NO to the reg. My bet is the htr has a low fuel/oxygen level. Its complicated to explain, easy to show. Im just down the raod and would be happy to make the adjustments.
Here it goes. Where the 2 holes are in the 6″ neck tube is where the O mixes with the prop. There is a small jet which regulaes fuel, if you look in the holes you can see it from the side. It will look like a 1/4″ nut. trust me, its got a hole in the center (which can become clogged at times). any way you will need to remove the thermocouple (if you still use it, i dont) its the 1/8″ copper tube that always breaks.
Ultimatley you will have to retract the jet, by unscrewing, the jet/thermo valve from the neck. this will allow more oxygen to mix with the fuel and solve the onion eye problem.
I would start by backing it out 1 rotation and check it there. Keep in mind to tighten the jam nut and re attach the thermocouple.
It really is easy, its just hard to explain without using specific terms. If you have problems give me a call, i will be that way tonight and this weekend and would be happy to show ya, takes 5min. -Mark 612-227-6306