# Tecumseh 8HP Motor Surging - Carb Issue?



## ts8169 (Nov 9, 2015)

Hey all,

I have been having a ton of carburetor issues. I could not get the Tecumseh motor in my Toro to run clean, not stall, not run without choke...whatever. I finally took a chance and bought 1 of the $15 Carburetors off eBay. Before installing it I swapped out (2) O-rings, the bowl gasket and bowl jet gasket with OEM Tecumseh replacements. I reinstalled the new carb and filled with fresh treated gas. The snowblower started right up and seemed ok with each turn of the choke. With the choke off, the motor started to surge and pop and wouldn't stop. The bowl jet was turned out 1.5. No adjustments here did any good. The screw on the side (Idle mixture?) was 1 turn out. Adjustments here didn't seem to do much. I did notice gas coming out from the choke plate prior to starting. Gap on the float looked to be within Tecumseh specs though. Any thoughts?


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## e.fisher26 (Nov 6, 2016)

Bowl needle was at 1.5, did u adjust it while running full throttle?


-efisher-


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## ts8169 (Nov 9, 2015)

Yes, the bowl jet/needle was 1.5 turns out. I adjusted from 1.0 to 2.0 turns out with no noticeable difference in the motor. All at full throttle.

The motor did start up for the first time in 9 months - first pull. Can't be too bad.


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## e.fisher26 (Nov 6, 2016)

When I installed new eBay carb I put the governor linkage in wrong hole. It ran but surged. Also, loosen the low adjustment screw and see if it runs different (side screw not bowl )



-efisher-


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## Mike C. (Jan 28, 2016)

I chased a problem like this not too long ago on a Tecumseh HM80 snowblower engine.I was convinced it was a carb issue.Come to find out,the engine was old enough to have points/condenser and they were both shot.

Another time I found out that the new sparkplug I installed was just as bad as the old plug.

Ever checked the valve clearances on your engine?


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## ts8169 (Nov 9, 2015)

My engine is also an HM80. Based on the serial number on the blower, it's a 1990 so 25 years until my problems started. I don't have enough skills to check the valve clearance but have watched video's on youtube to see how it's done. I definitely do not have the special tools. What are points/condensers?

My problems all started after I left gas in the tank all summer, then started it in the fall. Was kicking myself. After that when I pulled the carb bowl and saw the mixture of super rich fuel & water, tah dah... So I always assumed it was that carb. I've changed the spark plug, fuel line, cleaned gas tank with carb cleaner, changed multiple parts to the old carb, and now the new carb. Muffler is toast but I can't see that causing issues other than noise.

Before I pulled the old carb, I marked the hole for the governor, then soaked the carb. Guess where my mark went.... I'm about 99.9% sure it's correct though.


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## e.fisher26 (Nov 6, 2016)

Points/condenser is like the coil, builds up power for spark from magnets on the inside of flywheel, unfortunately the flywheel needs removal to do this. Take off starter cvr, take off flywheel nut, take a prybar and apply pressure to back of flywheel, and tap end of crank shaft with hammer. 


-efisher-


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## Grunt (Nov 11, 2013)

ts8169 said:


> My engine is also an HM80. Based on the serial number on the blower, it's a 1990 .


I believe points ignition stopped in the early 1980's, so your motor is solid state with no points to worry about. 

If your carb is spitting gas from the carb throat, there is a good chance your intake valve is not seating completely. Checking the valve clearance as recommended earlier is a good place to start trouble shooting the poor performance.


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## e.fisher26 (Nov 6, 2016)

Might have to check that, my dad bought a new tecumseh in roughly 92, and it had points. I know this because I used this same eng on a snoblower just few years ago now, had no spark, I got it own to points, change it all out, got it back together, still nothing, turned out it was arching out on the ground wire. That was my first points job, didn't know to check that first! Lol


-efisher-


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## Grunt (Nov 11, 2013)

Easiest way to tell if it has points. Check the parts list for the engine in question, or pull off the recoil shroud and see if the coil is mounted above the flywheel. If it is, the ignition is solid state.


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## driz (Dec 19, 2013)

Well you learned your real lesson with this one. Never ever leave a small carbed engine sitting with fuel in the tank during layup! Dump the tank and then run it dry. With today's gas no amount of stabilizer will guarantee it won't go bad or just grow its own water wnd corrode the small needles and seats. Even though made of brass they can still grow crud which causes what you had. Pay the extra for ethanol free as well and save yourself all this sort of thing.


