Is the 632334A carb adjustable, or is it an exact copy of the original (non-adjustable) one found on the EPA HMSK80 engine? I'm hoping it will be adjustable, and thus an improvement on the original part. I too have the lean hunting problem.

Thanks,
Brad

Yes, it is adjustable. I had to adjust the governor down after installing it.

I too have the surging on my blower. I have the 640052, AKA 640349 Tec carb. Is this a pre EPA carb? It appears to be adjustable but I have a hole that is threaded but nothing occupies this hole, so I believe I am missing a piece. The only way to keep it running to to run it wide open and set the choke aggressively. It does seem to run well under load however. Will the 632334A work on my blower? You are all more knowledgable than I, so any help would be appreciated.

If yours has the same center bottom brass bolt like the one in the picture at the top of this thread, then it is the non-adjustable type.

The 632334A will fit any of the L-head 8-10 hp engines.

I have this snow blower since 2001 and started having problems with surging since end of last year. Last week i read this forum and removed and cleaned the fixed mixture screw. upon restarting had less surging but still some. i then removed the screw but this time i used these gas oriface cleaning tool i have and i found build up of contaiminates in the small oriface that is on the but end. upon restarting the engine runs like new. i then bought a gas shutoff valve and installed a small clear filter after the shutoff i hope by running the gas out of the carb it will be more reliable. i always use stabilizer but this alcohol gas is bad................

GREAT WEBSITE!

Excellent. I had the same problem with my snowblower. Googled the problem and ended up here. I bought a 632334A carb from Pat's Small Engine Parts. It took 15mins to swap out and no more surging!

Thanks alot folks! I will post a follow-up if anything changes. $70.00 is alot better than spend $1000.00.

so after a successful winter season of snow blowing I have found that the fixed mixture screw is the surge issue with the HMSK80 ariens snow thrower.....after this was cleaned in december 2007 with a gas orifice cleaning tool this engine now runs better than new....and at the cost of zero..... this is a great internet web site...thanks to all especially those excellant pictures...happy snow blowing to all...

Great info here !! Had the same problem on my HMSK80,pulled off the bowl (which was clean) and backed out the upper needle and blew carb cleaner through the hole until it came out the bottom of carb consistantly.Then I cleaned the center brass fitting (adjustable) and cleaned out the small hole between the threads with a pinvise drill,think it was about .073,made sure everything was clean on reassembly,set upper needle 1 turn out and bottom screw 1 1/2 turns out and no more surge !!!!
Wanted to tackle this today as we're supposed to get snow tomorrow here in SE Michigan........
Thanks for the cool page.

See how nice engines run when the carbs are adjustable...........in 20 seconds you can make a problem go away,instead of buying a new carb.............or racking your brains trying to figure whats wrong.........

I'm new to small engines...

I have a 8.5hp 28" craftsman snowblower. Bought it used last weekend. When the weather was warm it surged pretty badly. I attempted to adjust the carb yesterday and it was freezing. It would start OK but would cut out when i tried to slowly turn the choke off. I don't know much about carbs but reading here it sounds like i need to take it off at a minimum and clean it..or possibly rebuild it. My carb looks just like the ones pictured above except that the one screw in the bottom middle of the bowl is smaller and has a spring around the screw. I tried fiddling with both that screw and the one in the top middle of the carb with no luck.

So some stupid questions. I am somewhat mechanicly inclined. How do i drain the gas? Just tip it over and pop the gas tank cap and let it drain into a bucket? Or can i remove the little black hose that runs to the carb and let it drain out that hose? Does that hose just slip on? Does anyone know of a website that gives the basics of rebuilding or working on a carb (the closer to this type the better). Also i'm a bit confused about the pre epa carb and the post epa carb....is the carb pictured above adjustable at all? The numbers off my engine are
143.978001 and 6247r.

