You guys helped me get gunning, now just need to fix this stutter at 4K RPM!

[JonathanPD812]

Hi guys! I got a 1978 Suzuki GS400. Ran great, stopped suddenly one day. Some history on that here:

https://www.thegsresources.com/_forum/showthread.php?261912-NEED-HELP-Starts-(sometimes)-but-dies-when-I-apply-throttle

Long story short you guys helped me go from dead to running! And 0-4 RPM is quick and sounds great. When I ride around and get past the 4-5k RPM range she PULLS which is great. Lots of power and runs like a dream!

If I could figure this issue out I'd be all set! I have no idea what it is but it's only from 4-5k. If I go slow on the thottke I can work through the stutter and I'm off!

Thoughts? THANKS

[ItsBork]

Hey sweet we have the same bike!

Have you done all the obvious stuff? Timing, spark plugs, check for air/vac leaks?
I see from your old post the carbs are freshly cleaned but have you checked the jets recently? It takes very little to clog them so even if the rest of the carb is spotless you could easily have knocked a piece of shmutz loose that ended up in the jet. Doesn't hurt to at least check the main jet if nothing else.

[JonathanPD812]

I did, I went through one of the senior members top 10 mistake lists and did all the normal maintenance things...

You know that's a good point. I actually had some rust in my tank I was cleaning that I didn't mention anywhere... Some of those bits may have ended up in my carb... Also until you said it I didn't realize that mid range is the main jet so I bet your spot on.

[Big T]

Mid range is the needle, then the main jet

[JonathanPD812]

Mid range is the needle, then the main jet

Okay! Do you agree then that it's likely more junk in the carb (blocking the needle)?