Mower deck belt tension - ?slipping

[510racer 0]

Finally got the 42" mower deck working on my 310-8 and have an issue.  When testing it out recently the blades would stop turning.  Seems the grass was high and maybe damp and/or the deck set too low and the discharge would clog.  I didn't change the spindle belt. 

Is the spring loaded pulley supposed to be free? i.e. able to slide during operation?  I noticed whoever before I owned had installed a extra jam bolt to hold the sliding bar..

Or do I just need a new belt?

Thanks!

 

[oldredrider 2,553]

The slide bar should be free to move. The spring keeps tension on the belt.

It should NOT be locked down or obstructed.

[groundhog47 347]

It may be stuck in place from debris build up. Some have steel washer top and steel bushing below bar. The steel one "freezes" up a bit easier. Some have a nylon/plastic washer/bushing replacing that set up. If you've not removed deck and checked spindle bearings, it would be a good thing to check and grease them and check the pulley grooves for overload of debris and a free turning idler pulley. 

[Jeff-C175 7,207]

Is the correct spring installed?  or has the old spring gone 'weak'?