Jetting the 2-Stroke KFX50

[represent618]

With an airbox mod, removal of the exhaust and intake restrictors, the jetting is way off obviously, I have extra jets so i drilled a needle jet slightly bigger and removed that restrictive pilot jet and left the inner pilot jet which is the larger one and just played around to no avail.

Any one know exactly what jets to use?
Needle, Pilot, Main?

With the restrictors out and the box modded, you can hear the little bike just waiting to come to life

[represent618]

I ended up making an insert for the airbox lid out of a carb cleaner can cap and siliconed it in, sealing off the holes I drilled.

So now I am back to stock jetting and airbox with only the two restrictors removed and it runs good, a lot better than it did factory setup. But if anyone can share some experience on jetting I would appreciate

[hawaiianbasshed]

why not try one jet richer? with the airbox holes open? I can check mine some time that has the holes in it and the midwest mini power package and see what jet size it has. granted I haven't run it, I imagine it WAS running like that since I got it used with alleged clutch issues...

I did start it but for sure will pull it apart sometimes to clean out the pilot jet. so when I do, I'll post what size jet it has. mine does have holes in the airbox as well as a dual stage UNI type filter...

[hawaiianbasshed]

oh also mine is an 80 so... not sure if they have the same size jetting, I would think mine would be larger :(

[859davidt]

I went all the way down on the needle and #60 on the main. The only restrictor I found in mine was the core in the silencer. Didn't find anything in headpipe or intake.

[Hemi636]

We had an 03 Suzuki 50 which was the same as the 2stroke Kaw. This is what worked for me when we had ours:

-removed piggy back jet in carb

-had the head milled .020 to increase compression

-change to cooler plug NGK BP5HS (BP4HS is stock)

-replaced stock air filter with K&N style. My notes say it was a# RU-0200 This took cutting off some of the stock air cleaner / intake plastic. I cut it to leave me with an oval piece going into the carb, then I tightened up the air-cleaner to that oval section of plastic.

-replaced main jet with #65 (stock was #55 I think)

-moved carb needle to 2nd from top position - that worked best for us

-disconnected oil injection / ran pre-mix 32:1 -just removed the banjo fitting & replaced it with a bolt.

[techoca]

I am in the process of rejetting my kids KFX50 after removing the intake and exhaust restrictions. The unit is very lean; so far I have tried a .70mm main jet and it is still too lean. I will be trying a .80mm jet today. With it being so cold, I may have to go back to the .70mm in the summer.
My question for you KFX50 modders is this; do you run the units on the prime setting, thus allowing gravity to feed the carburetor or do you continue to use the vacuum pump? BTW, I use a 32:1 premix and an NGK BPR5HS spark plug.
Thanks