Scag walk behind mower belt drive slipping in reverse but not drive

[Swhite76]

I just bought a scag walk behind off facebook market place and its in REALLY good shape. Practically brand new. Only thing i have noticed is that it drives fine in gears 1-4 but keeps jumping out of 5th. Also when i put it in reverse it doesnt go anythere. The transmission spins but its kinda like there is a idler pully missing on the bottom. I dont know if i buy a idler pulley and put it on it if it would have it too tension or not. Is has a bolt in the position where one could go but asking opinions. I came to the conclusion that it doesnt have enough tension to engage the wheels to go backwards. Springs are strong and not the problem. The tentioner pulley does not put enough tension on the belts to go backwards and there is no adjustmens for it. Has anyone tried putting a idler pulley on the bottom to help with this specific issue? If so let me know how it worked.

 

[hlw49]

Trouble is when you go to reverse it changes the direction the belt turns. Since the idler is on the opposite side that would tighten the belt in this position they slip. You have to help it by pulling it backwards in reverse. I have never seen but one walk behind that would pull in reverse and that is the Snapper. They have a double idler setup that tightens the belt when you go in reverse.