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2007 kx250f jetting?

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How do you know? In what part of the throttle operation? What characteristics is exhibiting that appear lean to you?

 

You can richen a bike to the point it will not run, at worst your'll foull a plug. You can also lean a 4S out to where it will not run and not hurt anything

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well the bike runs great, its just my header turns red from the exhaust port about 6 inches out on the header. im not sure if thats normal or not. i used a temp gun on it and it was around 400 but im not sure if it was fully warmed up because i only rode it around the yard for about 5 minutes. not hard riding at all. im only worried about cracking my header. 

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Krannie, KX250F's love the 42. But his fuel screw is too far opened, probably in a misguided attempt to reduce decel popping.

 

OP, a glowing header is normal. Riding in the yard is not way to ride a race bike. Like driving a F1 car down the driveway to get the mail. 400 degrees is nothinh. It will hit over 1,500 at the exhuast port with you really get the bike going on the track, where it is designed to be ridden.

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i appreciate all of your input! i am new to the motocross world. ive only had a drz 125 stroke and a drz 110 before i decided to go bigger, cant blame a guy for wondering when you spend nearly 200 dollars on a header! William1, what would you recommend on my air/fuel screw?

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also when i get it cherry red, and im done riding, would you let it idle and cool down before shutting it off so it doesnt rapidly cool and then crack?

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i appreciate all of your input! i am new to the motocross world. ive only had a drz 125 stroke and a drz 110 before i decided to go bigger, cant blame a guy for wondering when you spend nearly 200 dollars on a header! William1, what would you recommend on my air/fuel screw?

 

 

also when i get it cherry red, and im done riding, would you let it idle and cool down before shutting it off so it doesnt rapidly cool and then crack?

No, never let the bike just sit there and idle unless you have to. It requires airflow through the radiators to cool it. Letting it sit and ridden slow ican cause it to over heat.

 

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 1,850 rpm, but go by the spec in your manual.

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It would be a good read for the OP if...... he had a 2S

This is truth. I knew I had it saved as a favorite and just went to it without remembering its geared toward 2t

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