How mowing can destroy your ONAN

[JackC 617]

Most of us are aware of how the flywheel screen gets plugged with grass when mowing and the need to keep cleaning the grass off.  I was mowing some taller grass with my 1995 416-8 and had the deck raised higher than normal.  In addition to grass clippings going out the exit chute of the deck, I could see grass clippings blowing out from under the front of the deck and getting sucked into the flywheel screen.  The screen was getting plugged after only about 5 minutes of mowing.  

 

 

We need to invent something to minimize this problem.  Something that does not distract from the appearance of the tractor would be good.  Possibly a rubber skirt around the inside of the deck shell could minimize the clippings going out other than where they are supposed to which is the exit chute.  Another possibility is some kind of baffle under the tractor to keep the clippings from getting sucked up into the flywheel screen.  The flywheel screen is on the left and the exit chute is on the right so if clippings can only go out the chute the problem should be minimized.  

 

 

My guess is that many of the ONAN failures were caused by the flywheel screen getting plugged with grass clippings and the engine overheating.  Instruments that could help that are not on the machines are a temperature gauge and a cooling air flow sensor. 

 

Here are some pics of the problem and these are after only a few minutes of mowing.  Also notice the clippings on the front axle in the second picture.  The clippings should only go out the chute on the right.

 

 

 

 

 

 

 

 

 

[WH nut 553]

Thats a real common problem. I think the only way to solve it would be to make some type of baffle for the motor. Even if you baffle the deck the fan has so much sucking its still going to plug. I dont know how you would do it without distracting from the looks.

[varosd 1,185]

That is extreme grass!!    I agree, for me the real issue is leaf season!  I am forever leaning forward on the seat to scrape off all the leaves, pushing back on the seat at the same time!!!

[MalMac 1,331]

Jack C that pic. shows why I quit using my 520 for mowing and leaf pickup. I used to run around with a small broom in my left hand while operating to knock off the leaves. I would go maybe 7 to 10 feet when doing leaves and then lean forward a sweep them off. Did the same thing when mowing grass. One day I finally had enough of the Onan for mowing or leaf pickup and switch back to using my tractors with Kohler's. I only use the 520's now for running the 2 stage or pulling. That grass pickup is nothing but a death sentences for the Onan. I don't know how many times I have been driving out and around and noticed someone with a 520 or 416 with a totally clogged grass screen and they were totally oblivious to it. Made me want to jump out of the car and run over and say "Hey your killing that Horse, stop and clean it off !! Before you blow it up!" But if the person really is just or average homeowner that is just trying to mow their yard I am sure they would not be aware what will happen till the big Boom or why is my motor sounding like a bucket of bolts.

[squonk 41,016]

Your going to have to make  a snorkel like the swamp buggys use!

[MalMac 1,331]

I can see it now, big shroud over the grass screen then a large tube straight up in the air about 6 feet to gather fresh air without clippings or leaves. Be great in an open field. Might have to worry about sucking in the occasional bird though.

[nylyon-(Admin) 7,242]

My Onan does NOT do that, but my Kohler does.  I am pretty sure that the reason is the side discharge deck.  My 414 has a SD deck and I constantly have to clean the thing.  Under the hood, axle, air filter and of course the engine screen.  My Onan powered 416, has a rear discharge deck (and sometimes recycler) and while there is some debris on the screen, it has never looked like the above pictures.  The SD deck shoots clippings out the left front.  I wonder if putting a rubber edge on the SD deck would help prevent this from happening?

[MalMac 1,331]

You make a very interesting point on the side discharge VS the rear. I have never used a rear with a Onan only a Kohler powered machine. I do believe I will have to try this theory out. Could shine a whole new light on the subject. It really seems to make a lot of sence. Because the clippings come from the left front on the SD.

[nylyon-(Admin) 7,242]

I put the SD on my 416 ONCE and only ONCE, it was removed for this very reason.

[MalMac 1,331]

I do know that Toro offered a "Leaf Baffle" for the 42" SD. It was supposed to help the leaf blow out from underneath the front of the deck. Why it was just for the 42 and not including the 48 I have no idea. I thought about getting one a few years ago and the price was absurd. From what I could tell was all it did was in closed the deck more to help create more of a vacum to help the leaf vac blower to pick up more.

I do know that Toro offered a "Leaf Baffle" for the 42" SD. It was supposed to help the leaf blow out from underneath the front of the deck. Why it was just for the 42 and not including the 48 I have no idea. I thought about getting one a few years ago and the price was absurd. From what I could tell was all it did was in closed the deck more to help create more of a vacum to help the leaf vac blower to pick up more.

