I am unable to get the petcock mounting screws out.  They are seized up and I have been unable to get them to turn.  Trying not to mess up the heads of the screws.  I'm using   I have a new petcock being shipped.  I've soaked them with kroil for several days.  I'm thinking of using a large soldering iron to heat them.  I'm leary of using a torch.  I removed rust from the tank with evaporust and it cleaned up nicely.

Any suggestions on getting these screws out?

 from near Salisbury, UK.

The screws are easily replaced, so I wouldn't worry about messing them up. I would use a pair of mole grips. If the screws snap, drill out to 5mm and re-tap a M6 thread. 

Thanks! I just got them out. Heated with a huge industrial soldering iron. Amazon dropped off some japanese bits.

used a dremel tool to slot the heads and used an impact driver.

New petcock and screws coming from Partzilla tomorrow.

I've had this bike since new in '75. Got it for my 14th 'm 64 now. I just pulled it out of storage.

I would not use a torch, even if you think you have it completely clean. A neighbor has a buddy that did a weld on a gas tank that he thought was completely free of gasoline, and it blew up on him. Apparently the fuel soaks into the seams, and is very hard to get completely out. The screw head is probably JIS, so may be slightly different than SAE number 2. I bought an inexpensive set of JIS bits, and I just tried it on my bike, and the JIS does fit the petcock screw much better than SAE number two.

www.amazon.com/dp/B0DKD9BFSN?ref=ppx_yo2..._fed_asin_title&th=1

Ah, we were posting at the same time. Glad you got them out!

Congratulations and welcome!

Greetings from Tennessee  

Great to hear you are on the way forward!