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 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.