Dave:

I am having a similar problem with my 110. I previously had an air leak around the airbox but at your's and Richard's suggestion, I replaced the airbox gasket. The method of replacement as Richard suggested should allow the airbox to be tightened evenly without the airbox cover hitting the carb. Richard suggested that the pressure from the carb causes the airbox bolts to be tightened unevenly.

So, I loosened the head then tightened the airbox bolts with a tourque wrench (about 13-14lbs. lowest touque settiong on wrench) to be sure the bolts were evenly tightened then tightened the head assembly back down and the engine ran great for about 10-12 flights.

It seems that a new and perhaps unrelated air leak is occurring where fuel is leaking out of the carb and also air is leaking out of the carb. I tested this by disassembling the plane and removing the motor as I first suspected that there was a tank leak and I used an air pump and removed the lines from the engine and at this time I determined that there was no leak in the fuel tank or other plumbing. I then replaced the engine with the fuel lines connected and pressurized the tank system to about 9lbs and traced the leak to the carb. When I advanced the throttle the air all shot right out of the carb. I tested this against a known good YS enbgine and tank setup and the good setup did not lose any air when the throttle was advanced.

Is the regulater the problem or could it be the throttle barrel seal?

This is a 110 that I bought new off of ebay but, the previous owner had had the motor for a couple of years that never got used on his planned project.