# Tecumseh ah520 surging problem



## woodygjw (Dec 10, 2008)

Hi, I have a MTD snow blower with a tecumseh ah520 engine that surges when it is at rest without the auger engaged. I think that the governor needs to be adjusted and I have the manual for the engine, but it does not list the recommended rpm for this engine. It does not have a throttle adjustment, it just runs at one speed. Does anyone know what the speed should be? I have rebuilt the carb, and the engine runs perfect with the auger engaged and under a load. I have one of those vibra-tach things to check it, I am just not sure where I should set it at. Any help would be great. Thanks.

Greg


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## bgbass (Jan 11, 2008)

A lot of the smowblowers will surge when not under load if its running ok under load leave it


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## justin3 (Apr 10, 2007)

bgbass said:


> A lot of the smowblowers will surge when not under load if its running ok under load leave it


 Your engine is too old to have an EPA restricted carburator, so your motor should NOT surge at idle. There should be a mixture screw on the side of your carburetor, turn it counter-clockwise 1/8 of a turn and see if your situation improves. If not you have a restriction in your low idle circuit of your carburetor. Cleaning out the carb and maybe even getting a rebuild kit should solve your problem.


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## paulr44 (Oct 14, 2008)

If it only surges a little, and works fine under load, then as bgbass said leave it alone.

If it surges wildly, then there's probably a fuel restriction as Justin said. Adjusting the high-speed mixture screw as Justin indicates (the screw furthest from the engine on the side of the carb.) should clear it up.

That's a 2-stroke engine, and will run somewhat rough and surge somewhat free-load, but then if you've had it since new you know that.

3400 to 3600 RPM is about the max. those normally run, but if you post the engine spec. number we could look it up. It could end up that it is supposed to run at 3200, or even 4000.


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## woodygjw (Dec 10, 2008)

Thanks for all the suggestions. I was getting worse as it would almost die while surging. I did tear apart the carb again and found a passage blocked. I am hoping to get it all back together sometime this week and will post results.


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## woodygjw (Dec 10, 2008)

OK, got it back together and still have problems. It will run good for a few seconds and then act like you turn off the ignition, and then it will come back to life. I have replaced the points, condenser and coil earlier. Carb has been rebuilt. I think I did something stupid and put in the wrong plug. I have a RCJ8Y champion in there right now, but I think I need a RJ18YC. My snowblower manual does not list the correct plug and the original plug is long gone. Can anyone confirm this is the correct plug? The numbers on the engine tag are 1589A and 9239. When it does not do this surging thing, it will move snow very well. I would also like to set the RPM on it but the manual says to refer to the microfiche card that I do not have access to. Thanks for any help it is greatly appreciated.


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## hankster (Jan 1, 1998)

You still have a carb problem. Maybe you put it back together incorrectly. That plug is correct.


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## bgbass (Jan 11, 2008)

Try this when its running take a can of carb. cleaner and spray around the mating surfaces and the throttle rod see it it smoothes out. have run into a lot of the throttle rods suking air by.


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## hankster (Jan 1, 1998)

Good thought, forgot about that. Also spray around the governor shaft that sticks thru the side of the block... they can wear too. But in most cases you'll see fuel/oil seapage in that area.


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## paulr44 (Oct 14, 2008)

hankster said:


> Good thought, forgot about that. Also spray around the governor shaft that sticks thru the side of the block... they can wear too. But in most cases you'll see fuel/oil seapage in that area.


Hank, momentary senior moment...Tecumseh 2-strokes have air-vane governors. It'll pass, mine do... : )


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## 30yearTech (Sep 14, 2006)

paulr44 said:


> Hank, momentary senior moment...Tecumseh 2-strokes have air-vane governors. It'll pass, mine do... : )


Some of the 2-strokes do have internal governors, but none of the AH series do.


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## hankster (Jan 1, 1998)

Oppps. didn't catch the AH part. Most I work on have the internal gov.


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## justin3 (Apr 10, 2007)

Could also be a bad bottom end seal or crankshaft seal leaking slightly.


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## woodygjw (Dec 10, 2008)

Alright, thanks for the tips. I will try them out sometime this weekend.


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## pyro_maniac69 (Aug 12, 2007)

hankster said:


> Oppps. didn't catch the AH part. Most I work on have the internal gov.


ya he has about a 3 horse motor

the 4.5 and up have internal....and I believe those are HSK engines


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## woodygjw (Dec 10, 2008)

No luck so far. I sprayed carburetor cleaner around the carb while running and not any difference. I can't get to all sealing surfaces on the engine the way it is mounted in the snow blower to spray those. I have another carburetor on the way and I will be changing all gaskets and seals on the engine to make sure it is air tight. I will post my findings when I get all the parts installed, probably sometime towards the end of the week. Thanks for all the help so far.:thumbsup:


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## woodygjw (Dec 10, 2008)

OK, I finally had more time to look at this and the crackshaft seals did look like they were leaking. Now here is my problem, I think I need the 510105 seal, which is not to be found anywhere. I did find a couple places that said to use the 510319 seal. I received it and it is not going to fit. The old setup used a seal with a retaining ring on top followed by a snap ring. The new seal looks like a press in type, and it is too wide to fit the bore.

Does anyone know of a seal that will fit my engine and where to get it? Again, my numbers on the tag are 1589A and 9239. Any help would be greatly appreciated, thanks.


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## paulr44 (Oct 14, 2008)

If it really calls for a 510105, that part was made NLA 3 years ago. I can look the engine up on older fiche, but it's no longer on any IPL system online that I can find.
Paul


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## woodygjw (Dec 10, 2008)

Thanks Paul. I was looking on ebay yesterday and found a good used engine for 35.00. I may revisit this engine later on but right now I want to get this snowblower working for my dad; I am tired of hauling mine over to his house


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## BODNA2 (Apr 21, 2009)

I Have A Older Areins Snow Blower With A Tecumseh Engine And The Srew That Holds The Lgoverno Lever Rod To The Governor Shaft Came Out And So Did The Rod From The Vane Meter In Which Hole Sould The Rod Be In (ther Are Three Holes) And Which Way Do You Adjust The Governor Shaft And Lever Has I Am Having Alot Of Trouble For It To Run


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