Why in the heck have I got a double post in the same post?

[StWeiler 6]

I'll be watching this thread closely.  I'm about fed up with the constant need to clean the screen myself.  RD decks are virtually impossible to find around here.  There has to be a solution for making the 42" SD decks more efficient.  Possibly weld a baffle system in like on commercial Zero Turns?

[Lagersolut 648]

My Kohler CH-15  on a classic GT isn't much better,  I actually made some changes to the wrap around shrouds ( cut the exaust side of the shrouds ) becuase it was limiting air flow ,  the grass and dirt was accumulating and packing in the finns , it also had an air induction going from the bottom of the blower housing into the air cleaner, after a few mowings the air cleaner was literally packed with grass and dirt ......took the induction tube out and closed both holes with sheet metal .

  Even with my changes I still need regular trips top the air compressor to keep things flowing .    

 

Motor runs a lot cooler with my changes .

[stevebo-(Moderator) 8,330]

I get minimal in the screen when using mine with the 60 inch deck. May be because the deck is further away and shoots the grass to the right hand side of the machine. I think that is the same on the 48 inch but the 42 shoots it to the left.

[Hodge71 664]

I used to have the same issue. This year I bought a 42 inch rear discharge deck and the problem is gone. I had to drive all the way to Locke NY from my house but I got a decent deck for the 6 hour round trip

[WH nut 553]

I get minimal in the screen when using mine with the 60 inch deck. May be because the deck is further away and shoots the grass to the right hand side of the machine. I think that is the same on the 48 inch but the 42 shoots it to the left.

All my 42 inchers shoot to the right. I had my 520 out cutting realtivley short grass and it was collecting also have to clean the screen every few rounds

[dbartlett1958 96]

My 416 with a 42" Rear Discharge stays pretty clean.  I have no experience with the SD decks on a Wheel Horse.

[slammer302 2,155]

Rear discharge is the only way to go i would rather use a smaller rear discharge than a bigger side discharge it spreads the grass clippings more to and u can mow around things on either side of deck

[tiggercl 28]

It can be quite dry and dusty on my patch.

 

Using the 60" right discharge on the 520H, I find it helps to adapt the mowing pattern to suit the prevailing conditions (where possible).

 

1. Accept any wind from the left on the long runs.

2. Try to keep the chute downwind when making turns. 

[MalMac 1,331]

Well from reading other post that little secret that Karl reveled about the RD VS. the SD has been discovered by other members here. Sounds like RD is the way to go if you have a tractor equipped with a Onan. Is there a cover up here that's been exposed? Did Toro find this out after the fact and it was too late in the production process? Seems a little fishy to me. How could that large a company make that kind of oversight? Or was it the thought process of " Oh well " You would think there would be all kinds of testing done. If they did discover this and just state that the owner should keep the grass screen clean I suppose that would cover them. They just left the little part out about cleaning it every 20ft or one pass of a small yard. Then there again there is a chance of me having a over active imagination. The fact is the fact that Onan sucks in grass so bad that it is a detriment to it's self. " Inquiring Minds Want To Know"

[Ken B 3,164]

I agree that this was probably the demise of many an Onan. I mow a little over an acre a week with my 520. I too have a 42 inch side discharge deck on my 520. Every few passes I need to clear the screen on mine as well. I bet there are tons of people out there who never bothered to do this. They either didn't know any better, too lazy or they just didn't care. I'd like to find a nice 48 inch side discharge to cut down a little on how long it takes. There are some benefits to a rear discharge deck but I feel the side discharge does a better job, and I have both. I'll just continue to keep the screen clean and keep on mowin with my 520 until the day she dies, suckin gas and suckin grass! (224 hrs on the clock and countin)

[WH nut 553]

A 48 in SD wont help

[ronhatch 406]

I think it would be less of a problem if the screen spun with the flywheel.

[nylyon-(Admin) 7,242]

One habit I have gotten into is I take my hand blower and blow all the clippings off the machine, and I spend a lot of time on the engine from the PTO side to get the dirt out of there. 

[slammer302 2,155]

Me to

[boovuc 1,090]

Ahh but one also has to worry more about over heating and jamming your fan and cooling fins on the hydro with a rear discharge deck. (Not an issue with an 8 speed).

It shouldn't be too difficult to fab a snorkel out of ventilation flex hose. I've seen it in 12, 14 and 16" diameter. Would it look nice............nope!