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cleat

My dreaded Onan surge and it's cure

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cleat

Well, I got the dreaded surge about a month ago.

Happened around 1/2 way through mowing my 2 acre lawn.

 

Finished mowing with the choke partly on then pulled machine into shop and cleaned carb while it was still bolted onto intake (it looked very clean inside with nothing plugged that I could see).

 

Well, a couple of weeks ago I was mowing the back part and it started again so I finished with the choke partly on.

Another thing I should mention is that before the surging starts there is a noticable loss of power with the machine working the governor very hard for little to no reason.

 

Well a couple of days ago I pulled the carb right off and disassembled it.

Again, it looked very clean.

 

Blew it out then I heard a noise.

Welch plug blew out. I was holding the blow gun a ways away from the carb too so I don't believe that I should have blown it out

 

Reassembled carb (after I finally found the welch plug on the shop floor) and sealed up welch plug.

 

I just now came in after mowing the entire yard with absolutely no issues.

Tractor seems to have more power than it ever has.

 

Even used less gas, less than 1/2 tank to do 2 acres and it was thick heavy partly wet also.

 

I believe that welch plug could have been sitting in there loose the whole time.

 

Whatever the cause was, I am happy now.

 

This was my 520HC.

 

Cleat

 

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posifour11

Good deal!

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FatJackDurham

Welch plug?

 

I saw somewhere that the intake manifold develops cracks along the seam.

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Pollack Pete

On the 4 or 5 Onan powered equipment that I have,I use nothing but ethanol free gas and I load it up with Sea-Foam.Mater of fact,I use ethanol free in all my small engines.Our friends,the government are supposed to be using 10% or less ethanol.A friend of mine who is a member of the New York State Gasoline Retailers Association tells me that our gas usually has 20 %ethanol.Imagine that...……..the government could be telling a little lie.

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WHX??

interesting Cleat, since running the choke partly on one can assume it was running lean or air going by the loose plug? Where was the plug located?

iplimage.png

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cleat

It is a small little plug located just above the idle jet.

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posifour11
41 minutes ago, cleat said:

It is a small little plug located just above the idle jet.

You may have saved my late father's ss/16. That makes total sense!

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Cee245

@cleat,

Can you show us pictures and how did you get the Welch plug to properly seal?

I have a P216 and it's developed a surge that I haven't figured out yet.

 

Thanks Cory 

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lynnmor

A welch plug is a one time use part.  Clean the bore where it goes, then apply a small amount of fuel resistant sealant to the edge of a new plug and place it in the bore.  Now take a punch and hammer and gently tap on the dome of the plug till it tightens in the bore.  It doesn't take much and you should still have some dome shape when done.  Hopefully you can find new plugs at an auto parts store.  Measure the bore, I believe it is 3/8".

 

Onan doesn't include the welch plug in their kits, but some cheap Chinese kits have them. :bitch:

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gwest_ca

If the plug is tight and you want to seal it on the outside clean well. Get some nail polish your wife no longer cares for and apply a couple of coats to the edge of the cup. If it has some color it helps to see if your application is complete.

 

Seal-All is another product that will withstand gasoline but I would not want to use it if installing a new plug. Too much chance of using too much and causing internal problems.

 

Garry

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