520 Service

[HokieAg07 129]

Well today was the day to get the 520 ready for the season. Engine and trans oil changes, tune up, de-carbon the heads, and adjust the valves. This is the first time I have torn this tractor down since I got it last year. '96 model with 430 hours. Engine was very clean inside with so little carbon that some Gum Cutter and a towel removed it. Valves were out about 0.001-0.002. Did manage to break off a bolt in each head so that prevented me from getting done today. 

 

 

 

 

About the extent of the carbon in the heads

 

 

Pistons/Valves

 

 

Only took some solvent and a rag to get them clean

 

 

 

Broke of bolts

 

 

[Kelly 1,030]

That looks like a well kept machine, and your doing it right by keeping up on the service that most often never gets done.

[Wheelhorse84 87]

So to do that job you need to remove all that stuff and engine?

[HokieAg07 129]

Only way to get to rear cylinder head

[Wheelhorse84 87]

Wow. I wonder how much the dealers charge for that job.

[leeave96 487]

I need to de-carb the heads on one of my 520H tractors and am not looking forward to it.  I have a Kohler Command twin on another color tractor of mine and it seemed like every other bolt broke taking the tin off of it to get to the heads.  I know the importance of decarbing the heads on these Onans, but fear, as you encountered, shearing a bolt and opening another can of worms.  My gut says, if it ain't broke. don't fix it and I wonder to what extent one can deal with carbon with additives and leave a good running engine intact.  I really like the Onans in my Wheelhorse tractors, but somehow if I blow one, I will likely replace it with a nicely rebuilt Kohler K or Magnum single cylinder cast iron engine.

 

Good luck,

Bill

[MalMac 1,332]

leeave96 I am right there with ya. I have got a 520 that needs to have all the de-carb thing done but I hate to tear it down. It is runnings so strong ever since I got the carb good and clean. The old adage If It ain't broke don't fix it keeps ringing in the back of my mine. It's kind of a catch 22 if you go and do the proper maintance you will cause more problems. If don't do the maintance you will cause problems down the road. I guess ethier way you gona have problems after all it's a Onan. Great motors till you work on them or don't work on them. I'll take my old K Kohler's any day. It's just hard to beat that Onan power though.

[ericj 1,578]

the problem with the bolts that broke off in the heads is that they don't go straight down in they go in on a slight angle so when you drill them out be careful, don't ask how i know this, but in the end it don't really matter because i have some heads that were drilled straight and retapped and works okay, but if you can do it right you should try. just a heads up

 

eric j     

[jjstuds 0]

i work for a gm dealer, and i recently just bought a 93 520h with 286 hrs. we use a additive that we pour in the intake to loosen up carbon on the valves and intake. would something like that work on a onan engine?

[Tankman 3,520]

 

i work for a gm dealer, and i recently just bought a 93 520h with 286 hrs. we use a additive that we pour in the intake to loosen up carbon on the valves and intake. would something like that work on a onan engine?

And Sir, "What is the additive called?"

[HokieAg07 129]

i work for a gm dealer, and i recently just bought a 93 520h with 286 hrs. we use a additive that we pour in the intake to loosen up carbon on the valves and intake. would something like that work on a onan engine?

 

GM Top Engine Cleaner is good stuff. I would equate it similarly to SeaFoam. Definitely cant hurt as a regular maintenance practice. I just wanted to see the engine internals for myself 

[puddlejumper 67]

 Question, definitely not a suggestion, I have seen a few older mechanics one was a head mech at a ford dealership, and heard a few talk about warming a car engine up wrap her up good and tight and pour water in the carb to the point of almost killing it to decarb pistons and valves has anybody else seen or heard this and has anybody tried it on a small engine. This ought to get some responses.

[roscoemi 245]

I've heard of it, the steam effect it was called. High pressure steam will cut thru anything. Never seen done though.

[leeave96 487]

I have heard of spraying a waster mist into the carb of a Kohler engine to decarb it.  Never tried it, don't know if it works - never heard if anyone did this opened an engine head, looked at the carbon, put it back together, then sprayed water mist into the carb and re-looked at the head.

[Dieselcowboy 210]

I went to diesel school out of high school ten years ago and we were taught to do what puddlejumper said only with transmission fluid. So yes it is still a trick of the trade.

[jjstuds 0]

tankman,is called top engine cleaner. you pour it in and let sit for a while and start it up and it blows all the carbon out the exhaust. hokieag07, this is my first wheel horse how often should you tear it down to check for carbon build up? puddlejumper, i have heard the same thing but instead of water they used transmission fluid.

[jjstuds 0]

i have another question where can i find a fuel tank meter # 113358 for my 93 520h?

[can whlvr 993]

i wonder if one of those investigative cameras would show anything in there

[rexman72 210]

welcome to RS

[Shynon 7,470]

Had a neighborhood mechanic that used to pour trans fluid down the carburator on a v-8 until it quit. Let it sit for a few hours, then start it up and run down the road to burn out all the trans fluid.( mosquito control in minnesota) He said it cleaned the carb.

[roscoemi 245]

Back in my Army days, my rig had two 3k generators on a trailer. One night one of my guys swapped out gas cans, using a diesel can. Ran the first gen till it quit and then switched the same can to the second one and ran it till it quit. I got them fired in the morning, and when the smoke cleared I had the best running set of generators in the unit!