I looked into getting it tuned up and of course they are 4 weeks behind. Saving nickles and dimes we were only able to buy last weekend. Any suggestions greatly appreciated as we are expecting snow. Thanks! RC

If the fuel is much over a month old, I would replace it for starters. If it isn't easy to drain out of the bottom of the tank, remove the bowl nut/ bowl and catch it in a pan. You could just try a simple quick clean , which can be done w/ the carb on. Clean the bowl and the 2 small holes in the main jet (bowl nut)with tiny wire like a bread tie. If you have some spray carb cleaner, blow through the holes in the jet and up into the fuel pipe above the jet in the carb. Run a little fresh gas through the line and carb before you reinstall the bowl and nut. You can also remove the side jet and spray cleaner in there. Count the turns in before removing. It's quick, cheap, many times effective and easy. Turn the bottom screw out for a richer high speed adjustment. A bit of carb cleaner in the fuel will help clean further as it runs. If you don't get the results you needed, it may need further service. Any signs of water sitting in it, such as corrosion is bad on these and won't come out w/ cleaner .

I'd dare say that without knowing this carb in and out that there is a vacuum leak somewhere. Easiest things to fix with new gaskets. Try running with engine at surging speeds and spray some carb cleaner "lightly" around any gasketed/tubed connections if engine revs and holds steady there is a crack etc in some fitting disassembly required to find culprit

Thanks for the replies thus far.

So to clarify...on the carbs pictured above, where are the adjustments? My carb looks almost identical to the one above except that the one nut in the bottom center of the bowl does look different than the one above. It is a small bolt looking thing with a spring around it. Also appears to be an adjustment on the top via a hex key. Is this correct?

Also, is there a "starting point" for these adjustments? I'm off to try and dig up some general info on carburetors

thanks
RC

On yours, the bottom screw is the adjustable main jet. The above series is not adjustable. The other adjustment would be a slotted screw just above the bowl, on the out facing side of the carb. The small hex screw is typically the base idle. Here's the manual.

Here is a link that might be useful: Tec 4cycle manual pdf

Thanks to everyone who has posted into. Tomplum, thanks for the link. Things are looking up a bit. I spent an hour outside in the dark with a headlamp taking the carb off the blower.

Disassembled it as far as i felt comfortable and cleaned it as best i could with carb cleaner. Ok several more questions...

On the carb it has a number 1132H64. I am trying to determine what "series" it is in the pdf that tomplum so kindly posted. I think it is a series 3 as it has the bosses on each side of the idle mixture screw and only has one screw holding the throtle plate as shown on page 15 of the pdf. Is there a way to double check the "series" with the number 1132h64? If i were to get a rebuild kit what would i need to look for?

Also. I have never worked on a carb other than occasionally adjusting the carb on my folks old tractor. In taking this carb apart i found a tiny bb in the bowl. It doesn't seem to me that it should be kicking around in the bowl. Looking at the main adjustment screw in the bottom of the bowl it appears that the "bb" fits in there perfectly. In looking at the PDF i can't find the "bb" in any of the figures. Any ideas?

Anyhow i'm off to bed. Hopefully i'll figure out what the bb is and where it goes and get the carb back on tomorrow after work. I'll likely buy a rebuild kit as the gaskets and o rings look like they have seen better days...any links?

Thanks
RC

I'm guessing the bb maybe a casting plug? Look, with the carb inverted, at the stem where the bowl nut threaded into. On the side of that stem many times where a passage was drilled, has a bb plug. That isn't meant to come out. One would have to peen in carefully back in and hope for the best. One has to be careful on these carbs. Guys that do it all the time just know what to watch for. IE some versions can be ruined installed the jet on the side with the carb inverted and care that little sleeve didn't work its way up during the cleaning process. Some had fuel pipes that were also suggested changed that doesn't come with the kit. None of it is hard, just like anything else.
I would review the carb section of the manual. Verify that the float is empty and that you feel confident on the bb. If there are signs of corrosion, with everything else- I would replace the carb. I assume that you have a Tecumseh dealer near by. If not, I will list a parts look up link and you can let Google do the rest. Tec look up online uses the spec # after the model #. Good luck.

Here is a link that might be useful: Tec parts

Better....then worse...

I got the carb all put back together and re-installed. The blower started right up and i made some minor adjustments to the carb. Then i shut the blower off and attempted to re-start it. Nothing. It doesn't seem like the engine will turn over. I hit the electric start and it obviously didn't sound right...so i grabbed the pull handle and it would only come out 3 or so inches and then hit major resistance. Any ideas?

