06 kx250f jetting help please

Ok guys im having trouble on a 06 kx250f with a brand new jardine rt-5 just installed right after engine rebuilt.I am running a 172 main 42 pilot 3rd clip from the top needle positon and fuel screw out 1.5 turns.Ok when i first start the bike it starts great and all that and when i first ride it it runs pretty good until it gets warmed up then it pops like crazy when on the gas right when i twist the throttle and keeps doing it even when i twist the throttle more.Also too the bike trys to kind of die on me at the point of when its popping like this after its warmed up.I had no problems on this bike at all untill i installed this exhaust.Im starting to get upset that my motor has 1hr and half and i cant ride it at all.It runs good and pulls hard until like i said it warms up.Someone please help me i cant figure out what to do or where to start.I have cleaned the carb completely twice now and new spark plug sealed the exhaust with high temp gasket sealer where the mid pipe and header meet cause i think it was letting air in a lil.If anyone has some suggestions please help i have never had the jetting this bad to whereit pops right off the slightest twist of the throttle,what should i try or do?If u know some tricks to do to count things out let me know thanks

the bike had a 170 main and 40 pilot and 3rd clid pos and 1 3/4 out on screw before i went to the 172 main 42 pilot settings as i got these from other people suggestions.Should i go back to completely stock or what was in my bike with my stock exhaust on it

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.

Check and ensure you have no exhaust leaks.

Keep in mind, you have a race bike and an open pipe. Nothing to muffle the pops. Your bike is designed for WOT then hard on the brakes, not coasting like a play bike.

good info but u think this will take care of the popping and hesitation on acceleration then i sure hope so,its got to be jetting problem correct being that it runs perfect until warmed up correct

No, re-read what I posted. It might reduce decel popping. You have a race bike, race bikes with open pipes are not meant for coasting.

If you are having misfires on acceleration, that something else. You posts are not succinctly clear.

Your bog the the AP.

How to eliminate the 'Bog'

No, re-read what I posted. It might reduce decel popping. You have a race bike, race bikes with open pipes are not meant for coasting.

If you are having misfires on acceleration, that something else. You posts are not succinctly clear.

Your bog the the AP.

How to eliminate the 'Bog'

oh ok well its popping/cutting out when i get on the gas i race and know how to ride a bike there is no coasting in mmy vocabulary lmfao.What could it be it runs fine before it warms up so therfore i thought it was jetting,its doing it so bad i can not even get a plug reading on my new plug.Everything is new on the top end and it has 1.4 hr on my hr meter.Also too this stuff did not happen when i had my stock exhaust on my bike then i blew a hole in my stock header so this is the reason i bought the jardine.Put it on with some recommended jets and this is what i have,i thought it was leaking air where the mid pipe and header come together cause there is no clamp there.So i put high temp gasket there and a hose clamp to seal that up there.what could be causing this to happen when my bike is warm then bro?Thanks

Go back to the stock jetting. You are too rich.

And please accept this as helpful criticism. You need to slow down when you write, read it a few time before you post.

Go back to the stock jetting. You are too rich.

And please accept this as helpful criticism. You need to slow down when you write, read it a few time before you post.

ok thanks and sorry,i kinda get in a hurry sometimes and dont make sense lol.I am gonna work on it today and try to get it right.Does moving the clip toward the bottom lean the carb/raise the needle and moving the clip toward the top richens/lowers the needle?

Once again, take more time, think things through. You have it backwards. Moving the clip towards the top/flat leans it.

Your jetting is close enough to run pretty well. You have another problem; perhaps a kinked or clogged fuel line, clogged fuel filter, float or needle valve issue. Something is wrong besides your jetting. Put your jetting back to where it ran before and find the problem. (IMHO of course).

Your jetting is close enough to run pretty well. You have another problem; perhaps a kinked or clogged fuel line, clogged fuel filter, float or needle valve issue. Something is wrong besides your jetting. Put your jetting back to where it ran before and find the problem. (IMHO of course).

thanks ya i came home yeaterday and tryed to start it it wouldnt start.Well i checked to see if i had spark and it looked weak when i did check it.So i started testing things and all that and when i took my coil stick apart where the harness comes into the stick,it was all caked with dirt.I took air and kleened it up real nice and put it all back together.Well what do ya know it fires right up and runs pretty good,i still need to fine tune it a bit,but it didnt cut out after it got warmed up this time.This was the first time it didnt cut out too so i was happy.I hope cleaning the coil stick up fixed the problem for good,if not its definately something electrical.Thanks for all the help guys and will let everyone know how its doing once i get it fine tuned.

Clean the connections with contact cleaner, put a dab of dielectric grease on the connections and reconnect. You'll be golden.

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