Hoping someone will help with my carb settings. Thought I had been running a 167.5 main, but realized I had a 170 in there when I went to change it. Just in case anyone remembered me saying the lower jet for a while.

1600 with Poorman's BAK, Baron's ported intake, pumpless w/Grizzly valve and a vented cap, plus a 1700 cdi. Factory Pro Stage One kit with Mikuni jets. Been running 37.5/170 at 3x out for about a year, with my needle on the 4th groove. Bike runs awesome at all throttle ranges. Bought a Baron's BAK on Ebay and was going to increase my main jet.

Got the carb on the bench, only to realize I already had a 170 in there, so I put it all back together and installed the new intake. My crankcase is vented to the ground, so I just put electrical tape over the hose connector on the back in order to see how everything worked out.

Bike idles fine, and runs great from about 1/4 throttle up to WOT. When I'm at just off idle, up through about 1/4 throttle, it sputters and jerks pretty badly. The problem seemed to lessen but not disappear as the bike warmed up. Pulling the enrichener out reduces the problem dramatically, and pretty much eliminates the problem when fully warm.

Suggests to me that I need to drop the clip on the needle one more groove. Am I reading that feedback correctly? Thanks for any suggestions!

Check your AIS nipple ontop of the intake manifold if its not soldered the cover will breakdown and crack. Sounds like an issue I had a while back.

Bullstang360 wrote:
Check your AIS nipple ontop of the intake manifold if its not soldered the cover will breakdown and crack. Sounds like an issue I had a while back.

I have the tube that went to the AIS on there still. It's plugged up and clamped, so it's not leaking and the tube is still in good condition.

The jetting should still be dead on and kicking ass. Mine runs balls out awesome on that jetting (checked it today, and still awesome!) Did you possibly lose the little O ring for the accelerator pump port when you pulled the bowl off? Do you know your float height?

Bet you haven't warmed it up good then adjusted the PMS have you? BTW you can plug the crankcase vent hole in the back with JB Weld.

Don't know the float height. I just used the picture someone links on here, showing the line the float should follow when eyeballing it.

I was pretty careful when removing everything, but there's no guarantee I didn't jar the o-ring loose. Guess I'll have to Google it unless you have access to a picture. Will try swapping back to the old intake just to see what impact that has too.

This sucks. I thought the jetting would be good as is.

Curt wrote:
Bet you haven't warmed it up good then adjusted the PMS have you? BTW you can plug the crankcase vent hole in the back with JB Weld.

Didn't mess with the PMS. Figured 3x would still be good. It's definitely seems lean where it stutters. Figured more turns out would be me trying to compensate for something else wrong.

Before you start messing with anything else, try moving the clip on the needle up one notch. So if it's on 4th groove down from the blunt end now, move it to the 5th. You might be surprised by the improved throttle response too.

Every time I've encountered the mid-range throttle sputter, moving the clip to a higher number has fixed it. I may not have memorized what carb settings to run with which bike setup, but I can say with little doubt that there are few here who have had more experience experimenting with different setups on the stock Mikuni carb. Besides, it's a hell of a lot easier to change the clip than it is to start chasing leaks and messing with float levels. At the very least if it doesn't fix the problem, it narrows down the list. And all things being equal, if the only thing you changed is the BAK, then nothing else should be different.

Doc_V wrote:
all things being equal, if the only thing you changed is the BAK, then nothing else should be different.

My sentiments exactly, which is what led me to suspect the needle. I'm really methodical when messing with my carb since I'm a novice. I feel pretty confident I didn't bend, jam, or lose anything. Didn't even touch anything really. Opened it up and the 170 was looking me in the face.

BAK is giving you more air than your old jerry rig filter. Adjust your PMS properly and do you have baffles in your pipes? You haven't said what pipes you have.