Onan engines.

[WheelhorseBob 1,550]

Well I've owned a few Wheel Horse's over the years an liked them all. They have had Kohler singles and Briggs Twin's. (Work Horse) Anyway I have always lusted after a 520H with it's Onan 20hp power plant. (got a beauty with 318hrs) Suffice to say I like to read up on things and have read everything I can find on the Onan's. What a mixed bag of opinions. Everything from it won't make 500 hour's without puking a valve seat to they are good for 3000 hr's with proper care. I also read somewhere that Wheel Horse chose Onan because they were the cheapest alternative. That seems silly as every quality garden tractor MFG. used Onan power. Wheel Horse, John Deere, and Case Ingersoll to name three. Seems if you maintain your Onan and keep it clean it will be as good if not better than the rest. Thoughts.       

[horseyheaven 113]

I think they are good engines.  I bought one that had not had the cooling fins cleaned regularly.  It lost a seat.  I found another good block and fixed it .  I love it.  2 things that are simple to help them live a long life.  It seems to always be the back cylinder closest to battery because of lack of air flow due to belt guard and oil filter.  I put 10 one inch holes in the belt guard to allow hot air coming off cooling fins to flow better.  I also put a remote oil filter on to improve air flow to the cylinder head.  Overall, I am very happy with my 520H, 520HC, and 416-8 all Onan powered.  The 520H had the issue at 1275 hours.  I now have 1400 hours on it mowing with 60” deck.  The 520HC runs a 60” mower and 42” snowblower currently has 1100 hours and no issues.  The 416 has 1300 hours and no issues.  Listen for a ticking sound when running, that is a sign a seat is coming loose.  I ran mine too long that way and messed up the block.  I bought it and it had a slight tick.  I thought it was something else, not knowing valve seats are an issue.  Valve seats can be fixed if the block is not too messed up.  Hope this helps.  I learned a lot about that one in a short time.  318 hours is amazing.  Good luck, enjoy.  They are a pleasure to use.

[bc.gold 3,403]

1 hour ago, WheelhorseBob said:

Well I've owned a few Wheel Horse's over the years an liked them all. They have had Kohler singles and Briggs Twin's. (Work Horse) Anyway I have always lusted after a 520H with it's Onan 20hp power plant. (got a beauty with 318hrs) Suffice to say I like to read up on things and have read everything I can find on the Onan's. What a mixed bag of opinions. Everything from it won't make 500 hour's without puking a valve seat to they are good for 3000 hr's with proper care. I also read somewhere that Wheel Horse chose Onan because they were the cheapest alternative. That seems silly as every quality garden tractor MFG. used Onan power. Wheel Horse, John Deere, and Case Ingersoll to name three. Seems if you maintain your Onan and keep it clean it will be as good if not better than the rest. Thoughts.       

 

Bad reputation on the all aluminum block which are known to suck a valve seat.

 

My Simplicity 9020 mid 70's and my Allis Chalmers 720 both have the CCK Onan cast iron block, the 9020 lived a hard life before I purchased it. The 720 came from oil rich Alberta, previous owner had all the implements but  blew the hydro by towing the tractor trying to start it with a dead battery.

 

Awesome engines with plenty of power and torque. compared to other small engines in the same horse power range the Onan is not  going to win any awards for fuel economy. But she'll outlive her competitors giving you years of faithful service.

 

The cast iron Onan engines use shell bearings on the connecting rods, and you can get undersized mains bushings. The all aluminum engines use an aluminum alloy connecting rod, if you have to grind the crank you'll have to purchase the corresponding connecting rod

Edited July 24, 2020 by bcgold

[ebinmaine 70,826]

@JCM and @WVHillbilly520H could weigh in here... 

[WVHillbilly520H 10,376]

As of yet I bought my first 520H brand new in 1998 and used (abused) it 4 seasons basically non stop for many years it now has 760 hrs and is my primary snow chucker then I bought my second one used and it truly was abused and left die at only 236 hours before I saved it now has 370ish hours it is a garden and "trim" mowing machine I do not take it easy on these machines I did not relieve the belt guard or move the oil filter... Good quality oil and filters plus changing when recommended has been my saving grace good luck with your new ONAN powered toy you'll love the sound only that Onan can make up on the governor in heavy grass or snow.

[tom2p 2,394]

I've been cutting 2-3 acres (primarily) with an Onan powered 416-H for around 17 years 

 

has around 1000 hours 

 

zero issues 

 

best garden tractor I've owned - and probably best vehicle I've owned 

 

also have 312-8

 

if you cut a lot of grass - the difference between the 312 and 416 is significant 

 

so much that I purchased another 416 

 

[Ed Kennell 40,564]

I picked up my '88 520H that was on it's way to the scrap yard with920 hours on the meter.      It ran , but surged constantly.

 

I removed the tins and found an oil leak under the oil filter mounting plate that had blown oil across the rear cylinder cooling fins totally clogging them with  a sticky mass of grass clippings.

Removed the heads and decarboned.  Luckily the valves, seats, and pistons looked good.

Cleaned the carb...three times until the surging stopped.

I did vent the belt guard and added a heat collector that pumps all the heat into the cab.

Added a foot motion control,  loaded tires, wheel weights, chains, and a 54" snow blade.

It is a beast of a snow remover.

[Darb1964 1,093]

A well maintained onan is hard to beat, I bought a 520-H new in 1989 hour meter stoped working with 777 hours on it fifteenish years ago. The amount I used it, did something almost every day, I'm guessing but must have close to 3000 hour's on it and still running strong. Had the dealer put a a new carb on it three years ago, other than that just good regular maintaining. Dealer said it was good for another thirty years. It lead to my addition, in the last ten years have added nine more, five in the last three months. Not all onans.