Jet recommendations for Honda 250sx??? Anyone?

[S250X]

Hi, I just recently purchased the 250sx I had when I was a kid. It is in definite need of a carb rebuild, and I want to rejet it at the same time. I know jetting is kind of a trial and error process, but I don't even know what size to jump to. How much difference does one or two sizes make. It has a cobra pipe now, and I want to put in a k & N filter and remove the airbox lid. It currently has a 128 main jet and a 38 pilot jet in it now. So basically how many steps up of each should I order? I am going to order thru jetsrus.

[Dirtcrasher]

I don't care for the K and N unless you run an "outerwares", I just run UNI......

When I popped on a 350X carb with similar mods (although I have a cam and 11:1 Rocky piston) I jumped up to a 138 main and a 42 pilot.

Unfortunately, you have to buy a bunch of jets and start with a big main and see what it can swallow. Bump up that pilot too or the headpipe gets super hot......

That cobra pipe really breathes so you will definitely be jumping a few sizes.

[S250X]

Yeah, I may just run a uni also. That seems to be what most guys are running. Well, I shouldn't have to go any bigger than you did then. Because I am not planning to do a cam swap or anything. Yeah, it is a bummer that you have to buy an assortment of them, cuz they aren't cheap. Did you buy the genuine Keihin ones or the aftermarkets? Seems like someone said that I shouldn't use the aftermarket ones because of the poor tolerances.

[Dirtcrasher]

Buy the genuine ones.....I don't even care for the EBAY knock off carbs myself. MRCycles was fairly inexpensive for jets, they have a "parts unlimited" catalog; I believe thats where I found them.

Otherwise, your dealer wants 5$ or more per jet and now that I have well over 200 jets, you can do the math :lol: It is well worth the money when you get it jetted to both start cold and pull through the whole throttle range.......

[S250X]

Ok! So I jumped to a 138 main jet, and a 42 pilot. I also installed a UNI filter and removed the air cleaner lid. The bike idles great and the top end power is excellent-great improvement. But the at the lower end it bogs annd hesitates a bit. Especially just of idle. If you gun it right off an idle, it doesn't do too well. Do you think my pilot jet is too big for what I am running? I have other jets, just not sure which way to go at this point.