Trying to make sure I understand the function of the hammer fly. I have a problem where occasionally the hammer will not set in the fully cocked position. Half cock is no problem

If I am thinking right,
The hammer rotates back and engages the sear as normal, the hammer fly is moved by the rear trigger, but really does not have anything to do with initially holding the hammer in cocked position.

If I can't correct the problem with set screw adjustment, is it likely a sear/hammer issue?

Or am I missing something else?

That's possible.

It's not in front of me now. 
The front trigger spring mounts behind the rear trigger and runs along the edge of tang, resting on top of the front trigger, if I am picturing it correctly in my mind. Is that correct?

Thanks Bob.

The problem might be the sear spring. Broken, bent and or out of position.

I think it might be off the sear and resting on the trigger? 
The tip of the spring is in the notch of the sear that I think the trigger end comes up through.

Should have taken a picture, or waited until I had it in front of me.

Thanks, should have an answer in a couple hours.

Not certain of exactly what happened. 
Had problems with the hammer engaging the sear at full cock, pulled the stock to check and noticed the sear spring had slipped all the way to the side and the mechanism was pretty dirty.

Pulled it out to clean/lube it and it was same or worse than before.

Pulled it back out tonight and double checked, re installed, works fine. Tried over tightening the front screw that passes through and no change. Swapped the rear short screws In case I had inadvertently got them in the wrong holes the first time, and could not repeat the failure.

I’m sure it was operator error, but not sure exactly what happened. One of the short screws did appear to be polished or shiny on the tip so it’s is possible that I did switch the screws and or over tighten that screw.

Thanks for the help.

To adjust your set trigger put the rifle in half cock and then set the front. Back off the adjustment screw a wee bit and now screw it back in until you can see the front trigger now starting to move back. Then fine adjust it from there and typically you would want to back it out about 1/8 of a turn after it will no longer set. Hope that makes since and that would be the lightest point to where it could still be safely set. It does no harm to set the front trigger, and to dry fire it multiple times when doing this type of adjustment. Just make sure it is in half cock first or it might not want set at all and that is what I also have to do with my own.

You are probably correct the front set trigger is not actually made to work in pounds but to work in ounces and how it was designed to be used. You can use it unset but it is also god awful to try and use. I was having trouble with my mine at one point in time with the hammer getting caught at half cock when being fired. The fix was actually quite easy I added another flat sear spring on top of the one already there and that problem was solved. It also did not add any more pull weight to the trigger the one sear spring was just not strong enough on its own. As I also added more hammer spring tension so I then had to add more sear spring pressure to also compensate for it. Also when cleaning just use lighter fluid as it also lubricates and will not attract and fouling or othe unwanted debris so its best to not use anything else as a lubricant and it also not nessecary to do so if being concerned about any possible premature wear.

In regards to there not being allot of adjustment this also holds true. When adjusting the front trigger basically all it is doing is taking all of the free play out of the front trigger its self and also adjusting the amount of the actual sear engagement so there is really not all that much to play with. The more sear engagement you have actually adds just a wee bit more distance to the amount the trigger has to move back before it actually fully releases the sear engagement. You also don't want to have any remaining free play when you get to that point and again the amount of the actual adjustment is really not very much. 
Might also add the adjustment screw should not bottom out before it can be adjusted to the point of the front trigger not wanting to set at all and if so it just needs a little longer screw.