520 HC grass cutting help needed

[Velocityboy 5]

G’day everyone.  I have a 1990 520 Hc with 60” deck that is not cutting grass well.  When I got this machine 6 years ago it was awesome, I could run around at 1800 revs and it would cut like a champion.  For the last 4 years it takes very little length of grass to stop it cutting. The deck just gets clogged with grass and won’t blow it out the shut so it dosent cut at all until I wait for the grass to clear.  I have had several sets of blades on it trying different types, the belts are not slipping and in good condition, I just put a new PTO clutch on it, I regularly pressure clean under the deck, none of this has made a difference.  I’m completely lost now.   Does anyone else have trouble? Any ideas?

[wallfish 15,925]

Of the 2 520s I've had, the pulley groove on the PTO was worn to the point the belt would slip on both of them. Those big 60" decks take quite a bit of torque to power them so the belt can slip and it wears the pulley. If the belt slips long enough it will wear the pulley groove until the belt bottoms out.

Take a closer look at the pulley groove. It's not easy to see. Try changing the belt to the other groove and test run it in the grass.

It took me a few runs with a 2 stage snow blower and checking through everything else to finally figure out that worn groove was the problem.

If that PTO bell is getting extremely hot that's an indication the belt is slipping. 

[Ed Kennell 35,799]

2 hours ago, Velocityboy said:

I could run around at 1800 revs

The Onan should be run at wide open throttle (3600) for proper engine cooling and mower efficiency.

[Velocityboy 5]

Thanks for the replies.  I have had 2 pto bells on it that look good and I have replaced the main pulley on the deck because of that problem but I will check again.  The blades definatly sounds like it slows down but I’ve never been able to detect any slippage anywhere.   I know it should run at a higher speed but I was demonstrating how easily it used to cut but 3600 sounds like a lot should I really be running it at that speed? I’ve never run it more that 3000. 

[Ed Kennell 35,799]

In addition to checking the PTO pulleys for wear as John suggested, I would look closely at the deck pulleys and the deck belt tensioner system.  Make sure the tensioner slide bar is free and the spring is strong.      You should also have the spring loaded mule drive.  Make sure the spring is strong.

The clogging you describe may be due to one or both of the outside blades slowing while the center blade continues to spin at proper speed. 

 

1800 RPM for mowing is not healthy for the Onan's cooling and lubrication.     I run mine at 3200 only because it sounds better than 3600.

[lynnmor 6,783]

Be sure that the belt is on the inner grove of the PTO, the PTO clutch is firmly engaged and rev the thing up to 3600 RPM.  I have always mowed this way and it is in your owners manual.  Slow turning blades actually increase the torque on the belt and leads to PTO clutch slippage.  Improperly sharpened blades can add to the problem.  You are NOT doing the engine a favor by running it too slow. 

[Darb1964 1,014]

You want to check that you blades are on right, wouldn't be the first time they were put on backwards. Run that thing wide open like others have said, you can do more damage too the Hydro and the Motor, it's designed too run and work at 3600. RPM. They are hard working industrial motors, clean oil, gas, and Air filter no worries.

[Skwerl58 634]

On my 414-8 I had an issue like you have reported and it was in the idler pulley on the deck. The pulley bearing was shot and wallowed out allowing the belt to slip. My blades would slow in thicker grass until I found the problem. A local mower shop had a replacement puley, added a new belt, cleaned the deck up and has been doing great since. Also like others stated for the deck to operate correctly run it at 3600 rpm. 

[peter lena 8,069]

@Velocityboy  realise that a 60 " deck is a beast  , for service , how many times have you had that off the tractor for a  thorough  look over ? would bet its a combination of issues / problems , surely not just one thing , agree  with @Skwerl58  with those tiny pulley bearing failures . dare I  ask what you use for bearing lubricant ?  every function of that has to be checked out , and improved . also don't know what  kind of cutting you do , lawn / field  etc .  hope this and related feedback  puts you on track , its not just a quick fix , its a set up change  for what's going on . autopsy  time , pete 

[Velocityboy 5]

Thanks again everyone.  Well it’s pretty clear I’m running it too slow, I only ever run it around 2500-3000 max. Next mow I’ll up the revs. I have just fully reconditioned the motor so it’s up for the work.   I have had the deck off several times and spent a fair bit of effort maintaining it but I have been thinking of replacing all the pulley bearings just for the sake of it so I might do that too. From memory aren’t the deck bearings all sealed type?  I remachined the groove in the primary deck pulley to take the ware out of it a few years ago but it made no difference to the problem then.    I guess a whole system check is in order. 

