Tecumseh Problem

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  #1  
Old 08-09-08, 02:43 PM
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Tecumseh Problem

I'm getting back to working on my own equipment and last winter I had a problem with my HM80 surging with no load on it. The Carb was soaked and rebuilt with an OEM Tecumseh kit and I still have the problem with it surging. The bowl nut holes are clean and the bowl adjustment screw (high speed adj.) is clean and polished. If I richen the high speed screw until the surge goes away it doesnt run cleanly - it seems to run slightly rich still. Going leaner brings the surge back. I've raised/lowered the float height with the same result. The engine runs fine at idles and decellerates fine. When Accelerating engine to full throttle it blows a small amount of black smoke and seems to be mostly there but wont run completely smooth. I verified the seat is still in there and the needle seats to it nicely but I just don't know what else to do. Replaced the spark plug with a brand new one and gapped to .030". The little bit of fuel that was in the tank since I last used it had Sta-Bil in it and I added about 1/2 tank fresh fuel w/o any additives in it. What am I missing?

Model: HM80 155283K Serial: 5203D
 

Last edited by Legal v8; 08-09-08 at 02:44 PM. Reason: added model/serial numbers.
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  #2  
Old 08-09-08, 06:48 PM
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Did you use kit 632347? , remove side welch plug before soaking? Can you hear metering pin if you shake carb? Did you replace both carb gaskets? Carb gasket PN# 33263 and Intake PN# 27915A? Did you let engine warm up before adjusting high speed needle and the adjust idle mixture screw?
 
  #3  
Old 08-10-08, 05:49 AM
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Yes sir. I used that kit and replaced the proper gaskets - and yes the engine was warm. The float and needle operate properly and everything is sealing. The welch plugs were removed before soaking and new ones (from kit) were replaced as well. No leaks. Right now the float is set about 1/16" lower than "level" with bottom of carb body (with carb installed).
 
  #4  
Old 08-10-08, 10:13 AM
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This is the same engine you posted about in Dec. 07 and same problem. If you can't hear/feel the metering pin rattle the only option is a new carburetor.

Look at the suggestions from back then.
http://forum.doityourself.com/showthread.php?t=329106
 
  #5  
Old 08-10-08, 01:50 PM
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With the carb off and giving it a shake I do hear stuff moving around in the carb. I'll drop the carb off the engine and pull it all apart again. You say this metering pin is in the idle screw passage yet it will cause a surge at full throttle? That doesnt make much sense but I'll look into it.
 
  #6  
Old 08-10-08, 06:49 PM
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The carburetor uses fuel drawn through the idle circuit at higher throttle positions. If the idle circuit is blocked the throttle plate cycles full open and back to close compensating for too much or too little fuel. The throttle plate movement is what causes the surging.

On the other hand, if you think it is not the carburetor then it could be the governor. Get the engine manual and adjust the governor according to Chapter 4.

Only these two things could possibly cause the surging.

My money is on the carburetor.

Good luck
 
  #7  
Old 08-11-08, 04:22 AM
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I'd bet its the carb too. It is an old engine. I didn't have time to tear it apart yesterday but I'll take it apart today and see what happens.
 
  #8  
Old 08-11-08, 06:53 PM
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Tecumseh

I have never been able to keep a Tecumseh running. Mine used to surge like yours, I could never keep the governor set; it would always be running too fast or slow. I had to keep changing the fuel from the bowl, even though it was kept in a dry shed. I have owned probably ten Briggs engines over the years and never had these problems with any of them. I fought with this thing for over five years before I finally got a Briggs to put on the mower and chucked the old Tecumseh in a dumpster.
 
  #9  
Old 08-12-08, 04:18 AM
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I am a Die-Hard Briggs fan myself.. and I would put a Briggs on this Snowblower in a heartbeat but for one I dont have any briggs' engines left and even if I did I've never seen a Briggs with two crankshafts. (This is a Snowblower Engine w/ two cranks - one's for reverse and the other is the main shaft running the auger and forward gears)

I have 3 9hp Hondas but they only have the one crankshaft.

Aside from this problem this engine ran PERFECT before the soak.. The only thing was the primer would squirt gas out the front of the carb instead of into the engine. I figured soaking it would clear out that primer passage. I'm going to get some of that Carb Cleaner Airman mentioned in the other thread and see if I can get that metering pin loose otherwise I'll get another carb.
 
