Vstar 1100 (2004) - Lean issues

Hi everyone - I'm new to posting, but have been using the forums for all sorts of useful information for a while now. I have a 2004 V Star 1100 with slip-on exhaust that is giving me fits after I attempted to install a POD kit. The previous owner had a Kuryakyn air cleaner installed (skull design) where the plastic was cracking and falling apart, so I decided to just go the POD route instead, rather than replacing that with something else. The install was pretty straight-forward - I used a kit from the guy that hosts the facebook Vstar group, however I have not been able to get it running right since - it is showing lean at idle. Turning the PMS screws all the way in just makes it run better and increases the RPM, and unscrewing them reduces the RPM/Idle, which you can adjust back up with the idle screw, but backing it almost all the way out still shows lean symptoms. My understanding is that turning the PMS screw all the way in should kill the engine, as it would shut off all fuel flow to the carbs without the choke, but mine is not seeing this. This PMS screw response was seen whether operating both cylinders or pulling (and grounding) the plug boot on either cylinder.

I bought the extended Mikuni PMS screws that the Wiki mentions, so I know they are only supposed to be turned out about half of what the regular ones use, but, again, it doesn't seem to matter how far I turn them out - I'm still running lean. Specifically, at low throttle (before 1/2) the engine is extremely sluggish, surging, and there is popping and occasional backfiring in that range. Once I get past 1/2 throttle, everything starts to smooth out and the power difference is amazing, compared to what I had before. Applying a little choke seems to smooth out the lower end throttle response.

Carbs are perfectly balanced, but the vacuum level is low (around 150 mm/hg at 1000rpm) compared to the range indicated in the wiki (260-280). I had low compression on one of the cylinders, but that returned after readjusting the valves. I have replaced the intake boots and do not see an indication of any intake/exhaust leaking. Spraying starting fluid around the intake ports to the engine does not do anything. Spraying it around the carb intakes can sometimes see a response, but it is not consistent and I think it is overspray getting into the pod filters, since they are so close by. The carb intake/filter boots are in great shape, with no cracking evident.

The POD kit only changed the main jets (147.5) and added a washer to the needles. While in the Carb, I realized the seals and slide diaphragms could stand to be replaced, so I bought the Mikuni rebuild kit and went ahead and changed everything out, cleaned ports, etc. I also verified the float heights are good, per the Wiki recommendations. After experiencing the issue, I checked the pilot jet and found that the previous owner had changed it to 25, which seemed very high (17.5 or 20 are recommended). For sh--s and grins I popped a 20 in there, but it had no effect, so I went back to the 25.

I also did some research on the Kuryakn cleaner and found that the install instructions include a change to the air bleed port within the top slide chamber. I could not find any information about that port online, and I'm not sure if the kit made it bigger or smaller vs. stock. I have the stock ones coming from partzilla, just to eliminate that variable.

One interesting thing I saw last night when I was verifying the sync levels - I added a little choke to it. The RPM's went up, as expected, but the vacuum levels were what was weird - on the front cylinder, the vacuum levels rose significantly, but the rear cylinder maintained the same vacuum level. What would cause that?

Several people have indicated that I have an air leak somewhere, which is why I did all the other investigative work above, but I don't see any evidence of a leak anywhere. The fact that turning the PMS screws in doesn't kill the engine makes we wonder if there is an issue on the air cut-off circuit (that diaphragm was replaced and everything cleaned when I used the rebuild kit) or the choke/throttle advance (also serviced with the rebuild kit). Would an issue with either of those on just one carb (i.e. rear cylinder that did not increase vacuum under choke) create the same issue for both carbs, such that with only one cylinder running (either one), the PMS screw being all the way in would not kill the engine?

I've been at this for weeks (in between waiting for new parts to come in), and while it seems to be better than it originally was, it is nowhere near where it should be in the lower end throttle.

Sorry for the extremely long post, but I wanted to make sure I put as much information in here as I could, as you never know what might be relevant.