I looked at the tecumseh manual posted above and couldn't find any troubleshooting that pertained. I bought the unit used and it did not come with an owners manual....

thanks
RC

I hate that! No history can bite sometimes. Oil in engine? Auger not engaged somehow? Remove the spark plug- cranks now? Beyond that, one has to pull either the pto cover or engine blower housing and check for something physically keeping the engine from turning. Maybe e starter binding? That way you can verify if it is something internal or not. At the edge of our seats....

Yes oil in the engine. I was planning on changing once we get some decent weather. I have been working on it in the dark with a headlamp as i don't have a garage.

I removed the spark plug and still no crank. I'm afraid to hit the electric start as it makes an obviously bad noise. The starter rope still only comes out 3 or so inches.

ugh. it seemed to run great after i got the carb on.

How do i check if the e starter is binding? I didn't see anything in the pdf regarding the e starter. What do you mean "auger not engaged somehow?" Do you mean make sure that the auger isn't on (i.e. would throw snow if running?). The lever for the auger is up (the auger should be off). "pto cover or engine blower housing" not quite sure what you mean.

what a pain. i have nowhere to work on this beast except outside in the dark after work in the snow. it may have to wait until the weekend...meanwhile it is snowing...

thanks for all the help
RC

To check for the e starter binding, I would pull the engine blower housing first. That is the housing to which the pull starter is mounted. That way you can tell if the starter gear is still engaged in the flywheel ring gear. If so, the slightest amount of lube carefully placed on the shaft is all you want. If it is rusted badly , you will need to R&R the e starter to correct. Turn the engine by the flywheel -rocking it backwards /forwards and hopefully the gear will retract. You may have to loosen the starter. In fact, if you felt it easier, you could pull the e starter instead of the recoil blower housing. Generally, it is easier to remove the fuel tank first and then the starter if need be.
If all checks out there, then you will need to confirm that nothing is holding it on the PTO side of the engine.

Starting problem solved!

This evening i worked on fixing the starting problem. First i tarped the snowblower and set up a lantern under the tarp. I was hoping that some water had frozen somewhere and that was preventing the pull cord from moving. No such luck.

I then started looking at the housing seeing how i would take it off this weekend (getting sick of working at night with a headlamp). Taped on the starter motor thinking that could free something up. Nothing. Looked at how the starter motor is removed.....What? No bolts? Huh? I grabbed the starter motor and jiggled it...sure enough the motor moved significantly....the bolts that mount the starter to the engine obviously vibrated loose and the starter shifted binding up the flywheel.

Now i just have to look in the parts manual and figure out what size bolts hold the starter on. Anyhow i'm relieved. I was worried that it was something major.

Thanks again to everyone who has posted ideas. Especially Tomplum.

On a different note. Tom - you mentioned that the "bb" could be a plug on the side of the stem of the carb. On page 18 of the PDF manual it shows a "ball plug" in figure 33 on the side of the stem....it says "do not remove any ball or cup plugs". The bb i found in the bowl fits pretty good in a hole that is in the same spot on the stem of my carb. Any ideas what the hole does and why it is plugged. Is the bb supposed to fit in the whole way? I slipped the bb in the hole and it went in about half way, but seems stuck pretty good. I can get it out but have to dig an pinch at it with needle nose piers (i.e. it is NOT easy to get back out). Any ideas what could happen since this ball plug obviously came out? Will I need a new carb eventually (as the ball is not included in a rebuild kit)?

Thanks again!
RC

I would carefully peen the end of the bore to retain the bb. When manufactured, a passage was bored up through the stem. Glad you brought it up as I wasn't sure where else it would come from! I would pull the starter and inspect the bolt holes for damage. Wobbled out holes are a bear. Hopefully no one installed a bolt that was too long that pushed the threads out or wrong thread. Sometimes the best you can do is clean the threads and JB 'em if they are damaged. Or maybe a metric bottoming tap and a next size up. I think I remember them being a 5/16 fine. Here's hoping the threads are as good as new! Glad to have helped.

