I have on that will idle but not reach maximum rpm. I have de carboned it and cleaned all gas lines. When it is idling should both cylinders be firing or is it progressive. It is a 70 something model don't know off the top of my head. Was running fine and all of the sudden one day can't get over an idle. Also burning excessive fuel. I took plugs out and changed. The bottom on is firing I check that. I am stumped as to what it could be. Any advice or input would be greatly appreciated.

Both plugs should be firing at all times. Do you have one cyl not getting fire at idle? (Running on one cylinder). Are both plugs showing to be running rich or just one?

Yes one cylinder not getting fire at idle. Plug is sparking and jets are putting fuel out. Compression test? Should that be next.

I will check plugs this evening and get back to you.

If one cylinder aint gettin fire no need to do a compression test. But more than likely a new coil. Swap the plug wires and see if it changes anything. If the cyl with no spark moves then you need a coil

Put new spark plugs in it. You say its a 70 somethin. In 77 they changed to the cdi ignition but i doubt its powerpack

Never mind about changin plugs. You said you did that. Do what i said with the coils and let me know