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06 kx250f jetting trouble on jardine rt-5

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ok i bought a jardine rt-5 full exhaust system and i am having trouble.ok i am running the stock jetting of 180 main and 40 pilot only because thats what jardine sugested but my bike had a 170 main and 40 pilot in it with the stock exhaust and i live in tn so i think this is how the kawasaki dealer set it up.Any way with the 180 main and 40 pilot it is popping like crazy and my fuel screw is on 1 3/4 turns out.Basically when i start the bike and get on the bike to ride it it pops alot from the start of the throttle to half throotle or less i have not really took it more thank that cause it pops so bad in that area of throttle.Now with this jetting set up like it is i was riding the bike to see exactly where the problem was on the exact throttle postion and it dies on me and i aint been able to get it started again yet and this happened yesterday.It trys to start everynow and then when kicking it but thats it this is the first time this has done this since i have had this pipe and trying to jet it.Also i dont even have a 1 hour of time on this motor after a complete rebuild and it is starting to make me real mad.This is my first time tryin to jet a carb too.I found some good starting points from team green and pro circuit that i think im about to try for a starting point cause since jardine told me to put the 180 main in the carb it has been trouble.I mean it wasnt this bad with the 170 main i had with stock exhaust and jardine saying a 180 main is good that cant be right as they are located in california and im on tn.Well team green settings are 175 main 42 pilot stock needle and i believe 3rd or 4th pos on the clip.I just dont understand why my bike all of sudden died and cant start it after ridin it to see how i need to jet it.Please let me know what to do or a good starting point cause im tryin to save money by not taking it back to the shop as i spent 1200 on a rebuild there

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  • 1 month later...

Popping with an open pipe is normal. No muffler to absorb the pops so you now hear them.

Why your bike is not starting is a slight mystery. Main jet has nothing to do with idle/starting. Bad fuel? Dirt in the pilot jet? What else did you 'adjust'?

Instead of changing jets because someone says so, you must test and see what actually works for you.

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

Main Jet

Starting with the recommended main, remove the airbox door and go for a ride (bike fully warmed up). Is it better or worse?

If it is better, you need a smaller main.

Go down one size, replace the airbox door, ride. Remove the airbox door and test again. Better or worse? If better, go down a size again. Keep repeating this till the test with the airbox door is worse.

If it was worse with the airbox door removed, tape over 1/3 of your airbox opening, test (airbox door on, of course).

If it is worse now with the tape and was worse with the airbox door off, your main is just right. You are done!

If it seems better, you need to go up a size in main jet. Then test it again (remove the tape). Replace the tape, test again. If with the tape on it is better, go up another size in main. Keep repeating this till having the tape on is worse than with it off.

To finish up and ensure you are set accurately, retest the bike with the tape off (airbox door on), ride it, then remove the airbox door (tape off, of course). Best performance should be with the airbox untapped, airbox door on.

Remember, the main only operates at WOT. Ideally, you want to be in 3rd or 4th gear doing the tests, hitting max revs (just shy of the limiter) for at least 10 seconds to get an accurate representation of the jet status.

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