Awesome site!!! Thank you to everybody that posted in this thread I wouldn't have been able to fix my snowblower without your help!!!

Hi,

I just discovered this forum after googling HMSK80. I've had my snow blower for about 15 years and it has served me well. It was professionally serviced 4 years ago and is now acting up again. By acting up I mean that it is stalling and/or surging. To keep it somewhat short here is where I stand: I bought some carb spray and sprayed out the carb. Also got a manual on line and adjusted the main jet, idle jet and throttle screw back to factory settings. Bought a rebuild kit and thus far replaced the o ring around the float and the main jet. Fired it up and it ran fine for approximately 10 minutes then died. Did this 2 more times. I would prime it and it would start right up. I was able to adjust (minimally) the jets and the throttle screw and surging was minimal. I noticed it would sometimes slow down a bit, but pick right back up again. My neighbor came over and we removed the carb and he is soaking it in cleaner and will finish with all the rebuild parts. I wonder it if is more than this. Why would it run fine for 10 minutes then die? Does the engine use a fuel filter that could be dirty. Gas is new and dosed with Seafoam. Any thoughts or help are appreciated.

Pete
Buffalo, NY

There is only a screen in the tank for a filter. Check your fuel cap and confirm it vents. Heck, whilst you have the carb off, run the line into a clean container for a spell. You will verify flow and double check for debris at the same time. Be sure the carb is in the upright position before installing the jet on the side.

I have an HM80 that runs but surges badly. When I took out the float bowl nut the two holes at the bottom looked fine but the tiny hole between the threaded areas appears not to go all the way through the side of the nut. Is it supposed to go all the way through straight across or does it take a turn? What can I use to free up the hole? I tried using a small needle but had no luck. This engine appears to be practically unused and probably dates back to the late 1970s.

The hole will just go into the center- not straight out the other side. A bread tie may help. Spray carb cleaner will help remove other varnish deposits. That and new fuel is a place to start.

Thanks tomplum, does anyone know what the size of that hole is supposed to be?

Okay I found out the hole is supposed to be .020" (.5 mm)

I have questions about the Welch plugs. What is behind these plugs and is something that can remover for hidden adjustments. My carb has two plugs one outside near the throttle and one inside near the main jet port. Does any one have any ideas why these are plugged. I have not remover them yet but was curious as to the purpose of these...thanks

There is a small mixing chamber behind the small one on the side. Sometimes removing this one will help get you where you need to go. Reseal the new plug for the side w/ nail polish after it has been peened in. Above the plug inside the bowl, inside there is a small metal tab on which is inscribed who really shot JFK.. Really just a chamber above the plug. No hidden adjustments.

Here is a link that might be useful: This may tell you more

Got a good laugh at that one. Thanks... I needed that.
I just couldn't see a carb with out any adjustments. My carb has had a slight high idle surge along with a bit of a back fire or miss on the exhaust side. I completely overhauled the carb / cleaned out all ports and reset the float level and still has that slight surge at high idle speed. No vacuum leaks any where and setting the idle speeds does not help any either. No miss fire on the ignition side since I have an in-line spark tester, it shows good continues spark. The gas tank was cleaned out and fuel line flushed out. New regular gas was put in and still have this miserable idle surge. This is why was asking about the Welch plugs. I will post on update after I pull the plug and fiddle with that a bit. Thanks again for your quick response.

The welch plugs are to block the holes they drill in the carb body;there's no other way they can connect the passages,without drilling holes ,and once the passages are connected,they have to seal them,so only the fuel metered by the jets will go to the passages............I never had to remove the welch plugs to clean the passages,but then again,I use compressed air with carb cleaner to clean,and so far it has never failed!

You may also want to try adding some Seafoam or you favorite fuel system cleaner to the tank. It isn't always successful with this however. Lots of jet spray through the passages down into the carb body while its running may help as well.

I had the same surging problem with my John Deere TRS 27. It has the HSMK80 engine. I bought a new carb, spark plug, fuel filter. I had it running great again thanks to the tips on this site.....cleaned my driveway twice last week....but now, I can't get it running again. I spray starting fluid in the carb and it runs great for about 3 seconds and dies again....won't restart. Has gas, fuel line is clear, primer works.... any ideas??? I am stumped.....