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## ts8169 (Nov 9, 2015)

Yah, no kidding driz. You said it.

I checked the parts diagram for my HM80 Tecumseh:
_Tecumseh 35135
Solid State ASM_
Looks like the part is only about $15. Easy to replace a solid-state coil?

I also found an OEM Tecumseh Carb online for $78.23. I'm assuming this is a better carb than whatever I bought off ebay and not sure if it's worth my money. The eBay carbs do seem to get good reviews (online, on this forum & even DonyBoy on youtube). I know some people have had to make minor adjustments to them which is why I swapped out the seals/gaskets..


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## Jackmels (Feb 18, 2013)

If it runs at all, you don't need a new coil if it's a solid state coil. Make sure the carb gaskets are sealed well, and drop the bowl to see if there is any crap in there from decomposing fuel lines. Don't be afraid to adjust the carb (both screws) while the engine is running.


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## Mike C. (Jan 28, 2016)

Grunt said:


> Easiest way to tell if it has points. Check the parts list for the engine in question, or pull off the recoil shroud and see if the coil is mounted above the flywheel. If it is, the ignition is solid state.


I should have known that my early 80's HM80 had points merely by the fact that I had previously observed that the ignition wire was offset to one side on the starter shroud.If it was solid state,the ignition wire would be in the center of the edge of the shroud(inline with the plug).


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## Bluejoe (Nov 29, 2016)

When you clean/rebuild carburetors you have look at what carb you have. Is there any other things you should look for like cleaning out obstructed holes. The tiny ones which go behind the Welch plugs or how about the ball check valves. Don't bind them up. And then there is how everything goes back together. Then last but not least correct low & high idle tuning. One or more of these could cause the problem.


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## ts8169 (Nov 9, 2015)

Bluejoe: The carb is brand new. That's why I'm stumped and posted to site. I'm going to move on to the gas tank and soak the shut-off valve in cleaner. Maybe carb isn't getting steady flow of fuel.


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## classiccat (Mar 1, 2014)

ts8169 said:


> Yes, the bowl jet/needle was 1.5 turns out. I adjusted from 1.0 to 2.0 turns out with no noticeable difference in the motor. All at full throttle.
> 
> The motor did start up for the first time in 9 months - first pull. Can't be too bad.


At no load, the idle jet (adjustment &/or obstruction) is often the culprit; the throttle butterfly should be barely open.

does the surging lessen when you engage the auger & traction?


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## ts8169 (Nov 9, 2015)

classiccat said:


> At no load, the idle jet (adjustment &/or obstruction) is often the culprit; the throttle butterfly should be barely open.
> 
> does the surging lessen when you engage the auger & traction?


I did try engaging the auger & traction and it didn't seem to do much good. The butterfly is mostly closed but with the surging, the governor is opening it somewhat. I'm also getting popping / backfiring every 10 seconds or so. It did run better with 1 turn choked, but the final turn of the choke to fully off, 10 seconds later, surging/popping starts.

We're supposed to get some measurable snow in the next couple days so it will be until at least then before I can try putting any real load on. Wondering if it's worth the $80 for a new OEM Tecumseh Carb. Not sure I trust this $15 eBay model.....

Thanks for all the responses


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## dodgetrucker (Jan 15, 2016)

I'd go OEM any day of the week even though it costs more, you get what you pay for. bot besides that the mixture screw in the side has to be adjusted while at idle, it won't do a thing for how it runs at full throttle
and Grunt; you're not far away, right up rt 45 from me about 1/2 hour.....


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## Grunt (Nov 11, 2013)

dodgetrucker said:


> Grunt; you're not far away, right up rt 45 from me about 1/2 hour.....


 I was just at RUSSO's picking up some parts and driveway salt.


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## 43128 (Feb 14, 2014)

the aftermarket carbs are very good quality in my experience and usually work out of the box. i chased an issue like this on my hm80 that was on my toro 824, it turned out the exhaust valve stem was stretched out. if i were you i would check the valves


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## dodgetrucker (Jan 15, 2016)

Yeah, I need to hit them up for a few things too. haven't been in there yet. I was in their location up north once, near Rosemont and OHare because I was "in the area" for something else.


