Take of two mowers

I have two sickle bar mowers that are given me different results in the field. Mowing grass hay.
I one field I used. New Holland 451 sickle bar mower. It is a rear mount with pitmanless head. 7 ft bar. In regular or heavy thick grass hay it cuts very nicely. But when I went to a field where the hay was thin and light the hay falls onto the bar and will not move off very well eventually clogging the mower and it will not cut anymore hay until I lift bar and clear. . When the hay got thick in another part of the field it was fine.
I got out my Farmall Super A with a mid mount pitman sickle bar mower. And it handled the light hay with no issues. However when it got to the thick grass it struggled and started to plug. I think the issue is the hold downs in the bar.
The bar on the new Holland is set with no tilt to it I think the Super A is the same. The skids I dr the bar on both is set to max height.
The new Holland is run at 540 RPM. The Super A just runs max Engine RPM in first gear to make it through.
I have a manual on both and have been looking through them but no Inform in them that I have seen so far.
I did try varying the speed on the new Holland mower( using hydrostatic transmission to vary ground speed). It seemed better going faster but it was still not mowing cleanly.
Thoughts?
Where to look?

Hows your sections and guards look

Mt,

I have a 6 foot, Ford 501 sickle bar mower. It works pretty well but has all of the standard sickle bar problems occasionally. I mount it on my Ford 2000 and run in third gear to help the grass fall off the back of the bar. It clogs occasionally, particularly on tall grass that has fallen over (do you call that lodged?) but I just stop and clear the clog and go on.

Good luck with your mower.

Tom in TN

The pitmanless mower does not vibrate like the pitman mower. The vibration causes or helps the cut material fall off of the cutterbar. Tipping the guards up will help, but results in longer or taller stubble.

Plugging in heavier hay can be due to condition (sharpness and adjustment) of the cutting components.

Are the guard ledger plates on the Super A mower good and the knife sections sharp? The Super A should be able to cut through most grass (that is standing) on level ground in 3rd. gear unless it is swamp grass or old dead undergrowth.

LOL yep pitman arm mowers the vibration helps with getting the material off the blade especially thin grass. The newer 451 does better in thick stuff but will plug up more in damp or thin material. I still use sickle bar mowers to mow hay.