilot jet.
Anyway, the PwrJ is not controlled by the PGM and has nothing to do with the air solenoids. The PwrJ is controlled by the pressure drop caused by the velocity of the intake air. On an MC21 at say half open throttle the air speed is such that the pressure drop at the PwrJ opening sucks the fuel up high enough to bleed fuel into the air stream from the PwrJfirst hole. At WOT the air velocity is higher, so the pressure drop is greater and fuel is drawn from both PwrJ exits. There's also no 'switch off' so the higher the air speed, the more fuel is drawn, up to the maximum flow of the PwrJ fitted.
When you shut the throttle, the PwrJ don't flow.
The air solenoids and X and Y joints control air flow to the emulsion tubes. The solenoids allow extra air to flow at lower rpm to clean up the bottom end. This works closely with the PJ and needle straight diameter.
When you're on a high speed run, WOT, the fuelling is being taken care of by the MJ and the PwrJ. When you slam the throttle shut and get on the brakes to avoid that car pulling out in front of you, you're relying solely on the PJ to stop the thing from siezing up. bit of a worry eh? Now you know why good 2T oil is important!
Jetting's never easy, and takes a long time to try and explain fully.
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