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Sears Onan Questions


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#1 glgrumpy OFFLINE  

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Posted May 19, 2014 - 12:09 PM

Bought SS 16 with Onan. Ran it at show, sounded like needed a plug with on/off running one cylinder. Got it home, new batt, started, ran about same. More time and it would fire a little, quit, fire, etc. Then once in awhile would backfire pretty big bang. Engine seems some noisy when running. NOW, thinking maybe the valve seat is loose and sometimes sets and runs right, other times falls out and valve is caught open, backfire. NOW, won't run at all. Gonna look at points next, but have to almost tear down engine to get in there and work! Think someone has been in before, finding some loose bolts and filter was out of it, and little things like they messed with it and put back w/out fixing. What think? Can a seat be replaces w/out tearing engine all the way down? My new Joy Toy is a dissapointment now with these issues. Just my kinda luck!



#2 TAHOE OFFLINE  

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Posted May 19, 2014 - 01:11 PM

Well that sucks for you.

I haven't one open, but I'm pretty sure head can be easily pulled and vlave replaced or repaired.

it could also be the coil, one side has went bad.

They have issues also the air intake leaking.

Check plunger for the points? maybe hanging up?

Sure does sounds like a valve/valve seat though from what you are saying, runnig then backfire then running then not.


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#3 TomLGT195 OFFLINE  

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Posted May 19, 2014 - 03:39 PM

My onan , long gone, was acting similar. it was electrical. but it wasn't making a lot of noise just running crappy with the back fire. good luck.    Tom


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#4 olcowhand ONLINE  

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Posted May 19, 2014 - 04:01 PM

I've never seen a valve seat come loose in an Onan, but I'm not saying it can't happen.  Could be a lot of things, but may just be a sticking valve, or as said, an ignition problem.  I've had a few SS16 tractors and they are great units!


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#5 JDBrian OFFLINE  

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Posted May 19, 2014 - 04:28 PM

If it's always the same cylinder that's missing then it could be the coil for that side. I'd also give the points a quick check. Pitted or out of adjustment points will make an engine do some strange things. I've had an engine run poorly then suddenly quit. The problem was the points. You have a marginal spark and then at some point it just doesn't have enough for combustion. 


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#6 olcowhand ONLINE  

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Posted May 19, 2014 - 05:13 PM

If it's always the same cylinder, then swap wires at the coil.  If the miss follows to the other cylinder, then it's either the coil or the plug wire.


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#7 glgrumpy OFFLINE  

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Posted May 19, 2014 - 05:31 PM

OK, update:  Did you know engines need "fuel" to run?  I put some gas in tank in back, tractor is lifted on stands in front and wasn't getting gas. Last time it just ran out. Today I sprayed starter fluid in to try and took right off. SO, more gas in tank and then it caught. I hate "Dumb-asses" working on my stuff....hee, hee!   Anyway, starts with choke, idles pretty good, but acts like way rich when throttling. Still hit/miss even with new plugs. I did take off the hood, grill and muffler to get at the darn thing. Pulled points cover and filed some and they looked good and plunger looked fine. One carb set screw does nothing to change, and other one has to be out too far I think to make it run at all. SO, ordered carb kit for it and also new plug wires. My wires were taped in one spot and anothr spot rubbed hard and they look orig as in OLD. Most shops in my area have NO onan parts and won't sell because they have to pay retail prices and still raise them to profit. 3 places told me this. One has source from Ohio somewhere and he has this stuff on order now.  JD dealer wanted exact part numbers to order and no other way, sheesh!  Put the drive belt on and was PIA, having to loosen both idlers to get belt around the guards that hold them on when loose. Right now seems kinda tight and not releasing well with pedal. I can still move one idler some to adjust, but will do later when wheels back on tractor. Don't really think any valve issues afterall and am happy for that.


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#8 MH81 OFFLINE  

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Posted May 19, 2014 - 05:38 PM

The choke on to run symptom can be indicative of what Marty was talking about with the bad intake gasket.

The intake is a two piece tube and the gasket can fail, allowing more air.

#9 glgrumpy OFFLINE  

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Posted May 19, 2014 - 05:50 PM

I was told about that intake from my buddy. His was leaking. Visually looked ok, but guess I could use spray or LP to see it it draws in somewhere? Gasket? Can I just Silicone what is on there now and will hold? Maybe I'll pull of when get carb kit. BUT, then won't have gaskets and need another big wait for those to come in. 



#10 TAHOE OFFLINE  

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Posted May 20, 2014 - 08:16 AM

Glad it wasn't a valve or seat.

 

I would say since the fuel screw didn't change anything, you need a good carb cleaning, sounds like you got a plugged port.

On the intake, they are just "glued" together and can be split apart. Many guys will drill out the little bosses around the perimeter and put some nuts/bolts to hold it together. Just use some good gas impermeable RTV as a sealant.

 

I am hearing guys using a Harley Davidson dual coil to replace the stock Onan, much cheaper and works just as good.

Imagine that, a HD part actually cheaper than the part you need.


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#11 boss351c OFFLINE  

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Posted May 20, 2014 - 08:38 AM

Do yourself a favor and change the condenser while you are at it.  Mine (CCKA in a Case 646) started running like crap, missing, wouldn't rev up, kept stalling out, would clear up for a few seconds, then do it all over again.  Was just a bad condenser, changed it out and it purrs like a kitten again.  Now I just need someone to buy it!


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#12 glgrumpy OFFLINE  

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Posted May 20, 2014 - 09:02 PM

Boss how about a picture and price on that 646. I see you in Michigan, how far up?


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#13 boss351c OFFLINE  

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Posted May 21, 2014 - 08:14 AM

I am just selling the Onan engine, not the tractor.  I just finished an engine swap to a Kubota diesel in the Case.  I am up in Midland (48640).



#14 glgrumpy OFFLINE  

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Posted June 07, 2014 - 08:05 PM

Well, got carb kit, the right needle and new plug wires. Runs just like before. We examined the intake and didn't find any splitting on it. SO, NOW, gonna try a points/condensor set!  Someone buy this thing from me, been PIA, hard to work on and find parts. Should have left it there at swap meet I guess! :wallbanging:



#15 MH81 OFFLINE  

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Posted June 07, 2014 - 08:16 PM

Sorry GL.  

I was hoping you would get it with a carb kit.

It still sounds like its sucking air to me, but the points & condenser would be worth it.

 

No Chance one of the wires are loose in the top of the coil?






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