  #10  
Old 08-12-08, 04:28 AM
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That second "crankshaft" you refer to is the camshaft.
Mike
 
  #11  
Old 08-12-08, 01:20 PM
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I guess since I haven't had a Tec. Snow engine apart I didn't know they used the camshaft to drive accessories (ie: reverse).. I guess you learn something new everyday..
 
  #12  
Old 08-12-08, 03:34 PM
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Guy's I am new to this forum stuff, and maybe I am wrong. But, It is an older engine with some hours on it, a little ring wear and throttle shaft wear.... If it runs good under load and the surge off load is not real bad - would it be ok to leave it surge?

I have a craftsman tractor with a kohler - under a load ran great wouldn't even skip a beat in heavy grass, but it surged like crazy with no load right from new - I should have leaft it a lone - adjusted governor with out the serves manual.
Now I own it and have to pull the cv15.5s down to put the governor back together........ stop laughing it's not funny!!!


Ok, maybe a little.
 
  #13  
Old 12-07-08, 09:56 PM
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Would I be safe to assume I now have to adjust the governor? Does anyone have a few pages out of a service manual that could scan the pages dealing with governor adjustment?
 

Last edited by 30yearTech; 12-08-08 at 04:47 PM.
  #14  
Old 12-08-08, 05:22 AM
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Legal, does this engine have points? You said it is about 25 years old which is about the time they started to switch to electronic ignitions. If it does have points, might need new ones (which is a PITA). Also, does it have a primer? a broken primer line could cause your problem. Tecumseh primers push air , not gas, into the carb essentianlly "flooding" the carb. If the primer line (or primer bulb)is cracked or broken, the carb is sucking air thru it.
 
  #15  
Old 12-08-08, 01:45 PM
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I don't know if it has points or not. I believe the engine and blower unit are from 1985. I'm gonna look into whether or not it has points. It does have a primer. the bulb is in good shape and I already replaced the hose between the bulb and the carburetor.

The serial number/model numbers (155283K 5203D) show it was made July 22nd 1985. I haven't been able to find out online if it has points or not yet.
 
  #16  
Old 12-08-08, 02:09 PM
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just looked it up on my microfiche. no points
 
  #17  
Old 12-08-08, 04:50 PM
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Originally Posted by Legal v8 View Post
Would I be safe to assume I now have to adjust the governor? Does anyone have a few pages out of a service manual that could scan the pages dealing with governor adjustment?

I am sorry, but I accidentally edited your post. I clicked on the edit button instead of the quote button by mistake. I did not realize that's what I did until I had already deleted some of your post. I only wanted to reference the above info as it's possible that all you need is a governor adjustment, and I wanted to give you a link for a service manual for your engine.

Once again... Sorry....

http://www.cpdonline.com/692509.pdf
 
  #18  
Old 12-09-08, 06:27 PM
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Originally Posted by 30yearTech View Post
I am sorry, but I accidentally edited your post. I clicked on the edit button instead of the quote button by mistake. I did not realize that's what I did until I had already deleted some of your post. I only wanted to reference the above info as it's possible that all you need is a governor adjustment, and I wanted to give you a link for a service manual for your engine.

Once again... Sorry....

http://www.cpdonline.com/692509.pdf
No problem.. I can probably put the information back there since I still have browser history if I feel like it later.. Thanks for the info. I'll print the stuff off and try to get it buttoned back up.. Thanks!
 
  #19  
Old 12-09-08, 11:02 PM
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I don't know about the engines on snowblowers, but I do know that on some tecumseh carbs, the air filter housing screws at the end of the carb must be in place or the carb will run lean if at all. You'rs may not be that way, but if you don't have those holes blocked, try it and see if it improves. Apparently those holes share space with one of the passages in the carb.
 
  #20  
Old 12-14-08, 06:39 AM
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Originally Posted by cheese View Post
I don't know about the engines on snowblowers, but I do know that on some tecumseh carbs, the air filter housing screws at the end of the carb must be in place or the carb will run lean if at all. You'rs may not be that way, but if you don't have those holes blocked, try it and see if it improves. Apparently those holes share space with one of the passages in the carb.
On the Snowblowers they don't have air filters. They just have a little mechanism for the choke that screws into the end of the carb. At this point those screws are in and tight, and the mounting screws on the intake manifold are tight as well. I am going to print the stuff regarding adjusting the governor. I am pretty sure that this is the problem. It's got good spark and compression is pretty good still and with a new carb the only thing left is the Gov. If adjustment doesnt cure the problem then maybe tearing the case apart and see if its damaged inside.. I'm gonna adjust the Gov. today and see what happens and then go from there..
 
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