2007 with all the usual mods, 125 main. Bike sat for awhile, but started right up when I took her out. BUT as soon as I give her the gas, it dies. Pulled carb, cleaned main jet, gas flow is fine, kouba needle 2.5 turns out... I am STUMPED! Can get her to rev to about 4000 then it's like a kill switch. Any help or suggestions will be greatly appreciated, as I'm about to park it on the tracks. Cheers!
- Lucky

 

I think I'd pull the diaphragm cover and see that the diaphragm is OK [no holes or tears], and check the slide / needle jet isn't hanging. If the spring isn't seated right in the cap, it can cause cut out at wide open throttle.

You say you cleaned the main jet. There are some more jets in there that may be plugged or restricted, although they should have problems at start and idle rather than WOT as you describe. Did you pull the needle jet holder? And if so, did the little collar below that come out too, and was it put back in small end first? Symptoms indicate to me problems are in the needle jet region.....needle, jets, diaphragm /slide assembly.

I've had to clean a carburetor three and four times before I finally got whatever hint of buildup prevented it from running right. I'm finding aerosol carb cleaners are useful for checking that a passage in open, but they aren't very good at cutting varnish. I'm finding a soak in a good fuel injection cleaner is cutting down on the number of times I need to remove the carburetor to get what I missed the last time. Chevron 65740 Techron Concentrate Plus Fuel System Cleaner is my standard soak chemical, although I think Gumout Regane works maybe equally as well.

Please keep us posted.