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NEED HELP FAST! RMZ250

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I have a 2005 rmz 250 with a fmf power bomb and powercore 4 slip on. i have been fighting this jetting for three weeks. i finnaly have it where it will idle and not pop and sputter. one thing that has really stumped me is it idles extrely high but when i pull the hot start in it slows the idle down and idles almost perfect. any solutions to this problem?

pilot jet-50

main jet-190

needle-4th clip down

air/fuel screw - 1.25 turns out

idle screw is at lowest possible setting

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You cannot 'jet away' decel popping.

Try a new (not just 'cleaned') #45 pilot jet.

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.

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I just bought a 2004 RMZ250 and was working out wonky jetting. Mine started by being really cold blooded. Needed to stay on choke for a long time and basically ran like crap on the bottom end. When I bought it, it had 40p 3turns 185m. From the pilot circuit testing I knew that it was lean on pilot and from weird running that I was rich on main. Anyway, where I've settled jetting wise (sea level, cool 60's - 80's) is 42p, 2 turns, 4th clip (from top), 180m. I've got stock everything.

Gut feel, I think you're way rich pilot and rich on main. I'd start with 42p or like william said 45p 182/185m and retest pilot circuit. Pilot circuit is so so important in jetting. If you're getting a lean bog off idle, then raise needle some more. Let us know how it works out.

Mine runs really good accross the board now FWIW

Edited by erniek

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Also, remember to verify that AP squirt is working and not hitting the slide. When you have the carb off and with some fuel still in the bowl, crack the throttle to WO and see that squirt is functioning correctly.

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I have a 2005 rmz 250 with a fmf power bomb and powercore 4 slip on. i have been fighting this jetting for three weeks. i finnaly have it where it will idle and not pop and sputter. one thing that has really stumped me is it idles extrely high but when i pull the hot start in it slows the idle down and idles almost perfect. any solutions to this problem?

pilot jet-50

main jet-190

needle-4th clip down

air/fuel screw - 1.25 turns out

idle screw is at lowest possible setting

Your symptom is that of a 'too rich' pilot circuit.

I'd use a 45 pilot and a 182 main, and check you apump adjustment and squirt.

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thank yall for all the help i found out what the problem was. the throttle cable was frayed inside. now the bike runs perfect i found out by undoing the cables and setting the idle high and adjusting from there. i will probably keep the pilot the same for the simple reason that it was runnin extremely good this weekend at the AX probably will go down in the main though it feels almost like im pulling a trailer.

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