[chiphead]

Wow, the stubstack. Haven't heard that in many years. I'm sure it would have some influence, as this combo seems to be very sensitive to aircleaner/airfilter shape.

To be clear in my earlier post, the WOT AFRs were previously in the high 10s with the typical pointed type lid that gave 3/4" of vent clearance with a 3.5" filter.

With the dome only, the WOT AFRs were in the mid 11s. That's with 1.75" of vent clearance with same 3.5" filter. The dome adds about 1 inch.

With the domed lid, curved bottom and 4" filter I had 2.25" between the carb vents and the lid. Now the WOT AFRs are in the 12s. This is with the carb set up the old school way, with .027 HSAB and 2 emulsions, fuel just showing on the sight glass. This setup makes it slow to pull over, which is what I needed with the older aircleaner setup. Now with this new air filter, its too slow to start the mains (RPM at pullover is higher) and it's showing leaner on the highway.

Just going into detail, to show the minimum vent clearance rule of 3/4"has some caveats.