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MalMac

Onan life exstending thought?

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MalMac

I have notice and have also saw it here on RS that the Onans seem to fail more on the a Wheel Horse application than any other use. I know some of the other brands of garden tractors have had their issues with them but not as much like the Horse has. With that being said with alittle observation on my own 520's I have notice that the back cylinder can not get enough air moving past it do to the belt guard being int the way. Just a though here but has anybody shorten the guard or maybe cut some vent holes in it? Shortening would work but I don't think that would be the safe thing to do. I have an extra belt guard laying around think I might just mill some vent slots though it. Just wonder how much heat will come out and make it to uncomfortable to operate. Any thought here?

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wh500special

Years ago on the Yahoo forum somebody suggested doing exactly the same thing (cutting the slots) to provide a pathway for the hot air to escape. I think it's been done and I'd presume there are no demerits - other than having a few holes in the sheetmetal - to the surgery.

I don't have a running list of Onan related problems that would provide any statistical significance, but my memories of stories of dropped valve seats in 520's and 416-O's suggests that it usually happens on the rear cylinder. My assumption has always been that the belt guard restricts the flow a bit, clippings build up, the cylinder runs hot, the aluminum block expands more than the steel seat, and the seat pops out.

Presumably, however, both WH and Onan would have had to approve the engine/tractor combo for reliability. If they did any testing they must have been satisfied with the results, but it is really hard to account for what level of preventive maintenance any unit might see.

The only 520 I presently own is an 8-speed that sees no work what-so-ever. If I end up with a worker 520H I anticipate cutting slots of my own.

Steve

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300zx

My neighbor and I just put a P220 Onan engine in his Toro Ground Master. It replaced a B48G (20 hp) Onan which look from the outside to have essentially the same short block. The major cooling difference I noticed is that it used an oil cooler that was connected in the same place as the oil filter and mounted behind the engine (what we would consider the PTO end). The mower and pump are driven from the fly wheel end. The mower came from a golf course and has 3800 hours with no indication that the motor was rebuilt. Extra cooling some how could be the secret to long life. I doubt if the golf course maintenance ever included pulling the engine tins to clean out the fins and other than oil build up, they weren't that clogged.

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Shuboxlover

VEEEEERY interesting.....how hard would it be to add an oil cooler to a 520-x???

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Forest Road

If the oil cooler adapter and filter don't have enough room you might consider relocating the filter. I doubt that a cooler and filter relocation kit would be over $100. send us pics.

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stumpkicker

Forgive me ! But Onans are not made any more because of the poor quality they put out for a few years and failed all their customers by doing so !

(Knowing someone has a different response to my reply)

The P220 is top of the line JUNK ! I bought 3 of them in a 6 year span! for a skid steer!

Had them rebuilt and that costs more then buying new!

I need another one now looking for another reliable brand ! Most likely foreign !

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