Slow Blade Speed on a 42” Mower Deck on a C120

[Matt A 0]

I would like a little help figuring out an issue I have with a 1976 C120 with a 05 42ms 02 mowing deck. When I engage the blades they are a slow to come up to speed (maybe 5 to 10 seconds) then slow down quickly when I begin mowing. The cut pattern is even, so I think all three blades are spinning similarly. The issue seems to be getting worse so that the blades spin so slowly they will not cut longer grass (6” or so) and hardly cut short grass. 

 

I suspect the deck belt because it seems a little loose, but it’s almost a new belt. It got a lot better when I treated the belt with some belt dressing, but that wore off after a little while. 

 

I think maybe the tension spring is getting week and is not keeping the deck belt tight enough. Although the middle blade is not cutting any better than the outside blades. I mention that because if the deck belt was slipping I would think the middle blade would still have full power from the PTO drive belt. 

 

So my question is, where should I start trouble shooting? Should I replace the spring first? The pulleys are also worn enough that you can feel where the belt rides, but I am not sure how worn is worn out. I will add some pictures in case that helps. 

 

Thanks for any thoughts! As a side note, I joined here a while back but until now I have not had much to say. I have enjoyed and learned a lot from this forum!

 

Matt

[Razorback 1,035]

If mine was doing that, I would suspect anything from the PTO to the deck. Is the PTO engaging properly? If that was not adjusted properly, that in itself could be a cause. Next, I would check the mule drive and belt..... good tension there? Then work your way to the deck.

 

Something there is not right, obviously...

[oliver2-44 9,695]

Just a thought on one thing to check.  The idler pulley mounts on a bar that slides. It has these plastic washers & bushing that help it slide.  Give that deck a good cleaning and check if these are worn out.  These are available from Glenn Petti and possible Wheelhorseman 1000 parts and more.

 

[Lee1977 6,647]

The stamped steel pulleys if it has been used lone enough will ware to a point that they will no longer cut heavy grass.  I had that to happen to my 48" deck on my C-120.  You nreed to check the PTO adjustment to makue sure it is not slipping, and that the drive belt is tight enough to keep it from slipping. Check the deck for cracks around the spindles. Make sure the spring belt tightener on the deck is going it's job. If everything checks out and the blades are sharp I would say the pulley are worn out.  I had to replace all the deck pulleys to get my deck back cutting as it should.

[daveoman1966 3,745]

1)... PTO bell adjustment...PTO bell must NOT slip at the disc.  2). Belt tension from PTO thru mule drive.  Should deflect 1/2- 3/4 " midway of the PTO to Mule Drive.  3)...Belt slip on the mower deck.  Idler SLIDE bar must move freely back/forth...clean out all debris.  DO NOT grease the slide bar...grease is a dirt magnet.   

[Matt A 0]

Thanks all for the suggestions! I am going to check the PTO again, but I did not notice any slipping there. I replaced the friction plate last summer and I know the PTO drive belt is tight. So looking at the slide and pulleys is a good next step. It seemed to slide freely, but replacing the bushings makes sense. 

 

How likely is it that the spring has lost tension? If the PTO is good and the slide moves freely, it seems like the problem is the spring or the pulleys. The spring is a lot cheaper so I was looking at that first. But maybe I am wrong to suspect the spring. 

 

Thanks for the help!  

[Lee1977 6,647]

One other thing that can cause it not to cut is if the double pulley is loose that can cause the pulley to slip on the shaft.  Put a wrench on the bottom of ths spindel and tighten the nut on top of the pulley. The pulley is only held my tension. If it is worn pulleys you might be better off just look for a good used deck. Save your old deck for replacement parts. 

Edited August 11, 2019 by Lee1977

[Razorback 1,035]

17 minutes ago, Lee1977 said:

One other thing that can cause it not to cut is if the double pulley is loose that can cause the pulley to slip on the shaft.  Put a wrench on the bottom of ths spindel and tighten the nut on top of the pulley. The pulley is only held my tension. If it is worn pulleys you might be better off just look for a good used deck. Save your old deck for replacement parts. 

That’s good to know.....