Good fuel isn't getting through the main jet. You might as well drop the bowl and look for water / debris, check flow and clean the main jet. If the tank and lines weren't cleaned, and fuel isn't new then make it so. If it won't run on the prime, just the starting fluid- that would indicate that the fuel itself is questionable.

Wow this 4 year old thread is full of good info.
I have a 8.5 HP Ariens ST8526LE 932105 Home depot special. This machine has always run rough with slight surging and popping. They are made to run good under load and idle like a Harley. There are no adjustments on the carburetor except idle and the governor. The manual 692509.pdf posted above is full of good information.
Common problems:
1.) Vapor lock in gas tank, cap is not venting and creates a vacuum in the tank like a straw with your finger on the top and gas cannot flow enough causing a staved condition that choking seems to help. Once you put it under load such as snow it will stall and you will start hitting the machine with your shovel. open cap slightly and air will rush in. Ice may be blocking vent. look in tank with a flashlight for debris or gremlins. leave gas open slightly to test.
2.) Clogged carb jets. Remove brass bowl nut and clean out small holes with tiny wire and carb cleaner. Sometimes the float stops floating and it will just flood the engine.
3.) Non-treated gas and it went stale. If it was left in over the summer, then pull the carb and get a new one or rebuild it with kit 632760B. Some people use stay-fresh, sta-bil or seafoam. Maybe running seafoam through will work, didn't work for me but they have a nice video.

Since the carbs are about $60 you may want to replace it and rebuild the old one.
The EPA carb 640052 has been replaced with 640349 which has no button drain in the bowl. If you want an adjustable carb the 632234A has been mentioned but now its Frankenstein
Look at the engine for the part number and series. LH318SA-15xxxx and find the parts diagrams. I found some info at outdoordistributors.com, perr.com, and ended up buying parts from psep.com because he had everything. I also got extra bowl gaskets, belts and a float since its small change and flat shipping.
Yeah the Home Depot special was missing the chute coupling, auger belt was loose and needed some adjustments out of the box but the EPA carb is what failed. Luckily I bought a shovel at the same time. Read the manual, it recommends good gas, stabilizer, RJ19LM plug gapped to .03 and 53-30 oil for 10W in your lawnmower.

Happy Snowblowing

"They are made to run good under load and idle like a Harley."

But does it "mark it's spot" like a Harley? heh heh

Very good info for those seeking help.

A quick clean up if I may:
RJ19LM plug gapped to .030 and 5W-30 oil.

What is your preferred method of storage? Do you run yours out of fuel , treat it -both?

Yes it will "mark its spot" if you push the primer bulb more than 3 times. Also when you lift the front end up a little gas might spill out of the air intake. The spill is OK and green, its got an EPA carb. I meant to write 5W-30 oil. In the North the 5W will provide a thin enough oil to get it started and then the 30 weight at operating temp. The 10W could be thick on those 10 degree days. I store my snowblower outside so it is always cold. I don't use synthetic oil because if you change oil every season it probably has marginal hours anyway.

For long term storage I've had better luck leaving stabilizer in with a half full tank. Sta-bil seems like the most popular brand around here. Its also good to start the machine a couple times along the year, maybe when the lawnmower makes its entrance and exit.

As for running it dry. I've heard the used gaskets don't like to be dry but I'm more concerned with the inevitable gas residue, treated or not. Some people pull the plug and put a squirt of fresh oil in the cylinder,pull the cord and then put in a new plug for storage. Tecumseh states its OK to leave treated gas while stored.

Its best to treat fuel right away and use the right amount of stabilizer. Sta-bil has a convenient measuring dispenser. Stabilizer also helps with drying water that may end up in the tank.

I've heard that fresh gas will go stale or separate after 1 month and the stabilizers claim to keep it for 1 year. I still go to the gas station after a few months. Dump the old gas my car and get new gas and mix it. Its good to have some gas around especially if you have a emergency generator.

The difference between the RJ19LM plug and J19LM is a resistor to reduce radio interference. Its functionally is the same but the J19LM may interfere with your laptop while your snowblowing causing you to drop it in from of the machine and right out the chute it goes. Now how will you google this helpful information.

