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Discussion Starter #1
Hi all, New to the forums.

I just scored an Ariens 8526 for free and am having some trouble getting it to run right. It did run before I started tinkering with it, and it does run better now, but not much better. It's got a Tecumseh LH318SA on it.

It was dirty. I mean really dirty. I took all the shrouds/covers/brackets of and removed all the grime. I emptied about 1/4" of sludge out of the gas tank, rinsed several times and dried thoroughly. All new fuel lines and a fuel filter were added during re-assembly.

The carb so dirty I couldn't even see the idle speed or mixture adjustments. I was originally going to rebuilt it, but realized that a new one was only $8 more than a rebuild kit. Guess which one I bought. I followed the Tecumseh technicians manual and set the main and idle screws to 1.5 and 1 turn respectively.

After getting it all back together, adding fresh premium fuel (with stabil) and putting in a new spark plug I primed it and pulled the cord. It started, but the idle was very poor and after a few seconds died. I repeated this a few times and eventually got it to stay running, although still rough. The weird thing is adjusting the idle screw didn't really seem to do anything, but adjusting the main did. It leveled right out and only had a mild "snort". At full throttle it seems to run better but still does have that "snort". Is this normal? It hasn't snowed yet here in NH so I have no way of testing under load. Also, restarting it either hot or cold it requires a few pumps of the primer bulb and maybe even more pulls of the rope.

I did measure compression cold and hot: 75 and 90 psi. I know this model has a decompression feature but I don't know what is good or bad for hot or cold compression figures. I've read anything from 50 to 100 for cold, no info for hot. I didn't really think this was an issue, but I went ahead and de-carbed it with some seafoam thinking maybe a stuck ring. I don't think it helped a bit. Could it be a valve issue? I haven't pulled the head yet and don't really want to unless otherwise influenced.

I suppose my only reason for posting here is because I have a newer Ariens 624 with a Tecumseh OH195SA that runs like a top every time. Choke, a few primes and even well below 0 it will start on first pull. For comparison I measured the compression, 160psi, although i don't believe this engine has the decompression feature.

So what do the experts think?

Thanks in advance for any and all help, and stay warm!
 

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Not an expert, but it sounds as though your idle jets, on the side of your carb are not completely clear.
 

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Discussion Starter #3
Thanks for the reply.

The carb is brand new, was set to the factor specs and was adjusted both "rich and lean". It responded to the main jet more than the idle, but neither adjustment eliminated the issue which is what led me to think it was something else. I guess it could be a bad carb. Maybe cleaning the original isn't a bad idea after all.

Does anyone know what the compression should be cold?
 

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Well the snort you describe, sounds it might be a over rich situation. What does the plug look like?

On another note, what did the oil look like when you drained it? Is there a chance that it was ran with low oil, considering the level neglect that you have already corrected?
 

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Discussion Starter #5
The new plug looked good, gray without any oil. I forgot to check the old plug.

The oil looked like it had a seasons worth of running. It wasn't brand new, but it definitely wasn't black or sludge. There was plenty of it too, right up to the line on the dipstick. I guess it's possible it was run low at some point, but I have no way of knowing.

The fact that it runs worse at idle doesn't worry me too much. As long as I can get it started in the winter and move some snow I'll be happy. I'm just worried there is actually something wrong with it and applying a load may cause damage.
 

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Is the SNORT coming from the carb or the muffler? Older engines have a tendency for the valves to wear into their seats and losing their required clearance. The snort is usually heard when the engine is at operating temperature causing the exhaust valve to lengthen and lose the .008 clearance required to keep the valve seated and emitted through the muffler.
The compression readings you have do not show a valve problem when the engine is cold. Could be a valve or just a little tweaking of the carb to eliminate the snort. :confused:
 

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Discussion Starter #8
Now, that I didn't check initially. It appears to be coming from the exhaust though. In the right light I can actually see it. I'm thinking I just go ahead and the pull the head and valve cover to check. With any luck I'll report back tomorrow.

Thanks again for the help.
 

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Might check the valve to tappet clearance. Located through the access panel/PCV port on the side of the engine.
 

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Discussion Starter #10
So I pulled the Head and valve access cover after work today. Measuring the valve clearance revealed ~0.004" for the intake side and nothing for the exhaust side. I have read that the exhaust side is more prone to this than the intake side, although I'm not sure why. Is this what they refer to as worn valve seats? I don't see any issues with the cylinder. please let me know if you disagree.

So do I just remove the valves and hit them with a file to bring the gaps back to spec? Speaking of, I'm fairly certain the manual mentions 0.008" and 0.012", although I could be wrong. I do have a grinder and a lathe but I think both may be overkill for this.

Also, it seems that everything just exposed to light is rather dirty. Should it be? Should I clean it prior to putting the head back on?

