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MalMac

Onan guru's- Need help

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MalMac

Alright I am used to the Kohlers so these Onans are new to me. I have got two 520H's and both have the same problem. They started out running like the carb needed adjustment. As far as I can tell there is not to much adjusting you can do on them. The next thing that started to happen was they began surging or what you would call hunting. They mainly do it at low RPM but one of the tractors even does it at full throtle. I have taken the top of the carb and cleaned what I could made sure what small orffices there is was not blocked. After I did this it would run just fine then go right back to doing the same thing. I put new gas filters on them but it does not change anything. I need someone to step in here that know a whole lot more than I do.

Tim

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Ken B

I'm sure someone else will chime in but I think I read somewhere, perhaps it was a service bulletin about the governors being overly sensitive and there is a correction for it by relocating the spring for the governor. Mine was surging a tad at high rpm's. I added a little Marver Mystery oil to the fuel and ran the tractor for a few miles around the neighborhood and it seems to be totally cleared up now. This is my first Onan, I've only had it since this past Saturday and I'm trying to get to know it. You don't have any vaccuum leaks do you?

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rickv1957

Tim,will engine smooth out if choke is on partway to richin fuel mixture,if so may need a good carb cleaning,if not mabe govener adjustment assuming engine is in good tune otherwise,Rick

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MalMac

Rick, Some time using the choke with will help. Mainly at lower RPM.

Tim

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nylyon

My 416 did the same thing. For me the fix was to clean the carb really good, take the top of the carb off is all I did, and changed the plugs and fuel filter. Then I ran seafoam in the tank. Ran like new after that.

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Jim_M

I've been lucky with my 416-H, never had a problem. I've owned two 520-H's that have had carb issues. Like Karl said a good cleaning and running Sea Foam in the gas was all it took to straighten them out.

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stevebo

There was a guy selling nos carbs on ebay a few months ago. IMO replace the carb and all your problems will go away. I tried cleaning mine on my 520 but could not get it right. I paid about $100 for the carb and worth every cent.

By all means try a good cleaning (which it sounds like you did) and if that isn't working then replace.. Good luck-

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markslawnmowerworld

We have alot of commercial eqiupment in our busy season....kawasaki engines,

on zero-turns....guys will complain about rough running engines....we keep sea foam on our shelfs in the shop just for this........really good stuff.

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Herbl

I have a 520-H also with the same problem and I also cleaned the carb or so I thought. After my first cleaning it was doing the exact same thing, surging and the choke would smooth it out. I'm into Classic Cars and one of my car friends is a Toro Tech and he told me what to do. Take the top of the carb off and use carb cleaner and squirt it down every hole you see, if you look down the ventura you can see 3 tiny holes above where the idle screw comes out, they are air bleed valves and they are tiny and they get clogged. Just keep squirting carb cleaner till you see it coming out of these 3 holes and your surging will be gone, I hope this helps it sure did me...

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nylyon

There is also a plug (on the 416 anyway) on the bowl in the front which when removed gives you a clean shot to the jet.

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MalMac

Thanks guys for all the help. Sounds like I have been on the right track. I just need to do it again. I have used Sea Foam in the past and yes it is good stuff. Well I am off to try all the suggestions. I'll be back to keep you posted and to ask more questions. This is why I joined RS. As long as I have been around Wheel Horses there is still alot of people that know more than I do that is willing to share thier knowlegde.

Tim

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