Edited August 27, 2022 by Velocityboy
Spelling.

[peter lena 8,069]

@Velocityboy  stop right there !  was hoping you were going to say that ! https://www.autozone.com/greases-and-gear-oil/lubricant-   every one of those related bearings , should have this grease in them , the related bearings , typically have wide rubber side shields on them , small pocket flat screwdriver , carefully pop of  seals , wipe out original grease , flush with carb cleaner ,total clean, repack same amount of lucas X-TRA HEAVY DUTY CHASSIS GREASE , 560 deg , anti sling , polyurea rated , did my spindle bearings , mule drive bearings , also did my deck related pulley bearings , if you can get same size / type pulley , with a bigger bearing , that makes the upgrade very easy , just add a bushing , and do a grease swap ! also clean out and LIGHTLY  regrease the pto needle bearing cone . hope you are on the recovery mode , have lots of hours on my recommendations , it works , pete    

[lynnmor 6,783]

4 hours ago, Velocityboy said:

Well it’s pretty clear I’m running it too slow, I only ever run it around 2500-3000 max.

 

From memory aren’t the deck bearings all sealed type?

 

3600 RPM, not just up it.

 

There are grease fittings on all three spindles, for the side ones, look in from the side under the belt guards  and you should see them unless someone had the spindles out and turned them the wrong way.

[Velocityboy 5]

Learning new stuff here😁 thanks. 

[peter lena 8,069]

@lynnmor  , yes those bearings are sealed , the big question is , what kind of generic  grease is in them ?  one thing is for sure its NOT A  HI TEMP RATED GREASE , thats why they whine  and fail , and add a total slow down to your  deck operation . do a very easy side seal removal  wipe out grease , finish flush with carb cleaner , repack to same amount , with a 560 deg rated grase , anti sling , polyurea rated ( recovering ) grease . do that to every related , deck bearing , and mule drive bearings ,also , don,t forget the pto needle cone bearing . you have just eliminated bearing drag / noise , and will notice a very significant  ease of mower function . done that on my 3  horses . if you are replacing any bearing , VERIFY THE LUBRICATION STATS ON THE GREASE . only my own experience . pete

[lynnmor 6,783]

3 hours ago, peter lena said:

@lynnmor  , yes those bearings are sealed , the big question is , what kind of generic  grease is in them ?  

I bought my 60” deck in a well used condition about 22 years ago.  I totally reconditioned it and replaced the spindle bearings with ones that had the same number, I believe that they had only the outer seals, not sure.  This deck was used to mow about 3 acres, some of it rough.  I used the red grease from TSC in the grease fittings and never had a problem.  The deck is now semi-retired with a zero turn doing nearly all the work.

[peter lena 8,069]

@lynnmor   red grease is good stuff ,  like it in aerosol form , great on lots of linkage movement points . zero turns have really taken over . pete

[Velocityboy 5]

 Just an update if anyone is interested.  I pulled the deck off and all the spindle bearings where nice and free but I stripped and cleaned them and regressed with the right grease anyway. I inspected all the pulleys and notice what I thought was minor wear but I decided to machine them all back to the correct angle. I am now running a B section belt so that will over kill it. I faced the PTO clutch as well.   It cuts like a champion again.  It took a little getting used to running it at 3600rpm but it’s a demon now.  In general I think I’ve been a bit soft on it, not wanting to rev it hard, and I think I’ve been having the PTO engagement pressure too light.  Thanks again to everyone who helped me out.  The pics are of a couple of pulleys that had ware, I don’t really know what’s acceptable so I just cleaned them up anyway.  One pick is after machining.  

Edited September 12, 2022 by Velocityboy
Spelling

[Lee1977 6,217]

I completely wore out a set of pulleys on my 48" deck to the point that they would not cut heavy grass. Once the grass got too high or thick the deck just quit cutting. 

[8ntruck 6,376]

Thanks for the follow up.  I'll try to remember this solution foe future troubleshooting.

 

Where did you get the pulley contour gages?  Seems like those would be handy things to have when messing around with old belt driven machinery.

