# Possible Leaking Exhaust Valve - Need Advice!



## KATfishing (Dec 25, 2016)

Tecumseh Snow King 4-Cycle, Horizontal Crankshaft, Air-Cooled, Model 31AE5HTG799
Craftsman 9 hp 28" snow thrower, model 247.887900 made by MTD in 2007. 

At the beginning of the season it was starting rough and running rough. I replaced the 640349 fixed jet carb with a non-OEM fixed jet Everest carb. New NGK spark plug, fresh non-ethanol gas, with Seafoam added. It starts on one pull, runs great on full choke upon first starting, then as motor warms I turn a click at a time until fully open when machine is warm (about one minute total). It begins stuttering and running a bit rough in idle. Once augers turn, it still sputters but after running it for about 10 minutes under load, when auger is engaged, it begins to smooth out, but still sputters in idle. I had posted about this on another thread a month or so ago, but yesterday made a discovery... 

It was dark outside and I could for the first time see the glowing orange inside the bottom of the muffler, with occasional hint of a small light flame coming out of muffler. The muffler doesn't turn bright orange on the outside, but I could see how hot it was on the bottom holes of the inside... glowing orange. When I shut it off, I pulled the cord with throttle all the way down and it does seem to pull very smooth... classic of this Donyboy video at 2:29 




So now I'm suspecting a valve clearance problem or something of the sort, unless the carb is really just running that lean and it's starving for gas. Since this is not a diagnosis / repair I am comfortable doing myself, I could use some advice:
1) Is it ok to still run it for now? It does an excellent job at clearing snow and seems to run flawlessly when under a large load. What is the risk level of permanent damage by running it as is?
2) How big / expensive (ballpark) of a job should I expect this to be from a small engine repair shop?

Any/all thoughts and advice much appreciated!


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## AandPDan (Nov 18, 2014)

I'd be looking at the carb first. 

A couple of questions.

What RPM is the engine running at? 
Can you perform a compression test?
What color is the spark plug?

It won't likely permanently damage the engine. The valve may need to be replaced worst case and the seat ground.


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## JLawrence08648 (Jan 15, 2017)

Sounds like it. Flames come out into the muffler from the combustion chamber, which is where the explosion of gasoline takes place, piston, spark plug, valves, and if the exhaust valve is leaking it goes in to the muffler.

To fix it is not complicated but you need to buy some things, a suction cup lapper, valve grinding paste, maybe a new head gasket, and either build or buy a valve compressor.

You take the head off, take the small metal side plate off that covers the valve, install use the valve compressor to compress the valve so you are able to remove the valve key lock, it's in 2 pieces, two halves. Push the out slightly, put a little paste under the bottom slanted edge of the valve, put the lapper on the top of the valve head, and turn. You want to look and have a nice clean and same color and size edge all around without skipping on the underside of the valve on the slanted edge. Then you are done. Reverse the procedure. I would also do the intake valve.

Using non ethanol gas and adding a lead substitute to the gas will help for longevity. Lead is a lubricant. Newer equipment and cars have harden valves and seats.

Another thought, the valve seat could have lifted out. To fix that, push it back down and use a punch making indents around the valve to keep it there.

A compression gauge is $15 or so and is reliable to accurately tell you the compression. I can start and run engines at 40 lbs but it should be at least 50 if not 60-80. If the compression is low, remove the spark plug, put a tablespoon or two of oil in the spark plug hole and start the test again. If the compression rises 10 lbs or more, especially 20, the rings are leaking.


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## Jackmels (Feb 18, 2013)

Without Getting Overly Involved, You can First Remove the valve cover and breather. Using a large Screwdriver Compress the Valve spring and get a flat file between the Valve stem and Lifter. File Away until you get clearance. (You'll have to remove the 2 manifold screws and swing the carb out of the way.)


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## MrDman (Oct 18, 2014)

Well did it glow with your old carb on it?
If not I would say it's running lean.Start it up and leave the choke on at least one click.Then have a look at it.


Sent from my iPhone using Tapatalk


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## KATfishing (Dec 25, 2016)

Thank you for all the helpful tips so far! I don't know the RPMs when I noticed the glow, but it was running full throttle. I did pull the spark plug and it has some dry black residue on it, but it was dry and mostly white/tan... seemed normal. I don't recall ever seeing it glow with old carb, but part of the reason I noticed was that my headline bulb burnt out for the first time ever and it was particularly dark in the morning, so I was really able to see the glow by looking inside the muffler. I'll try 1/4 choke to see if there is any difference in regard to running lean. Would I be right in assuming that if glow goes away with choke that it's a lean condition from the carb and not exhaust valve? If so, should I just try running it 1/4 choke, since the carb is not adjustable? Maybe I should have bought OEM for $50 instead of the non-OEM for $17 - lol!


