Wondering why there is a miss with a Tecumseh LEV120 - Snowblower Forum : Snow Blower Forums
 
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post #1 of 7 Old 04-06-2016, 09:07 AM Thread Starter
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Wondering why there is a miss with a Tecumseh LEV120

I ended up buying a used Ariens ST622 walk-behind string trimmer. It has a 6hp Tecumseh LEV120 engine on it.

Well, I get it, prime it, it starts on the first pull. Great. Well, without the bale pulled back and the engine under load with the trimmer head, it has something of a "miss" to it. With the bale pulled back and the engine under load there is no miss/sputter to it at all. It runs consistent and powerful.

So, the question I have is, is there a problem with the carb or coil and should I pull the carb apart and clean/rebuild it? Should I replace the coil?

I put a brand new NGK plug in it gapped properly and it made no difference the way it runs. There is no smoke out of the engine and the oil is new (SAE 30 per specs).

I just thought the no-load sputter was a thing of the 2-cycle Tecumseh engines and the 4-cycles ran solid, or is that none of the emissions non-adjustable Tecumseh carbs all have the sputter issue without load?

I have no issue tearing into the carb. It isn't a big deal at all, just that I don't want it to waste the time and effort if it isn't going to change anything. A new carb is only $27 and a new coil is $15... Again, not a big deal, but I don't want to just throw money away if there is no problem.

Most of the videos I can find of LEV120 engines running are those on lawn mowers, and all of them are running at full throttle and under load from the blade from the start. If I start the ST622 and have the bale pulled from the start I don't get a sputtering/miss at all either.

But, I did find a couple videos of this engine being used on the same kind of walk-behind trimmers and a few of them also had the same miss/sputter without the head spinning, but there was also commentary about the miss/sputter as well on them, in that they figured there was a problem.

Any input is appreciated.

Last edited by DennisP; 04-06-2016 at 09:11 AM.
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post #2 of 7 Old 04-06-2016, 09:24 AM
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If those have a spark arrestor in the muffler check taht the screen is not plugged up.....




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post #3 of 7 Old 04-06-2016, 02:16 PM Thread Starter
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Nope, no spark arrestor in the muffler.

I ended up pulling and redoing the carb... In the process the float wouldn't sit properly, so I bent the tab the way you are supposed to... In the process I think I ended up ripping the float, since after I got things back together it ran for a while then flooded out.

So I have a few floats from older carbs on hand (amazing how quickly you acquire parts), so I ended up ordering up a new needle and gasket kit and once I get that in I will redo the float.

But, while it was running fine, it was still popping a bit while running without the load.

I think I will also go the extra mile and pull the whole carb and intake again and pull the valve-cover and check to make sure there is proper valve clearence. Would suck to have a stretched exhaust valve or something.

Update: Well, I did the above, plenty of clearence on the exhaust valve (like at least .006") and the intake valve has about .004" or so. I also stole all the parts from one of the new aftermarket carbs I had.

Starts on the first pull, but still has the stumble/miss/stutter without load.

I went ahead and ordered a new coil for it. If that doesn't change it I am just going to say screw it and run it the way it is. I am not inclined to pull the top of the head off.

I will say that whatever crap gas they had running in it before was foul. I drained it and put the good stuff in it. Maybe it just needs to have a few tanks of good gas and seafoam to help it out as well. I know I burned through at least 1/3 tank of gas while testing it. It is definitely not a fuel efficient engine, as it took only about 15 minutes to burn through that much. More than sufficient for my needs, but I can see if you had a lot of land to do it would go through gas quite a bit. Maybe with a full tank you will get between 50 minutes and an hour of use?
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post #4 of 7 Old 04-06-2016, 05:46 PM
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If it's a non adjustable carb, pick the little black plastic cap off the side (just to the left of the primer. There will be a brass jet in there. Pull that and clean the tiny little end hole with a bread tie wire. It should clear the stumble up. If you already did, disregard.
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post #5 of 7 Old 04-06-2016, 10:59 PM
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Quote:
Originally Posted by jtclays View Post
If it's a non adjustable carb, pick the little black plastic cap off the side (just to the left of the primer. There will be a brass jet in there. Pull that and clean the tiny little end hole with a bread tie wire. It should clear the stumble up. If you already did, disregard.

sometimes all bore those out a bit it with a torch tip cleaner or micro drill. a lot of late model tecumsehs run extremely lean from the factory and this helps with surging and starting issues
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post #6 of 7 Old 04-07-2016, 05:45 AM Thread Starter
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Yeah, everything is clean.

Can the idle jet (the one with the black cap) cause a lean stumble at full throttle with no load?

If so, I have no issue drilling that out... Just have to find a drill small enough.

There is no surging and it starts right up...

I did swap in another coil I had from a HSK850 (same coil), and it didn't change anything. I still have a brand new coil coming in (the original coil had a damaged potting near the cutoff tab, don't know if I did that removing it, or if it was like that for a while, but it will get a new coil regardless).

One thing I did do is change the oil. The guy I bought it from runs a small engine shop and said he changed the oil and cleaned the carb, but I could tell the carb was never removed, the bowl nut may have been, but the bowl was never off, and when I checked the oil it was really low. So I put some SAE 30 I had on the shelf in for the screwing around I was doing. Well, when I finally looked at the manual, they want you to dump the oil out the dipstick tube to change it.

So, I run it warm, plop it over on it's side and pull the dipstick. Out came a ton of grey and silver. Normally I would be very concerned, but, if this thing had it's oil changed at a small engine shop, they probably just siphoned it out the tube, never putting it on it's side. And I am sure they never warmed it up first before they did it. So I got to be the lucky one to get drain out all the gunk at the bottom of the sump.

I ended up putting in synthetic 5w30 Mobile 1 High Mileage (better additive package to it). Spec calls for 21oz, but I just did it to the full line on the dipstick. Basically it fills the sump to the top of the dipstick tube hole. And from what I am finding out, that seems to be the factory fill point on a lot of smaller engines (a few chondas I have are like that, the Subaru engine on my pressure washer has that same point, same with the Briggs Quantum 725ex on my lawnmower).

I will check the oil after I put the new coil on. I might just change it one more time to be sure I got as much gunk out as possible.

I did notice when starting this from a cold start it has a sticking valve sound initially. It clears up within 3-5 seconds, but I am wondering if that couldn't be part of my miss. Especially if they used only dino SAE 30 oil in this thing.

Hmmm... That settles it, I will put in some seafoam into the oil and run a tank of gas through it today. Then I will change the oil again and see how it is. Most certainly can't hurt.
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post #7 of 7 Old 04-07-2016, 10:48 AM Thread Starter
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I added the seafoam and ran a half tank of gas through it. It doesn't have as much of a "sticking valve" sound when re-starting it hot, but I have to wait until it cools down completely to be able to tell if it helped with a cold start.

Once I get the new coil in I will run another half tank of gas through it and change the oil while it is hot. Then I am done until the new guards and stuff come in for it in a few weeks.

I did get a chance to set the RPMs on my Brute 22" with a 725ex Briggs engine on it. It started out at 2720rpm... From the factory I have read it should be set at 2890rpm or thereabouts on this mower. I also read that the Quantum 725ex is spec'd for 3600rpm, but per federal guidelines you aren't supposed to run them faster than 3299rpm (to keep at 22" blade tip speed at or below 19,000fpm) and manufacturers can't set them above 3100rpm (so if you buy a replacement engine, it will be set at 3000-3100rpm or thereabouts, but a new mower itself will rarely be set to 3100rpm). I set mine to 3240rpm or so and am done. It sounds soo much better than before and I am hoping that it will mulch that much better too.
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