Hello, this is Jim from Grand Rapids, Michigan, USA and this is my first post. I'm an avid Coleman stove and lantern collector, and happened upon a used 123 that I couldn't pass up. This stove is new territory for me. I dis-assembled the stove and cleaned everything up, except for the NRV on the fuel cap. I also made a new fuel cap gasket out of Viton. The stove fired right up after a proper preheat, but even after 10 minutes of burning there's a noticeable pulse to the flame, in addition to yellow flame tips (this is with a pot of water on the stove, with the stove resting on a block of wood). I realize that these stoves operate under much less fount pressure than a pump-pressurized Coleman, but there doesn't seem to be much pressure when I unscrew the fuel cap. I'm a novice when it comes to these stoves, but my gut tells me that I have a leak somewhere. As I'm writing this I thought that I should do a dunk test in the sink to look for leaks, however, what do you guys think? Also, I read the tutorial on the dis-assembly of these stoves. What size Allen, or hex wrench do I need to remove the pip assembly from the fuel cap?