Just picked up a 520h--advice needed!

[zeedubbya 18]

I just bought a 1991 520h with 60 inch deck--it's a very nice machine, the po was a meticulous record keeper and has all the manuals and receipts since he's owned it. He said it has a little miss but I can't notice it at all. My question is what should I do to it to make sure it lasts me a long time. It has 1100 hours and he doesn't think the Onan has ever been decarboned. Again I think it runs great but I'd like to know what a good solid tune up would entail. Thanks!!

[varosd 1,185]

Zane,

I have not pulled the heads to decarbon my 520-H other folks will chime in with their advice. most obvious is to get the rear cylinder engine cooling fins cleaned of all grass/crud. even between the engine and the mounting plate. coat hanger to the rescue! also the tranny fins as grass can get stuffed under the seat area, change engine and tranny oil often and filters. consider adding vent holes to belt guard to cool that rear cylinder do a search on this subject and some folks drill a set of holes v

[kpinnc 12,138]

What he said...

[JackC 617]

In addition to prior comments I would do a compression test to check for overall engine wear (spec is 75 to 115), then remove the heads and check for carbon deposits and the condition of the valves and valve seats. It should need to be de-carboned and the valves should be checked and adjusted at least every 500 hours, some say every 200 hours. If you don't want to do it have it done. Someone on ebay sells the gasket kit for the procedure.

i bought a 416H with the 16 horse ONAN that had broken a rod on the rear cylinder at about the 1,000 hour mark. I took the heads off and found a lot of crud and worn valves.

Best to be safe than sorry. It would be great if someone would do a video on it or knows a link to one.

I also use a little sea foam in each tank or can of fuel to deal with the ethanol and to help the fuel burn cleaner. I have multiple tractors and I never know how long each one will sit with ethanol (absorbs moisture and gums up) in it so the sea foam works as a stabilizer.

Also check the air input frequently and keep it clean.

[Forest Road 594]

Personally if it runs good @ 1000 hours I'd leave it alone. I have one with similar hours and I'm just keeping it clean.

[gomer gump 8]

just bought a couple 520,s one had 1100 hrs other 800 took both motors out shrouds off both were caked with dirt grass grease ect . took heads off cleaned carbon out valves needed a little cleaning cleaned carbs sea foam works great found loose wires bolts frayed wires ect inside flywheel was caked solid with dirt stator was really dirty cleaned it all up .getting ready to put them both in tractors soon before i pulled them out one motor was surgeing other smokeing a little i had same problem with many tractors in the past an got them to run smooth every time .mainly by just cleaning them up making sure you got good oil , premium gas, good plugs and wires . replace all bad wires , clean all fins soak carb parts in sea foam ,make sure starter is good . when you get the motor running after total cleaning choke out the motor with sea foam till it stalls wait 15 min srart it up it,ll run like a champ make sure your outside for this will smoke alot . also i talked to an ol wheel horse guy '' friend of mine '' on the 520,s they tend to smoke some an use a little oil past 1200 hrs this won,t hurt a thing it,s a horizontal motor rings are gettin a little worn but you still got alot of life left in the motor . you,ll know when the motors had it , but 9 times out of 10 some rummy dummy didn,t spend the time to do general maintence , basicly lazy , and riuned a 5,000 tractor . also the 60 in mower deck i,d dump it an get a 48 or 42 they work ten times better and easier to handle 60 in too darn heavy for that tractor , i dumped mine bought a new 48 and rebuilt two 42 . the 520,s with the gear reduction steering and front mount mower carrier work really smoth i prefer them over zero turns any day more comfortable . the 60 in deck tends to tear up the lifting arm under tractor and the front steering pin an plate assy . just too much for that little tractor buy a 48 in you,ll love it especially with a front mount mower carrier set up right their really smooth u.s.m.c forever semper fi

[SAM58 30]

just bought a couple 520,s one had 1100 hrs other 800 took both motors out shrouds off both were caked with dirt grass grease ect . took heads off cleaned carbon out valves needed a little cleaning cleaned carbs sea foam works great found loose wires bolts frayed wires ect inside flywheel was caked solid with dirt stator was really dirty cleaned it all up .getting ready to put them both in tractors soon before i pulled them out one motor was surgeing other smokeing a little i had same problem with many tractors in the past an got them to run smooth every time .mainly by just cleaning them up making sure you got good oil , premium gas, good plugs and wires . replace all bad wires , clean all fins soak carb parts in sea foam ,make sure starter is good . when you get the motor running after total cleaning choke out the motor with sea foam till it stalls wait 15 min srart it up it,ll run like a champ make sure your outside for this will smoke alot . also i talked to an ol wheel horse guy '' friend of mine '' on the 520,s they tend to smoke some an use a little oil past 1200 hrs this won,t hurt a thing it,s a horizontal motor rings are gettin a little worn but you still got alot of life left in the motor . you,ll know when the motors had it , but 9 times out of 10 some rummy dummy didn,t spend the time to do general maintence , basicly lazy , and riuned a 5,000 tractor . also the 60 in mower deck i,d dump it an get a 48 or 42 they work ten times better and easier to handle 60 in too darn heavy for that tractor , i dumped mine bought a new 48 and rebuilt two 42 . the 520,s with the gear reduction steering and front mount mower carrier work really smoth i prefer them over zero turns any day more comfortable . the 60 in deck tends to tear up the lifting arm under tractor and the front steering pin an plate assy . just too much for that little tractor buy a 48 in you,ll love it especially with a front mount mower carrier set up right their really smooth u.s.m.c forever semper fi

WHAT HE SAID...

[zeedubbya 18]

Thanks for the advice! I really appreciate it--got it running pretty good, but i really think it needs a decarbon and carb cleaning. Will get on it this week as it's out of mowing condition right now because of the front mule drive pulleys bearing roasting. I was mowing along wonderfully when all sudden I see smoke. I thought oh crap there goes a cylinder, but luckily it was that pulley. Got one on the way--I'm wondering if I should do anything with the shaft too? I guess I'll know when I get it off. Anyway, thanks for the advice! I'll post some pics next week when I get the

Computer back up.

[Wheel-N-It 2,969]

Basically what they all said, and my 3cents is from now on use MMO in the gas, 1oz per gallon. Also 1 or 2 ozs in the engine oil. No more than 1oz per quart.