Sunmaster Belly Mower.

Cosborn -

Are you using the old round belt or the new style double V belt? Or a regular V belt?

I had the same problem on my C with my 60" SunMastr, the old round one finally gave up the ghost so I bought a new double V Gates. It kept throwing it off, sometimes right away, sometimes it would take a few minutes of mowing. I kept putting it back on, tightening it a little more, over and over, until a light came on, I backed off the adjustment until the belt seemed like it was too loose. Haven't touched it since, works like a charm. I guess since it is a big belt and has a lot of surface contact, you don't need to run it too tight.
It has been a really good deck, I have many many hours mowing the "rough" outside my yard - thick and thin, tall and short grass, with the odd branch and rock thrown in. About4-5 acres. Plus I raise it up all the way and mow the tops off the grass in the pasture as our sheep won't eat the woody heads. Bought new blades last year and it mows as well as my $6000 zero turn.
cheers,
Creek

could be your pulleys are worn too

Any pictures of the deck? My label is damaged, may be a Sunmastr. Photos of your deck and label may help me identify it. Thanks!

Ill get pics tomorrow.

Here is my C with the Sunmastr deck. Belt guard removed, front wheels are not Sunmastr, I added them later.
Creek

Keep the spindle bearings grease - mine has a "weep" hole on the side opposite the zerk, I grease them until the ugly stuff stops coming out. If you can find a zerk on the center pulley setup let me know - I can't find one and it seems like that bearing would have a lot of side pull on it. You can still get parts from Artsway in Iowa if you need them. Spendy though. Blades I bought from a mower parts outfit - they are a little hard to find as they have two off center holes, no hole in the center of the blade. I've put a lot of hours on mine, it works pretty dang good.
cheers,
Creek

I have that exact deck on my 1943 Allis Chalmers B model.  Does anybody know where I can get the pulley's for this?  

I have a rusty old SunMastr deck behind the garage. Free to anyone coming to central Pa. Who can use it.

If you would cut the idler pulleys off the deck with a torch I would buy them from you if you shipped them. I could send you a check, paypal, etc.  You tell me how much you want for your time and labor.  I am desperate.  Do you have any pictures???? 

I don't know what your idler pulley is like, but idler pulleys in general are rather easy to find.

Creek  That is on NICE LOOKING C!!  Love those decals.