Thanks again for all of your help!


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As long as you have the head off, you may as well remove the carbon build up. I use a brass wire brush and a little Seafoam to remove the carbon.

The high heat from combustion causes the valve face and seat to shrink and eliminate the required clearance. The valve stem expands from the heat and will keep the exhaust valve from seating when at operating temp. A compression test on a hot engine would have shown a large decrease in compression because of the unseated exhaust valve and also cause the snort you described.
Besides grinding the valve stems, you should lap the valves to insure a good seal. This will require time and patience if you do it without removing the camshaft and lifters.
You will have to remove the valve, grind a "little" off the stem, lap the valve, check clearance, grind a "little off the stem, lap the valve, check clearance and so on until you reach the .008 - .012 clearance. Be very careful with the grinding, if you take off to much, you will need a new valve and have to start the process all over.

You might get lucky with using the old head gasket, but would be wiser to just replace it and torque it to specs in the correct sequence. (found in the service manual). Head gasket part number 34041A.

I hope this helps.
 

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Discussion Starter #12
I will do just that. Is the current carbon buildup from running too rich, from bad gas, etc.? I'm religious about using fresh premium gas and adding stabil/seafoam to keep it fresh. I'm hoping this will prevent the carbon buildup in the future.

"A compression test on a hot engine would have shown a large decrease in compression because of the unseated exhaust valve and also cause the snort you described." This makes sense in my head, but my hot compression was better than cold. Or are you referring to what could be possible while hot compared to cold?

Lapping the valves. Is this just done with a lapping compound where the valves seat?

As for the grinding I can always just indicate on the lathe and take the required amount off, although I'm not sure how much is required on the exhaust side as it's fully closed. I suppose I could start low and just keep going up.

My local shop has a gasket in stock, I'll be picking one up Saturday AM. It's part # 36448 though, not the one you references below. Is this just a replacement?

Great info here. Thanks a bunch.
 

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I would say that is normal carbon build up from engine oil carbonizing.

Yes the valve clearance would decrease to the point of holding the valve open the warmer the engine becomes and eventually would lead to lower compression and snorting.

Valve lapping requires a lapping tool (wood handle with a suction cup on each end) and lapping compound applied to the valve face and seat.
Since you have zero clearance now, you could start with removing around .008? now and checking the clearance as the lapping proceeds. You want an even shine on both the valve face and seat.


I took a guess on the head gasket since I do not know the complete model and spec numbers for your engine – SORRY. :eek:

 

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Discussion Starter #14
Sorry everyone, I've been super busy and haven't had a chance to work on much of anything. Last week I turned down the valves and Monday night I cleaned everything and finally got it all put back together with a new head gasket. I did follow the technicians manual I found online and torqued the bolts down in 50 in-lb increments to 200 in-lbs. All said and done, the intake and exhaust clearances were 0.008" and 0.013", it was a tight 0.013" too.

I reset the carb setting per the manual (1 turn on idle, 1.5 turns on high), primed the bulb twice and it started on the first pull. It definitely runs better, but again, not like the newer smaller Ariens I have. Similar to before, it seems to run better at full throttle, especially after I richened up the main screw. At idle it still seems to hiccup and surge a little, no matter how the mixture screw is set, other than closed. Warm though, it still takes 5-6 pulls to get it started again without the choke or primer bulb.

Now the interesting part. Tonight I checked the compression cold and it actually went down to between 65-70psi! Before it was 75+. I have yet to check it warm though.

Any other thoughts as to diagnosing this, or should I just live with it and wait for the snow to start falling?

Thanks again for everyone's advice.
 

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Lower compression might be good. If you look up some videos for lawn tractor starting problems with Briggs OHV engines you will find out that as the valves get loose it makes the automatic decompression thing stop working. This in turn causes the engines to be very hard to start and causes extra wear on the battery, starter and solenoids. It mimics symptoms of a dead battery.

Basically what happens on those engines is the valves get so loose that when the decompression device opens instead of opening the exhaust valve slightly like it is suppose to do it just takes some of the slack out of the pushrod.
 

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Discussion Starter #16
So the cold compression should not be a reason to worry? I've heard others say that 90-100 is ideal even with the compression release. This is my reason for asking.
 

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I have heard some can be as low as 50 and still be good. Briggs says to check compression turn the crankshaft backwards and see if it rebounds.
 

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I recently did a valve job on a 5 hp Tecumseh that originally had 30 psi compression. After the valve job, it had 55 psi compression and starts and runs great. I have always used the 90-100 psi compression reading for diagnosing small two stroke trimmer type engines.
 

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Discussion Starter #19
So I guess I can stop worrying about the compression value. I'm still wondering though why starting be so troublesome, especially with a warm engine?
 
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