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Discussion Starter #1 (Edited)
I have an Ariens Deluxe 30 Sno-Thro Model 921032, four years old so sadly one year out of the warranty period. Had been running fine until recently. Now the engine turns over slowly after I get it started (I'm guessing 60-120 RPMs), and it won't get up to speed. After some minutes running, it engine speed increased, but not by much. At first I thought it might be the throttle control, but I did a compression test on the engine, and it came back at 40psi.

I had clean oil at the start of the season - and it's now quite black. I also see that oil is spitting out of the exhaust. There was more smoke than usual on start up, but not the clouds of smoke you would see with a blown head gasket.

I also heard a knocking sound when it was running.

So I'm guessing I have a significant problem - how do I go about diagnosing the issue so I can get it fixed?
 

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The knocking sound is disconcerting. The compression reading doesn't really worry me, the compression release will keep that number fairly low, at least with the pull start. I've gotten 35 psi with the pull starter, as I recall, with a Tecumseh that was running OK. With the electric start, you might get a higher reading (my engine does), perhaps the compression release is turning off at the higher speeds.

How is the oil level? Too high? Oil coming out the exhaust certainly doesn't seem good, there's no "normal" reason for that which comes to mind for me, at least.

I guess a small hole in the piston might be able to cause strange oil behavior, if the hole was small enough to still allow some compression. But that's probably a stretch. Does oil come out of the crankcase breather?

Checking your valve clearances wouldn't be too difficult, and could at least help explain a loss of power, if a valve isn't fully closing. But I don't think it would explain oil out of the exhaust, or a knocking sound. I'm assuming that if you move the throttle plate manually, you still get the same behavior. A weird governor problem wouldn't explain oil spraying and knocking, anyhow.

Pulling the cylinder head may be worthwhile, but hopefully others will have better suggestions.
 

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Discussion Starter #4 (Edited)
Ok, this is weird. Went outside to make a video of the issue to post on here, fired it up - and it ran just fine....

Can oil coming out of the exhaust occur when repeatedly pulling over by hand - which is what I was doing.

Oil level was fine when I last checked cold - I'll double check again.
 

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Can oil coming out of the exhaust occur when repeatedly pulling over by hand - which is what I was doing.
No. A whole bunch of pull-starting attempts on a healthy engine won't result in oil coming from the exhaust, without something else being wrong.
 

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Did you have the machine tipped up on the bucket? You can have had some oil run up into the cylinder and get out the exhaust.

Another thing you could do is removed the belts just to rule out any transmission issues. Those could causes noises, but not the oil problem.
 

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Discussion Starter #8
How heavy an oil are you using???
5W-30

Did you have the machine tipped up on the bucket? You can have had some oil run up into the cylinder and get out the exhaust.

Another thing you could do is removed the belts just to rule out any transmission issues. Those could causes noises, but not the oil problem.
Not since doing routine maintenance last year.

I should clarify - there wasn't visible (to the naked oil) spitting out of the muffler - but after a lot of pulling over, I noticed a fine spray / dropets of oil on the ground underneath the muffler, and on the body of the blower.

In other news, I did what I often do when in doubt about an issue - replaced the spark plug - it then fired up on first pull in minus 10 degree celcius weather from cold. I'll keep an eye on the oil to see if the spray is still there after running normally...

As for the knocking sound - I'm wondering if it is just an artefact caused by how slowly it was running before.
 

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Is the engine's crankcase breather in the area of the oil droplets? If it had a rubber breather tube, like a lot of the Tecumsehs, that could be a source of an oil spray.
 

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Discussion Starter #10
Well - it's back up to its old tricks. Ran great this morning when I wanted to clear a heavy snowfall. Then took it out to clear out the driveway from the plough truck...same problem as before. I guess it wasn't the spark plug

Here's a video showing what is going on. Any ideas?

 

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Does it accelerate if you press the primer bulb once it started? Try doing it to keep it from dying out. If it helps, you have a fuel delivery issue.
 

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do you have electric start?

If so, just wondering what the compression test would be using the electric start?

I would also do a cylinder leak test if you can.

Also take a look at the spark plug and inside the cylinder if you can.
 

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Almost sounds like the compression release is staying released.

A cylinder leak down test & compression test while spinning with the electric starter, would be my next test.

Broken valve spring is my wild ass guess.
 

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Try removing or at least loosening the gas cap. Maybe the vent is blocked. Your gas is not old and stale is it? I would also check valve clearances.
 

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I wondered about that too. I've had engines just barely struggle along, I think when they were WAY too rich, as I recall. Probably would be making black smoke. But it did make me wonder about something like that.

I would at least remove the carb cover, and look in the carb throat at the throttle plate and choke plate. Make sure they're doing what you expect.
 

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Discussion Starter #18
Almost sounds like the compression release is staying released.

A cylinder leak down test & compression test while spinning with the electric starter, would be my next test.

Broken valve spring is my wild ass guess.
Spoke to a local buddy - whose guess was a leaking valve cover. He suggested doing a short run with the OHV cover removed. Here's what happened. I'm no engine expert, but I'm guessing the spurting oil part way through isn't right...Any comments?

 

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I don't think it's a fuel issue as a too rich condition is usually black smoke. Just out of curiosity I'd check the valve clearances. These engines will run with extremely loose or tight clearances. I've seen them run with as much as a .017 gap. Perhaps the oil finger on the end of the rod has broken off and you haven't been getting full splash lubrication resulting in gradual wear of the valve guides and piston rings. It might be a broken piston ring, burned valves/guides or previously seized piston. For oil to come out the exhaust it has to get to the combustion chamber. It could be the crankcase vent is vacuuming oil into the carburetor and burning it off that way producing the white smoke and a very rich condition that makes the engine struggle to rev up. I have the feeling it will have to be torn down to find out and it will probably be very expensive if you choose to fix it.
 
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