To keep the linch pins from slipping out, allowing a wheel to roll ahead of me, I put aluminum tape over the pins and hubs. Duct tape would work but you don't get the chrome look.

Happy Snowblowing

Have a 5 year old 8hp MTD snow thrower with a HMSK80 tecumseh engine. The engine has just developed a gas leak. After refilling the tank with a small amount of gas it didn't start to leak until a pushed on the primer. The leak appears to be actually coming out of a hole when i push on the primer. The hole is above the bowl and on the left side, when viewed from the operators position and is inline with the small bracket that will take two screws for the outside cover/shield. Any help and suggestions will be appreciated

It could be that the float or float valve has issues or is too high. Does fuel continue to run out, or just a couple drips?

This 5-year old and 6 day thread was a lifesaver for me!!! I thought I should bump it up.

I have a 5 year old Toro with the 8 HP Tecumseh. This blower had the EPA carb on it and was surging over the past 2 years. Before snow hit I wanted to fix this and decided to follow the advice on this thread and update my carb to the 632334A with adjustments on it. I end up buying the carb off of eBay, cost $47 including shipping. It's an Oregon carb, it worked like a charm. Bolted right up to my snowblower, adjusted the carb and it's running better than ever. I wanted to thank everyone that added to this thread, great advice. If you are having trouble with your Tecumseh surging or simply running rough, I recommend reading this entire thread!

This is an excellent thread, and helped me a lot.
I had the same problem as mitch 2009. The carb leaked, but only when I primed it. It never leaked from the gravity feedline. I couldn't get it to start at a low speed setting. (didn't try high speed, I hate to wake it up from summer and right off make it run fast - I like to warm it up slow). I took the carb off, removed the bowl, and cleaned every orifice I could get into - no change. Finally I used the electric start and some starting fluid, and after a couple of seconds it sounded like it was going on its own, so I stopped squirting the fluid. It quickly started to run lame, and sounded like it was going to quit. This was at a low speed, so I revved it, and it started running strong again. However, it started surging.
There's a helpful thread on DoItYourself.com here:
http://forum.doityourself.com/outdoor-power-equipment-small-engines/120122-engine-surging-problem.html, and like was said in there, the carb and the governor were fighting each other. Also from there: "when you try to run the engine at idle and it cuts off, that indicates the idle circuit is restricted or even blocked." So I'm soaking it in cleaner now, in hopes of clearing that idle circuit (jet passage). My snowblower is a Sears model 536.886621 (MTD I think), and has the EPA carb, not the 632334A.

Here's a great parts list sight with a whole bunch of Tecumseh engine model parts lists, including the HMSK80 and HM80. Scroll down the list for specific engine. Once you get your engine, click on it and there is a list of all the specific suffixes (HMSK80-xxxxxxx)

http://www.landscapepower.com/tecumseh-partslist-pages/tecumseh_PDF_62.html

Also a refresh of the Tecumseh Service manual:

http://www.cpdonline.com/692509.pdf

Hope it helps all.

Where can I get a service/repair manual for HMSK 80

Ron , at the post just above your's is a adequate info site .

Can the ball plug fall out? If so, can't just simply be placed back where it came from? Seems like if it fell out its housing has been damaged. Will the engine still run without the ball plug?

