Low End Carb Sputter

[Enmerdeur]

To be honest, I shouldn't have to work this hard to get this bike to run good. I can understand a bike that's 10 years old and sat around, but right from the factory, this bike should purr. I have a KTM 200 & 250 both 2009's and these bike's ran perfect out of the box and still do. I've heard some 300's can be a little finicky and I evidently have one, so lean or rich doesn't matter. I just want the bike to run smooth all the way through the throttle. I'm not a guy who is on the pipe all the time, I like to just chug through the trails.
I do appreciate all the input.

Dang that is just bizarre. That was one of the things that impressed me about the Beta 300 is it just ran great right from the get go and the jetting chart was spot on. All my KTM 2 strokes, not so much.

I know your year has the higher compression head and I believe the race ignition compared to my 2014. I wonder if that has anything to do with it?

[BETAGAR]

Well my 300 is back at the dealer. We're finding you have to jet super lean in order for the bike to run better but it still sputters 1/8 to 1/4 throttle and even seams to back fire a little. The ignition system is fine, so it's not that. I've tried different ratio premix, still no change. I have swapped carbs from another bike that runs great, still no change. The spark plug checks out black and wet, even with lean jetting. Could there be something with the head or engine cases?

[GMP]

Have you checked the reeds ? Bad reeds will cause a rich off idle condition. Also, are you sure it's fuel? Does it smoke a lot and Is your gear oil level dropping or consistent?

[BETAGAR]

Reeds are good, oil gets changed after every race and it looks fine. I don't notice excessive smoke. I have a KTM 250 with a lot of the same engine parts, so I was able to swap out for testing purposes. Nothing has made a difference. I'm running out of things to try.

[GMP]

I'm stumped as well. Mine is so easy even with different needles. GGs that were tough could be explained by the old cyl mold and crappy port tolerances, but this is a brand new motor and tooling.

What about the stator, did you try that? Measure the windings at least. Low RPM power to CDI inadequate might explain it.

[ricoyam]

Did the crankcase ever get pressure checked?

[BETAGAR]

Thanks for the suggestions, I'll mention these to my dealer.

[GMP]

Betagar,
Hope the dealer can get the bike sorted out. The 2K-4 Kokusan stator should also swap from an estart KTM. After that not much else. One thing not sure if over looked is the exhaust, check for an obstruction. Not much else left. Do you race ECEA harescrambles? I got moved up to A so I've been riding Sportsmen on the first line and noticed a few new Betas on my old BSSR line behind me. If so look me up at the national next month.

[BETAGAR]

Yes, one of those guys is me. I'll look for you next race.

[ktm526]

Did you find a solution BetaGear? Mine does the same thing. If I jet it lean it runs great. Definitely not a solution! Stock settings I have the same sputter you have described.