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## AandPDan (Nov 18, 2014)

It's not unusual for a carb to be lean, not nowadays with the EPA regs and all. 

Start with that. If you can perform a compression test you could do that too.

The plug doesn't sound bad.


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## JLawrence08648 (Jan 15, 2017)

You can buy adjustable carbs for $17 off Amazon. Buy one with an aluminium bowl.


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## RAYAR (Mar 7, 2015)

If you occasionally get flames shooting out of the muffler, then it's likely an exhaust valve clearance issue. When the the clearance diminishes, the exhaust valve begins to open too soon letting the combustion leak by and shooting out the muffler. This tends to happen more after the engine begins to warm up, the exhaust valve stem clearance diminishes as it warms up due to it expanding, thus decreasing the valve clearance. Here we're talking thousands of an inch clearances and it only takes a few thousands to cause this issue.
~Ray


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## RAYAR (Mar 7, 2015)

Jackmels said:


> Without Getting Overly Involved, You can First Remove the valve cover and breather. Using a large Screwdriver Compress the Valve spring and get a flat file between the Valve stem and Lifter. File Away until you get clearance. (You'll have to remove the 2 manifold screws and swing the carb out of the way.)


The problem I see with this method is some of the metal filings are most likely to get flushed into the crankcase and create another problem unless you can be certain to flush them all out before re-assembly.
~Ray


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## Jackmels (Feb 18, 2013)

Well Then, Use a Magnet before Replacing the Valve Cover.... Like I said, "Without getting too involved".


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## RedOctobyr (Mar 2, 2014)

Jackmels, this isn't meant to be critical or anything, I'm truly just curious: Have you tried using that method, compressing the spring, and filing the valve, in-position? 

I had to shorten my HMSK80 exhaust valve a few years ago. A coworker is a machinist, he helped me use a surface grinder to precisely take a few thousandths off the back of the valve. As I recall, he said the valve stem was hardened, and would therefore be difficult to file by hand. That's what makes me curious about doing it manually, especially with it still installed in the machine. 

KATfishing, before attempting anything somewhat drastic, measure your current valve clearance. You can get a set of feeler gauges for maybe $5, they will help you figure out if your valve clearances are correct, you just have to remove a little cover on the side of the engine. And if they're wrong, you'll need the feeler gauges to correctly shorten the valve(s). 

As far as measuring compression, a compression tester is an excellent tool. But these engines have compression releases, to make them easier to start. So you're partially measuring engine "health" (like whether the piston rings are worn), but you're also measuring how much the compression release is doing. This is, in part, a function of valve clearance. So if you valve clearance is too small, you may also read extra-low compression. But if you fix the valve clearance, you might help both issues (low compression, and glowing exhaust).


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## Jackmels (Feb 18, 2013)

I've Done this More than Once. An Associate showed me this method.


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## Toro-8-2-4 (Dec 28, 2013)

RedOctobyr said:


> J
> 
> I had to shorten my HMSK80 exhaust valve a few years ago. A coworker is a machinist, he helped me use a surface grinder to precisely take a few thousandths off the back of the valve. As I recall, he said the valve stem was hardened, and would therefore be difficult to file by hand. That's what makes me curious about doing it manually, especially with it still installed in the machine.
> 
> ...


Ditto on what he said!

It is easy to measure the valve clearance. That way you are not guessing. You know for sure if it is a problem and how much you have to remove. You should be able to find the clearance spec for your engine. It is usually around .006 to .010 or .008 to .012. 
Also because of compression release you need to make sure you at right at TDC or a few degrees after. Otherwise you may get a false measurement.

If you want to take some material off I would remove the valve and grind it or if you can have someone turn some off in a lathe. That would be ideal. But not everyone has that available. I have hand ground them on a bench grinder. You could try a file but if it as hard as the file, it won't work. Just measure where you are before you start and go slow and keep measuring it with a caliper.

Also with the head off make sure the valve guide and seat is not worn. If the valve clearance was zero and ran for some time it can do a number on the guide and seat. It can become out of round and the valve will float around and not always seal. If that is the case you may have to get an oversized valve and ream out the guide. If the Engine is not too old or unpopular you may get lucky and have parts available. I know Tecumseh had such parts available for many Snow Kings. Lastly you may have to lap the seat. Lots of You Tubes out there on how to do it.

Good Luck!