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## Ian Ariens 924 (Dec 22, 2015)

Might be worth the time to readjust the governor.
The older Tecumseh engines have an adjustment in the linkage,a small flat screw,you can get at it just behind the choke entrance.Its the high speed adjustment,if you have one
Or readjust it at the governor arm.
I'd try that


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## thool (Jul 25, 2016)

e.fisher26 said:


> Points/condenser is like the coil, builds up power for spark from magnets on the inside of flywheel, unfortunately the flywheel needs removal to do this. Take off starter cvr, take off flywheel nut, take a prybar and apply pressure to back of flywheel, and tap end of crank shaft with hammer.
> 
> 
> -efisher-


Just make sure you screw shaft the nut on a couple threads before trying to remove the flywheel. When the flywheel comes off, that nut will prevent it from flying off and crashing to the floor.

Come to think of it, maybe that is why they call it a fly wheel? :icon_smile_shock:


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## kNewc (Nov 22, 2016)

I think it needs a good carb clean. Very common with motors and surging.


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## Jackmels (Feb 18, 2013)

+1 43128 on the valves. Easy to Adjust them, Pull Carb and Valve Breather Assy. Lift Valve With Screwdriver. Then Insert a File between Valve Stem and lifter, and File Valve stem until You Get Clearance. Valve Spring keeps Pressure while you File. Just did this Today to an 8hp Toro.


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## ts8169 (Nov 9, 2015)

Jackmels said:


> +1 43128 on the valves. Easy to Adjust them, Pull Carb and Valve Breather Assy. Lift Valve With Screwdriver. Then Insert a File between Valve Stem and lifter, and File Valve stem until You Get Clearance. Valve Spring keeps Pressure while you File. Just did this Today to an 8hp Toro.


I thought you had to pull the head and use grinding paste to do this? Either way, it seems a little beyond my abilities. What would a shop charge to clean/ adjust the valves? +/-....


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## ts8169 (Nov 9, 2015)

Just an update: We had measurable snow over the weekend so I ran the blower under load. To recap... it's a brand new eBay carb 632334A for Tecumseh HM80 with swapped gaskets & o-rings at the bowl, bowl jet, idle mixture... with OEM gaskets. (DonyBoy recommended this..). It starts right up on first pull. At full throttle & no choke, it's surging and popping. Under load it was able to blow light snow in first gear, but much beyond that it was ready to stall. Low throttle & no load = Guaranteed stall. Adjustments to main jet and idle mixture made no difference in performance.

I shut it down, back to the garage, took off the main jet, installed the OEM main jet off the OEM carb (cleaned) and restarted. Again surging at full throttle. Started blowing snow and my Toro 824 was suddenly having fun. With no load it's still surging, but at least I'm back in business blowing snow. My back can't handle shoveling anymore... Many have had good results with these eBay/Amazon carbs but maybe I got a bad one. I do agree with others on the valves. Unfortunately I'm not that savvy with small engines.


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## Vermont007 (Mar 29, 2015)

I wonder if the OP's Tecumseh Engine has a carburetor similar to 640349, which is on many Snowblowers and has a hidden *Idle Restrictor Screw* on the side.

When allowed to collect fuel deposits in blocked passages of this screw, it causes chronic surging conditions, especially when NOT under load . . . . which sounds very similar to the problems with the OP.

Here's a video showing the correction of this surging . . . . just in case it's the same kind of Tecumseh Carburetor:


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## cranman (Jan 23, 2016)

I just did a H70 carb over the was surging from a Jacobsen that I am ressurecting....I took pieces from three carbs to make one and it surged to beat ****.....needle nose pliers and bent the rod to the carb from the governer slightly....cured!


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## ts8169 (Nov 9, 2015)

Thanks Vermont007. I did see this video and my carb is adjustable. So the idle mixture screw is more like a needle with spring, washer and O-ring. I swapped the o-ring with OEM but maybe I should swap the whole piece with OEM. Or just buy a whole new OEM carb. Or just drain gas out of the machine every spring like I should have done to begin with.

One of these days I'll get up your way Vermont007. I hear the Mt.Biking and "The Jay-Cloud" are fantastic!


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