SX performance - (I hijacked a thread instead of starting my own)

[nouseforaname90]

-wonders- I know the SX isn't meant for speed.. but a little more would be nice. Can you get an aftermarket reed cage for an 85 250SX? How about jetting/carb kits?

[Red Rider]

Can you get an aftermarket reed cage for an 85 250SX?
Those are more rare than Calfab swingarms! ;)

[hrc85250r]

haha, sorry nouse, four strokes dont normally have reed valves...

[nouseforaname90]

-shrugs- Oops. Can't ya tell I'm new to this? lol. You learn somethin new everyday.
Well what about the carb jetting then..

[Red Rider]

Nouse, unless you've done some engine mods to your SX & haven't rejetted yet, then there's nouse in bothering with it. That being said, not all engine mods are going to require rejetting the carb to run properly. A lot of people on this forum talk about carburetor jetting like it's a performance mod, and it isn't. It is a modification that's done in response to changes that cause your air/fuel mixture to be incorrect. Some of the things that cause that to happen are:
1. Engine mods: Porting, exhaust, airbox, carburetor, reeds, ...etc.
2. Atmospheric changes: Temperature, altitude, ...etc.

[Dirtcrasher]

A cobra exhaust, 350X carb and removing the airbox lid give the SX some great gains. Then add a Web Cam, High Comp piston and performance valve springs like mine and you'll really notice some very nice gains.

[nouseforaname90]

Sorry about hijacking the thread.. lol.. I was just going to ask one question, but it kinda turned into more than one.
And where would I get the piston and valve springs? Websites?

[Tri-ZNate]

Sorry about hijacking the thread.. lol.. I was just going to ask one question, but it kinda turned into more than one.
And where would I get the piston and valve springs? Websites?

denniskirk.com i'm sure would have them. Webcamshafts.com has some awesome cams for any model. And just simply taking the air box cover off helps alot.

[straight pipe]

well i old schooled it. i cut the spark arrestor right off and i installed a k&n, i ride with my box lid on for water reasons. bought itp aluminum rims and mud lites for a lighter package and added traction.also installed a 200x front end which is also lighter i don't need to fool with jets cause it didn't need it and goes like stink. i raced a friend on a stock sx a few weeks ago and smoked him bad. he couldn't believe it. top end i don't think it is that much faster but the mid range is nuts.....really fun!
install the lites and the rims you won't believe what a difference it makes!!!

[bigredhead]

I bet 23.5 " tires would fit nicely vs the stock 22's.. an extra 1.5 inches in diameter should provide a few more mph without affecting takoff too much.

[straight pipe]

hey that would work good ! it definently has got the power to turn em!

[conig]

Dirt Crasher if you don;t mind me asking what jetting are you running with the 31mm carb? I have a 34 mm vm Mikuni I want to try on my big red. I would like some type of base line to tune off of.

[nouseforaname90]

If I got a 350X carb to put on my 250SX, how would I put it on? Would it just go on the same as the SX one, or would it be different?

[nouseforaname90]

Ok. Well I decided to try my SX without the airbox lid on, and I'm not sure if I like it or not. I think it definately lost some power, but it might have gained speed. I don't know if its my imagineation or not, but it seemed a little faster going in 4th and 5th. But the sound is so throaty now. Before it sounded regular.. like what you would hear on any ATV.. but now its.. idk.. a weird sound. Not bad, its louder than it was with the airbox lid on.. lol.. but its gained a new throaty sound. I dont know what it is.. would rejetting help?

[Yamahauler]

If you want to run without the airbox lid on, you will have to rejet.
Becareful riding it right now before rejetting, if the f/a mixture gets too lean, you'll overheat it and screw your top end.

Check to see what color the end of the spark plug is, if it is white, its too lean, you need a larger main jet.

[bigredhead]

When there is gain. there is loss..

more air will provide more power on the upper RPM's.. but will take away from bottom end RPM's. It's all about what you want and need.

It's an SX not an R.. put that lid back on and get muddin ! LOL..

[conig]

is there a general rule of thumb for the 250sx/es when removing the lid? like a one size larger main or two sizes larger main.

[nouseforaname90]

Thanks. Where could I get a jet kit for my SX? I couldn't find one by running a search on google..

[bigredhead]

your honda dealer can sell you individual jets.

check on denniskirk.com also.

[nouseforaname90]

Hmm.. well.. I like having more RPM's in the bottom end.. that gives me more power for acceleration and muddin. lol. I'll leave my lid on.

[straight pipe]

tell you what... after i did the mods that i listed i can can let her rip in third in deep mud and it doesn't bog down, tons more grunt.i'm tellin ya..a k&n and free up the exaust flow and also a good set of traction tires makes it pull harder in the mid range.