Edited September 12, 2022 by 8ntruck

[Velocityboy 5]

6 hours ago, 8ntruck said:

Thanks for the follow up.  I'll try to remember this solution foe future troubleshooting.

 

Where did you get the pulley contour gages?  Seems like those would be handy things to have when messing around with old belt driven machinery.

I made the gauge, it’s just a piece of 1/8” steel cut to 40 degrees. 

[lynnmor 6,783]

The included angle varies a bit depending on pulley size.  Belts usually have a nominal angle of 40 degrees.

 

Per the Machiners's Handbook, 20th edition:
Light duty V-belt Sheave dimensions
2L
Effective Outside Diameter in inches
Under 1.5-- 32 deg. width at full dia .240
1.5-1.99-- 34 deg. """"""""""""""""" .243
2.0-2.5-- 36 deg. """"""""""""""""" .246
over 2.5-- 38 deg. """"""""""""""""" .250
depth o f groove .250

3L
Effective Outside Diameter in inches
Under 2.2-- 32deg. width at full dia .360
2.2-3.19-- 34 deg. """"""""""""""""" .364
3.2-4.2-- 36 deg. """"""""""""""""" .368
over 4.2--38 deg. """"""""""""""""" .372
depth of groove .406

4L
Effective Outside Diameter in inches
Under 2.65-- 30 deg. width at full dia .485
2.65-3.24-- 32 deg. """"""""""""""""" .490
3.25-5.65-- 34 deg. """"""""""""""""" .494
over 5.65-- 38 deg. """"""""""""""""" .503
depth of groove .490

5L
Effective Outside Diameter in inches
Under 3.95-- 30 deg. width at full dia .624
3.95-4.94-- 32 deg. """"""""""""""""" .630
4.95-7.35-- 34 deg. """"""""""""""""" .637
Over 7.35-- 38 deg. """"""""""""""""" .650
Depth of groove .580

groove angle is included angle
 

[Handy Don 10,609]

On 9/12/2022 at 4:13 PM, lynnmor said:

Per the Machiners's Handbook, 20th edition:
Light duty V-belt Sheave dimensions

Thanks for posting this, Lynn. I never noticed that the angle varied based on the diameter of the pulley.

And thanks @Velocityboy for the images with the gauges in the grooves--very helpful!

[peter lena 8,069]

@Velocityboy   down under !  terrific    swapping  issues so far apart ,https://www.google.com/search?q=lucas+hd+grease&rlz=1C1CHBF_enUS866US866&oq=lucas+Hd+&gs_lcrp=EgZjaHJvbWUqBwgCEAAYgAQyCggAEEUYFhgeG  more than anything , have found COLLECTIVE ROTATIONAL DRAG  is what eats , belts , clutch units and  any pulley set up , those 60,s have a major problem of  DISCHARGE , collective build up , and failed lubrication to the drive spindles . that Lucas  green has a 550 deg  flash point , will stay with just about any issue . would also require  a bearing clean out , and re grease . cross contamination   of lubricants should be avoided . almost think a different set up , like an open flail mower , might be better for you . that singular side discharge , along with bearing drag / other related areas , not the same set up , but I ONLY HAVE REAR DISCHARGE DECKS . clutch unit , pulleys , lube failure , wish I could give you a better answer , pete

[kpinnc 10,736]

On 12/3/2023 at 11:22 AM, peter lena said:

those 60,s have a major problem of  DISCHARGE

 

Agreed. By comparison, the 61 inch deck on my Scag has a side discharge chute more than double the size of the Toro 60. I can mow pasture grass that is a foot tall without any clumping. It really makes a difference.

 

Not disrespecting the 60SD at all. It gives a beautiful cut. It's just that a larger discharge would make it perfect.

 

 

Edited December 6, 2023 by kpinnc

[peter lena 8,069]

@kpinnc agree with that , every mower deck has its , good /  not so good areas .  thats the main problem , along with the ground cover you are cutting . thats where a flail type set up , excels , regular deck  type , and related drive set up , is easily fowled , and slowed down , increasing drag everywhere. recommend anyone dealing with a constant / repetitive problem , to think about a change ,of deck type , related , if I  had an old beater deck , might experiment with more discharge . cutouts . your SCAG unit sounds , on point , Pete