Tune FZR 250

That depends - power output and therefore the amount of fuel required is proportional to the amount of air an engine consumes.

The standard setup is likely to run the mixture as lean as the engine will tolerate due to the requirement for minimal emissions and a competitive fuel consumption and it is probably this that is at least partly responsible for Hondas famously suffering a reduction of midrange power when exhaust backpressure is changed - pattern replacement exhaust silencers rarely deliver quite the midrange results of OE.
Honda development means the cam profiles and valve timing work in conjunction with exhaust design and carburettor settings and it is unwise to consider any one thing in isolation and there is more affecting carburetion than the main jet. Depending on carb type there is the needle profile, needle jet and possibly dashpot spring to consider and tuning a carb successfully to perfection is something that is almost a "black art".

Few minor modifications either increase the pressure on the engine pistons or succeed in making the engine consume more air and therefore it produces no more torque or power but where air consumption is increased, more fuel will be needed though all most kerbside rejetting achieves is usually a heavier consumption for little or no net gain.

I suggest you remove the baffles and ride the machine and if it isn't significantly better - put them back again, because for most people most of the time the manufacturer knows best and they spend millions making the best compromises. If you want something different from your bike - get a different bike!

Remove carburettor bowl and the pilot jet is just forward of the main jet and emulsion tube. If pilot jet is blocked either carb clean or strand of electrical wire will clear it then blow out with compressed air. Fuel mixture screw is just forward of float bowl. Start at 1& half turns out from seated.

Instructions

1

Fine tune your motorcycle before rejetting your carburetor. If it's still running too lean, you can replace the pilot jet as a first step
2

Remove the bowl at the base of the carburetor by unscrewing the screws holding it in place. Unscrew the pilot jet inside, but be careful not to strip it. The jet size will be on top.


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3

Use a screwdriver to remove the main jet from the brass jet needle holder, which is also called the emulsion tube.
4

Put in a pilot jet that is one size larger. Replacing it with a jet two sizes larger will make your mixture too rich.
5

Tune the slow/idle settings before replacing the main jet. Replace the main jet with one size larger. The sizes are in increments of 5.
6

Put the bowl back on, and align the accelerator pump shaft and rubber boot.
7

Reinstall the carburetor on the motorcycle and retune it to finish the rejet procedure.

change main jet in the carburettor install K&N air filter and iridium NGK or DENSO spark plugs tune up your engine change oil filter and oil. Flush your radiator check tyres pressure, Check engine compression and air leaks from inlet manifold ,Run hi octane fuel and injection cleaner mix for 250k to clean the carbon in the cylinders ,check for fuel hose loose ,carburettor leaks,distributor cup aluminium contacts to be clean, Vacuum hose on distributor unit for suction for advance timing .

Hi, you could remove the drain screw from the bottom of the float chamber, this is the lowest
Point on the carburettor, however if u are having running problems, the best thing to do would be to remove the carb-s
Remove and clean out the float chamber including the main jet pilot jet, and choke tube,

Hi and welcome to FixYa,

On a 2003 Kawasaki KLX125, these are standards:

• main jet - 145
• pilot jet - 17.5

Good luck and thank you for asking FixYa. Happy Holidays.

looks like your carburettor's giving out a rich fuel mix there or you've forgotten to turn off the choke get you carb tuned or jetted for better mileage (at a loss for speed - acceleration & power... if that's not important to you).,,