Carb tuning gone wrong.

The Mikuni or the mixes XS carbs I had on there would have the same effect of revving out, and I’m just not understanding something. I try to get the highest idle, but there’s a point where it just jumps up to 4500 rpms.

Everything I’ve looked up, this shouldn’t happen. Now, everything is driving fine from 1/4 throttle to wide open, she runs beautiful, but something just can’t be right with the idle circuit. I can get it to idle, but a quick snap and the engine just seems like it misses and one time it died in the road.
I do not have the Mikuni carbs anymore on the bike, but speaking carbs in general here as far as tuning, am I running to lean? Because it smells rich, and if I richen the mix, it takes off, if I lean it out I can get the idle to settle down.

In my way of thinking, I add more fuel it takes off, if I allow more air and reduce fuel it will steady at a proper range but it doesn’t make me feel good knowing it isn’t a smooth throttle response and half the time it dies unless I’m slow on it.

Here’s the kicker, if I use choke, it dies. I don’t get it. And I should also mention, I can start the bike without choke in 1 kick. Temps here are anywhere from 60 at night to 80 during the day, and don’t seem to have an effect.

Please help!

Wild guess here, if you can cold start without choke you're rich.
Go down one size on your pilot jets.
On idle to 1/4 throttle you are mainly on the pilot and air mixture Spectrum.
If you open the throttle and it dies...you might be rich Higher-up also( needle Heights/mainjets)
Ahhh the dark arts of carb tuning.
I've been refining the tune on my TM-38-85 flatslides for weeks now...not on my xs400 of course but on my xv1100

You should commit to one set of carbs. Most of us know about the stock carbs. If youre having trouble with a high idle on both carbs, try looking at other parts of the bike. I know nothing of aftermarket carbs.

I had high idle problems because i wanted my throttle cable tight and precise. This caused the cable to bind up and stick so it would never fully return. Try disconnecting the cable.

I would get the bike in tune, then the cable would eventually return and give me a a lot of problems that i blamed on the carbs.

Throttle cable wasn’t connected, I actually jumped up a jet size, and it’s more responsive. I don’t run both carbs, I’m using the mikesxs ones. Idle liked to hang or I couldn’t get the bike started while warm with the other lower to.

I actually started writing down all the changes I made and what the effect was. I’ve got an air screw instead of a fuel screw, so it was messing with me a bit. It runs better with the 40 jet, fine tuned the mixture screw, but it’s still not quite right, slightly off. I think I need the other pilot jet size up yet.

I don’t understand why it races like it does, but it always either races or dies depending on the mixture screw direction you went. As far as I know it isn’t supposed to to that. But I guess I’ll jist have to keep trying different things. It is fully rideable with how I have it set now, but the idle is around 1200 or 1500 or so, my rpm gauge is off, idk.

This is what I’m thinking, it’s running on the lean part of the spectrum so when I get it more fuel, with open slides it has that cut-out in the slide, which is giving it X amount of air at idle, and the idle return was slow to return. So I’m thinking i have it more fuel so it starts racing. So I’m thinking I need a bigger pilot to match the air so that instead of it increasing rpms, it bogs down.

It actually backfired through the carb once and popped it off, I’ve since tightened it more and then I put that size 40 in it. But it did that when I snapped the throttle and it died. Spark plug was black from when I richened it on the mikunis, and now starting to turn white on the arc portion of the plug, so I’m assuming it’s running lean. It does return to idle better with the larger jet, and now I can start the bike no problems when warm. Easy startup when cold too but gotta let it warm up and then it runs and idles well. Starting to feel like a normal reliable bike, haha

Y’all weren’t kidding when saying it’s all trial and error. Different engines with diff intakes and exhausts, in diff areas and climates all need different jetting. Carbs are finicky.