Jump to content
Sign in to follow this  

2009 KXF 250 jetting and suspension settings

Recommended Posts

There is some talk about what jetting is stock and what should I run and so on...

In this thread we can gather info about what stock settings are and what Team Green and MXA thinks are good settings.

Of course everyone who has some experience in this can chime in with settings that work even better:thumbsup:

The settings we discuss here are for stock engines and suspension.

Be sure to include your surrounding facts with your info, as in rider weight, type of riding, and temps and elevation and everything that can make a difference.

Here are MXA´s settings for the 2009 KXF 250:

Fork:

spring rate 0.44

Oil amount 306 cc

Comp 9 clicks out

Rebound 9 clicks out (11 stock)

Fork leg height 5 mm up

Shock:

Spring rate 5,4

Race sag 100 mm

High comp 1-1/4 turns out (2-1/4 stock)

Low comp 9 clicks out (12 stock)

Rebound 10 clicks out (12 stock)

Jetting:

Main 180 (182 stock)

Pilot 42 (40 stock)

Needle NHJT

Clip Fourth from top

Leak jet 55

Fuel screw 2 turns out

I have set up my bike to their specs, but haven´t ridden the bike yet because of the winter and closed tracks:thumbsdn:

I can provide my personal opinions in about a month from now, if there will ever be spring:cry:

Share this post


Link to post
Share on other sites

Im going to try and try some diffrent jetting this weekend i will all let you know how it goes

right now i have

178 main

42 pilot

55 leak

stock needle

I rode with this and was getting major pop on decel temps were around 50*F

Share this post


Link to post
Share on other sites

In colder weather many bikes seem to prefer the #45 pilot jet. This should make the bike respond better to fuel screw changes.

Share this post


Link to post
Share on other sites

Cold air=Dense air=more power typically if you match the fuel. Slightly richer when its cold out is definitely the way to go.

Share this post


Link to post
Share on other sites

Is it the higher the number you go on the main the richer you are? I just wanted to know because I am new to four strokes, but thought that backfiring and popping was a symptom of being too lean. If this was the case, wouldn't going from a 182 main to a 180 make it backfire and pop even more?

Share this post


Link to post
Share on other sites
Is it the higher the number you go on the main the richer you are? I just wanted to know because I am new to four strokes, but thought that backfiring and popping was a symptom of being too lean. If this was the case, wouldn't going from a 182 main to a 180 make it backfire and pop even more?

Yes, a higher number jet is always richer (also the leak jet, but it "leaks" fuel back to AP chamber thus creating a leaner mix for the engine).

The engines backfire at small throttle openings. The main jet has nothing to do with that.

It is the pilot jet circuit that is responsible.

Some people confuse high engine RPM with throttle opening, in that sense that the rev´s are high and the engine backfires.

But the fact is that it doesn´t backfire until you close the throttle, thereby creating a lean condition.

simply put: the engine does not draw gas through the main jet at closed and small throttle openings.

If you study this image for a while it all makes sense:

carb_jet_usage1.jpg

Share this post


Link to post
Share on other sites
Yes, a higher number jet is always richer (also the leak jet, but it "leaks" fuel back to AP chamber thus creating a leaner mix for the engine).

The engines backfire at small throttle openings. The main jet has nothing to do with that.

It is the pilot jet circuit that is responsible.

Some people confuse high engine RPM with throttle opening, in that sense that the rev´s are high and the engine backfires.

But the fact is that it doesn´t backfire until you close the throttle, thereby creating a lean condition.

simply put: the engine does not draw gas through the main jet at closed and small throttle openings.

If you study this image for a while it all makes sense:

carb_jet_usage1.jpg

I'm starting to understand the difference between the main and pilot jet. I know you gave the specs saying that a 180 main would be better than the stock 182, but do you think that it would lean it out to the point where it is harmful to the engine? Also are these jetting suggestions from Cali, because then they would not apply to anywhere else except for Cali, right? I plan on trying them anyways and seeing how it runs and what the plug looks like, but I would still like the input for me being a newbie to this

Share this post


Link to post
Share on other sites
I'm starting to understand the difference between the main and pilot jet. I know you gave the specs saying that a 180 main would be better than the stock 182, but do you think that it would lean it out to the point where it is harmful to the engine? Also are these jetting suggestions from Cali, because then they would not apply to anywhere else except for Cali, right? I plan on trying them anyways and seeing how it runs and what the plug looks like, but I would still like the input for me being a newbie to this

A 180 is not really to be considered "lean".

The bike would hit harder and run "crisper" with a 170 main jet. If we are talking about summer temps.

180 is the standard main jet on european bikes.

Basically it runs better if it is lean, but not so lean that it bogs or overheats.

A too lean of an engine will run hot. It can even melt pistons and overheat the valves, not good.

So 180 is on the safe side for all temps basically.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×