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Onan problems


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#1 JD DANNELS OFFLINE  

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Posted June 20, 2015 - 04:35 PM

Was mowing yesterday, shut down to empty bagged. When started it had dropped a cylinder.
Took the heads off this afternoon. No holed pistons and no burnt valves.
But I am pretty sure the intake valve seat is not suppose to go up and down with the valve.
Will finish taking it down Monday.
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#2 KennyP ONLINE  

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Posted June 20, 2015 - 05:21 PM

That just may be the issue!


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#3 Alc ONLINE  

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Posted June 20, 2015 - 06:11 PM

Sorry to hear this ,is this something that can be repaired ?
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#4 Littledeere ONLINE  

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Posted June 20, 2015 - 06:33 PM

That sounds like a P series Onan there the worst for this


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#5 JD DANNELS OFFLINE  

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Posted June 20, 2015 - 07:33 PM

Sorry to hear this ,is this something that can be repaired ?

I think so. After posting this I have been out on the Net researching this. This seems to be a fairly common problem with these. The seat was sticking to the valve due to oil adhesion.
They do make oversize seats, but the block needs to be machined to fit them.
I will have to check with a machine shop to see how far down I have to tear the engine.
If someone does not make a pilot to fit the valve guides(like they used to on overhead valve car heads) and a reamer to do this in the frame they sure should!
I really should do a complete rebuild, if I have to tear too much out to get it fixed, but had hoped to do that next winter since I can not really afford it right now.

I should have torn it down sooner, it has been blowing oil. Pretty heavily for a couple weeks.
With the loose seat apparently the compression was bleeding into the crankcase.

Edited by JD DANNELS, June 20, 2015 - 07:43 PM.

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#6 tyler OFFLINE  

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Posted June 21, 2015 - 06:00 AM

check plug wires and spark plugs. I had same problem, where the boot meets the spark plug it was arcing.  



#7 MH81 ONLINE  

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Posted June 21, 2015 - 06:21 AM

There was a trick on the Briggs with the seat issue to take a center punch and just slightly swell the wall where the seat goes, lightly rough up the outside of the seat and then JB Weld it back into place.
Had to do this with Dads mid 80's craftsman

Of course, if we had spent the >$200 for he muffler when it failed, the seat wouldn't have cooled to fast due to the pepper shaker mufflers.
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#8 olcowhand OFFLINE  

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Posted June 21, 2015 - 07:15 AM

I've peened many seats back in tight and never had any come loose again. This works fine unless the seat's hole has been wallowed out.
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#9 JD DANNELS OFFLINE  

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Posted June 21, 2015 - 10:04 AM

There was a trick on the Briggs with the seat issue to take a center punch and just slightly swell the wall where the seat goes, lightly rough up the outside of the seat and then JB Weld it back into place.
Had to do this with Dads mid 80's craftsman
Of course, if we had spent the >$200 for he muffler when it failed, the seat wouldn't have cooled to fast due to the pepper shaker mufflers.


When I get the valve out I will see if it is tight enough to peen the seat. Had heard of doing that but had never done it.
Any idea how much wear would be tolerable? I imagine I can check it with a feeler guage?

#10 JD DANNELS OFFLINE  

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Posted June 24, 2015 - 12:04 PM

Update on this engine. I got it torn down and found that the seat pocket was not pounded out.
I have been out on the net looking for a solution.
Some said they had used JB Weld, but there was a lot of debate as whether it would hold up to combustion chamber temperatures. My dad said he knew it would not hold in a diesel. he had tried it in that Head busting International crawler he used to have.
One guy said a Briggs factory tech recommended Super Seal by the Silver Seal Corporation.
I looked up the specs and it is suppose to stand 3,000 degree temps. The only drawback is it is about $40 for 2 oz.
I am checking this afternoon to see if NAPA has it.
My intent is to glue it back in with that and then peen the seat.

Edited by JD DANNELS, June 24, 2015 - 12:07 PM.





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