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pilot jetting help please, wr250f

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hello all, im trying to get my 2001 wr250f jetted just right...

the bike: 01, 269 cc big bore, hot cams, fmf pipe not sure which one....

current jetting: 50 pilot, red jd needle at 4th position, mj @ 175

bike runs ok, but here are the symptoms/ issues i dont like...

starts good without choke, little bit of decel popping, little bit of bog when rolling throttle on, so i will start the bike, i set the pilot screw per the sticky instructions which is at 1.5 turns

so i start it let it run and warm up and ride it around theneighborhood, however sometimes with clutch in and in first gear just coasting it will die, but it has a brand new clutch and i set it to factory play and movement specs

now after it stalls in the middle of the neighborhood it is super hard to start again, with hot start on....

any help would be awesome...

i tried going down a size smaller on pilot jet (48) and bike wont start at all with or without choke on...

everything on TT ive read indicates ppl usually jet leaner after a big bore install, could i be soooo rich as to cause these issues?

settings:so cal, 100' elevation, 65-70 degrees...


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When was the last time you had your valves checked? Everyone on here seems to think if your bike is hard to start, its the valves!! lol My 250x, it had the same issue, but it was actually a weak battery..

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Do a search for the correct way to set up your idle/pilot cicuit properly. Try the one posted up by William1. A 50# PJ does sound kind of "fat".

If this doesn't cure your issue, check the hotstart assembly. It may not be seating properly.

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Bike should always need the choke to start 'cold'. Pilot on your bike probably should be a 42 I'd wager.

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.

You will need to inspect and check the operation of the ACV (Automatic Coast Valve) BEFORE you mess with the pilot and fuel screw.

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