Trackside jet changes on 05 KX250

[jchek779]

Hey Guys,

 

I'm wondering if I'm missing something here - I have an 05 KX250. Is there an easier way to get to the bottom of the carb to make main/pilot jet changes without having to remove the subframe/remove the carb?  I'm used to loosening the carb boot clamps and rotating the carb but the throttle cable hits the upper engine mount.

I hate having to pull the subframe at the track because I'm worried about dirt getting into the carb when pulling boots/pulling the carb out.

Any tips or tricks would be appreciated.

[Kx100TrailBoy]

Usually the boots will let the carb flex with the throttle cable but in this case, I'd try to find a new way to mount the cable.

[Jeekinz]

That's the easiest way.  Thankfully the CDI isn't in the airbox like the L Models had and there's only 3 bolts.

[SAPPERS]

This makes me wonder.....Are you trying to change jets at a race? or just tuning? How modded out is this motor?

 

Once I jetted ours, I never had to touch it again. Since it has the TPS built in, it helps alot. Whether it's 40* or 90*, the bike runs excellent. It even has an aftermarket head with a smaller dome and CR is pretty high. I run 50/50, 93/VP110.

 

These 250's are great. Once dialed in, they are pretty much set for life.

[jchek779]

This makes me wonder.....Are you trying to change jets at a race? or just tuning? How modded out is this motor?

 

Once I jetted ours, I never had to touch it again. Since it has the TPS built in, it helps alot. Whether it's 40* or 90*, the bike runs excellent. It even has an aftermarket head with a smaller dome and CR is pretty high. I run 50/50, 93/VP110.

 

These 250's are great. Once dialed in, they are pretty much set for life.

I'm trying to get the bike dialed in at this point.  I bought the bike used and it had a 45 pilot in it - it wasn't even on the taper of the air screw. So I'm in the process of going down on the pilot.  Then I'll work on the needle position and finally the MJ.  I don't mind having to yank the subframe at home and work on the jetting with test runs up/down the street. The issue is that I'm at a little bit of elevation (~2100ft) and most of the tracks I head to are not.  I'd just like to be able to fine tune things at the track if need be.

Riding Honda 4t's for 10 hears has seemed to spoil me because of the easy access to the underside of the carb.

[Jeekinz]

I ran 160/45 clip in 2 pos, stock needle. 

[SAPPERS]

Ohhh, I see now. OK, cool.

 

Nowthen. I think my jets are same as Jeekinz but my clip is 3rd pos. I can't remember, it's been awhile.

 

But your pilot should be the worst to deal with. But once you get that on, you shouldn't have to change it unless you're coming down to about 1,000' asl or up to 4,000. The main is where you're gonna have to make changes and they aren't too bad. You just need to find that 6mm socket setup that works for you. I use an old Craftsman igntion wrench that i bent in all kinds of weird angles to work to break loose and tighten. Once loose, I use a 1/4"dr socket to thread out and in. 

BTW, if you have big meat stumps for fingers, this might be tricky for you.

[moose_338]

158/45 2nd pos. on stock needle.

 

Just on the rich side of perfect jetting and I've never had to change it, once it was dialed in.

 

And that's at or around 600Ft above sea level.

[Jeekinz]

158/45 2nd pos. on stock needle.

 

Just on the rich side of perfect jetting and I've never had to change it, once it was dialed in.

 

And that's at or around 600Ft above sea level.

 

I was back and fourth with the 158 and 160. At the time, I was riding a large sandy area, lots of wide open stuff so I ran the 160.  Trails and regular MX the 158 is good.

[tt81621]

Maybe I am messing something up but I remove the top of the carb, 2 allen bolts.  Take the slide out, rotate the carb.  No issues.  Have to take the tank and seat off,  10 minutes to rejet the KX

[Jeekinz]

Maybe I am messing something up but I remove the top of the carb, 2 allen bolts.  Take the slide out, rotate the carb.  No issues.  Have to take the tank and seat off,  10 minutes to rejet the KX

Now you have a gaping opening for dirt to get in.

[tt81621]

Stick my goggle rag in there.  It is the only trail side way I have found to change jets.  Way easier and less room for dirt to get in than taking the subframe off.