Sounds like you need to replace the belt. The only adjustment is to the bell crank on the deck which takes up cable stretch. The belt you need is Toro# 42-0884 and is about $6.89. You might be able to substitute a 1/2 x 24" cogged belt but since the savings is only a dollar or two, I'd recommend genuine Toro.

Is this something I can tackle myself?
You sound like you know the process. Would you be able to give me a few pointers on replacing the belt?
It would be appreciated.

Before replacing it, check under the plastic cover for the belt mechanism. Much of the time, it has grass,dirt,and other junk caked in there. If you clean it, the blade may start working better. Also, if you need a temporary solution, you can put belt dressing on the belt and it will work better for a little while.

I second the notion of replacing the belt w/ the oem. The repair itself is not difficult. Occasionally you will twist off the mounting bolt for the plastic cover on the bottom. Sometimes the small pulley gets replaced too. Remember to tip the mower with the airfilter up.

"...Remember to tip the mower with the airfilter up."

Is this so that the oil does not spill out??

That is so oil/ fuel doesn't contaminate the air filter. If you think you will have it on its side awhile- go ahead and drain the fuel and oil 1st.

Update.....

I was able to get the belt off last night. Not very difficult at all. 2 bolts for the blade, 3 bolts for the plastic cover, and 1 bolt for the idler pulley which has the belt around it. The belt looks old and dry, I am hoping that this is my problem!
I have phoned a couple of local places in Ontario (GTA area) and the belt is reasonably priced at about $15 to $20.

Perhaps I am too late, but...
go to the link below
enter the model number of you mower and press search
then select the "manuals" tab at the bottom of the page
and download the pdf for "Toro/Lawn-Boy Walk Behind Power Mower Drive Systems Manual"

It has a chapter on blade clutches, with pictures and instructions on removing/replacing parts, etc.

Good Luck

Here is a link that might be useful: Toro Drive

I'm having the exact same problem! Did you resolve the problem by replacing the belt?

OK, I'm following up on a three year old post, but who knows maybe this information will be useful to someone.

I was having the same problem with my Toro SR4 and I found this thread. I was planning to take it in for service, but mike9476's post inspired me to pop the cover off and take a look.

Sure enough it was loaded with old grass clippings in there. Also the bolt that holds the pulley to the shaft was slightly loose. After I resolved those 2 issues and put it all back together it worked fine! No new belt needed in my case.

This is helpful information; it saved me from dropping the clutch assy when I found the belt outside its keepers. I had difficulty removing the pulley because the bearing had disintegrated. So, always check the pulley/bearing assembly or you may not be able to remove it in subsequent failures. I'm changing both the belt and the pulley,

Still helpful in 2020. Super dependable mower, thanks for this thread!

Going to pick up an SR4 tomorrow with the same symptoms. Never worked on one before but it can’t be much harder to do than a Honda HR-214 blade clutch, guess if I can get one of those sorted out a good ol‘ TORO should be pretty straightforward!

Yeah their all very similar , the majority of these clutch blade units and belt drive units get very little attention until the clutch bearing or belt is damaged due to dirt , debris . Seasonal inspection and cleaning and lubrication as required to the spring and pivot linkage is paramount .

Ssewalk: "Yeah their all very similar" ???? Am I thinking of a different Toro blade clutch??

The toros with Suzuki's that i have come accross have 2 disks(1 to engine, 1 to blade) with a belt in between them. Engage is tightening the belt. This vs honda where it has a clutch plate on the shaft- expensive when need to replace vs just replace the belt(Toro).

HU-238879374: When i came accross hondas with this worn, it cost a pretty penny to get the new clutch.