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## JayzAuto1 (Jul 25, 2016)

Hey Guys, at the risk of causing a Firestorm of hurt feelings, and barring any FEAR on any FRONTS, I'd like to make a few observations, that are of my own opinion. In the short time I've been on here, I've seen a whole array of skill levels on this forum. They range from single posters, looking for a quick down and dirty fix, to save their ailing snowblower, to all-out professionals, and up to the full on modification guys, that can't/won't leave anything alone and will make it better looking as well as performing. The common denominator seems to be all want to be involved in some way of repairing/rebuilding/modifying their machines. I Respect each and every Contributor that comes here to share. Along those same lines, are the availability of tooling to accomplish these tasks. While some of the methods may be questionable, certainly not text book and undoubtedly may cost more than said machine, I think most of respondents will convey what works for them, or they perceive to work for them. I sincerely doubt that that any advice is given with malicious or destructive intent. While some of the advice given is overkill, I can appreciate the effort involved, the willingness to share said advice and the pure ingenuity of solutions provided. Not to mention the overwhelming sense of satisfaction in devising a well thought out repair/procedure that comes with it's own sense of accomplishment, many times an improvement over factory designs.
With that said, there is usually more than one way to "skin this cat" as they say, and this thread puts many of these 'skinned cats' on display. Valve 'Jobs' being what they are, there is no question that lathes, valve grinders, machine shops and sterile 'operating rooms' are the correct way to accomplish a long lasting warranty-able repair. And without casting stones, I have certainly taken my share of short cuts, for various reasons. I, like many of youse, have my enemies, Time and his Evil Twin Brother, Money. I have also taken short cuts, simply for the sake of a learning experience. I learn more from my mistakes, than from my success'. Granted, I have a supply of junk that I can practice on (some customers, some of my own "Learning"), but all of it has value, in one form or another.
While it may be absurd to suggest a machinist hack a stretched valve in a Snow King, it may be equally unfeasible to suggest that Joey Bag-O-Donuts buy $200 worth of equipment to slap together an engine to finish out a season. There are quite a few considerations in determining ones skill level to affect such a repair, but the economics of the situation should also come into play. I'll throw in a wild card*.....Common Sense....Again, varying degrees of this commodity. But I would argue, that anyone attempting such a repair as a 'valve job', would have enough skill AND common sense to change the oil after said repair. It matters not if it's due for an oil change or not, any engine will benefit from clean oil after this surgery. Wait for it......It's COMMON SENSE. 
As many of these machines as I work on, I come here to view each of these experiences, help out when I can, and even this old dog has learned a few trix here. 
Now, to be Buy-Partisan, many will look to 'Upgrade' their bundles of Love, at the slightest hint of trouble. That advice is freely given here also, at times, Force-Fed, and for that crowd, I say 'Go For It'. It's your machine, do as you like. You, and only You, can determine it's value, your skill level, your tooling situation, the depth of your pockets, and your willingness to deal with problems as they arise. 
This is a very large Forum, with an incredible amount of information, Technical articles as well as First-Person accounts, some good, some bad, so it is advisable to use the resources available, ask questions where necessary, Post about the success (or Failure) of repairs, and realize that opinions are like Bum Holes.......Everybody's got one.
So FEAR not, LESS is more sometimes, on all FRONTS!!!!!

The Above rant is my opinion, I will not be held responsible for temper tantrums, aneurysms or marital disputes. Thanx for reading. God Bless and Good Night

Jay


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## scrappy (Dec 7, 2014)

I just got a head ache reading just part of that:facepalm_zpsdj194qh


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## Jackmels (Feb 18, 2013)

*File Method*

Here's Results of the File Method, Feeler Gauge between Lifter and Valve Showing Clearance to Show the Method Does Work without Pulling the Head and Valve. Not a Complete Valve Job by any Means, but Clearance is Now Present. I would not Suggest this Method if You are Worried about Filings, or Want to do a Complete Valve Job. However, if you are looking for an Alternative Way to get Valve Clearance, it might be worth a try.


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## cranman (Jan 23, 2016)

Thanks for that Jackmels.....sometimes I just feel like a fix that isn't too involved! Whenever I pop a head I check the valves, but seldom do they need lapping. I did a 8 hp Briggs on a Toro that needed clearance added last year, and I wish I had known of this fix!


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## Bigbmn (Feb 11, 2017)

I too was a bit intimidated by this. The most difficult part was taking off the muffler bolts and carb bolts. I used a vice grip on both, and broke one exhaust bolt about half way. When the muffler came off, I was able to get a vice grip on it and turned it in a bit in then out then in then out, taking my time to work the bolt out. Hopefully u get the idea. A bit of of Penetration spray for rusty bolts too. Taking off the cover for the valves was easy, but after I took off the head, the exhaust valve was clearly not seated. There is a utube video of taking out the valve by using the tool that takes off Auto body panels. Took it out, ground it down and checked clearance at .004 to .008 for my engine. Needed to get all the gaskets to put it all back again


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