Andrew

OK - I have a Tecumseh Carburetor 640169. It is on my Husqvarna snow thrower 927SBEXP. I have been messing with a surging problem for two years now. Mild in 2010 and so bad in 2011 that I can't stand it anymore. I have spent countless hours on the internet trying to solve the problem. In 2010 a can of carb cleaner solved it. Stored the machine empty of fuel as directed. All of my fuel has sea foam added. In 2010-11 season this this started bad and has surged bad. Starts great but NEVER stops surging. I rebuilt the carb and cleaned as best I could. The blower worked great for 3 uses. THEN - back where we started. After another rebuild of the carb and cleaning nothing worked. YES I cleaned ALL of the minute holes in the bowl nut MANY times. That is all I found on the web as to problems. After this last rebuild it was NO BETTER. I do NOT accept defeat so I got back on the web. While sitting here reading the same posts I remembered I didn't clean the IDLE RESTRICTOR SCREW (Tecumseh 640027
Idle Restrictor Screw). So I went and took the carb off for the 4,382nd time, removed the little $%$$%^$^ and cleaned the port from side to side AND directly from the end to the side to side port. (This port on the end was difficult to get "connected" to the side to side port but after some influence with a TINY wire it worked. Replaced carb and it runs LIKE A CHAMP!!!! Sorry for the long thread but I have not seen anyone post this as a solution. I hope this helps someone else in my frustrated situation. This screw can be removed without removing the carb and will be the first thing I clean next time before a complete rebuild. Part # 20 found at this link
http://www.partstree.com/parts/?lc=tecumseh&mn=TEC-640026&dn=CASERIES_AE81640026-CA

Hello fellow surgers.
I have a 1996 Craftsman 30" rear engine rider with a Tecumseh 13HP OHV engine. I had let this mower sit for 4-5 years, and went to fire it up. NO GO. So I just did a quick clean out of the bad gas deposits, and the mower fired up and ran, however it surged a couple hundred RPM throughout the entire throttle range and idle. So I cleaned it out again. Just with a can of carb/throttle body cleaner, thought I did a good job, it looked clean to my eye, but that was NOT good enough for it. But it still surged. I said the heck with it and used it for a year or so.
I decided to tackle the surge problem again. With no short cuts. Now I was going to tackle it like the multiple hundreds of Toyota carbs I have rebuilt over the last 30+ years as a master tech, and not like a back yard quickie.

Troubleshooting:
Surging: throughout throttle range.
Carb restriction.
R+R (remove & replace) and D+A (disassemble & assemble) carburetor assembly.
Pull out welch plugs and separate each & every piece from each other.
I used:
- 1) Factory Tecumseh-Power kit # 632760B
- 1) 1 gal. Carb dip can with strainer from parts store.
- 1) spray can throttle body cleaner.
- compressed air (air in a can for cleaning computers can be used to check passages for flow along with the pressurized cleaners, if you do not have a compressor.
- misc) small wires
- basic hand tools ( screw drivers, wrenches etc. I used the end of a short socket extension to reinstall the welch plugs and sealing the external side welch plug with touch up paint.)

It is best to soak the carburetor pieces in a dip tank for 24 - 48 hours to dissolve and soften ALL of the deposits. Agitated (plunge up & down in tank fluid) every few hours to flush fluid throughout pieces in dip tank
Then I use compressed air and torch tip cleaners and or small gauge wires to clear out all passages in each affected piece. Re-cleaned with spray cleaner and thorough blow out everything again.
CLEAN, CLEAN, CLEAN!
It is critical to make sure the main fuel jet is cleared of all obstructions.
NOTE: There is a very, very tiny orifice port in the fuel bowl retaining nut ( a hollowed out bolt with precise fuel ports that secures the bowl to the carb body ) between the 2 threaded areas, is a port called the "idle fuel transfer passage", this is a SURGING problem throughout the entire throttle range, from idle to WOT if this is plugged or minutely restricted. It also has 1 or 2 main fuel ports, depending on model, at the head end that must be CLEAN along with the center passageway.

It is important not to accept a "half done" clean out and expect things to run perfect. That is what I did and I got SURGED!
After I did a proper clean and rebuild of the carb, the mower runs like it did when it was new.
I ran engine until warmed up to normal ops temp. and adjusted the idle mixture (only mix adjustment on my carb).
I now have a nice smooth idle and smooth acceleration and WOT (wide open throttle) response. It is now PERRRfect!

This video helped me solve my surging problem. Nobody has ever identified this little screw. I saw the cap on the side of the carburetor but never realized there was a screw behind it until I saw the video.
The axial hole on the end of the screw is deceiving in that it is not the hole being referred too. The actual hole is at the bottom of this pilot hole and is about the size of a wire on the paint scraping brush he refers to. I had comletely disassembled the carb and cleaned everthing and it still surged. This screw was the problem.

Here is a link that might be useful: tecumseh carburetor surging fix