small engine surging

Zachary Hoyt · Nov 15, 2011

I bought a fixed speed (3600 RPM) Tecumseh generator engine from Surplus Center for my planer. It is a 10 hp. It was sold as new but it has probably been sitting for a few years, I would guess. I mounted the pulley on the crankshaft but I have not hooked up the belts. The engine will run about 5 seconds on a cold start and then it begins to surge and the governor control rod moves back and forth. On the Briggs engine on our sawmill I have twice over the years had it do that and both times it has been a little speck of crud in the carb needle and seat area, or at least when I have cleaned that area out it has run well again. I am wondering if I should look at that on this engine or if there is some other problem I should check on. The engine is new and unmodified, the only thing I changed was to slide the pulley on the crank and tighten it down. Any advice will be much appreciated. I am running 30W oil for now, air temp is around 50 degrees F.
Zach

rustyfarmall · Nov 15, 2011

(quoted from post at 08:09:04 11/15/11) I bought a fixed speed (3600 RPM) Tecumseh generator engine from Surplus Center for my planer. It is a 10 hp. It was sold as new but it has probably been sitting for a few years, I would guess. I mounted the pulley on the crankshaft but I have not hooked up the belts. The engine will run about 5 seconds on a cold start and then it begins to surge and the governor control rod moves back and forth. On the Briggs engine on our sawmill I have twice over the years had it do that and both times it has been a little speck of crud in the carb needle and seat area, or at least when I have cleaned that area out it has run well again. I am wondering if I should look at that on this engine or if there is some other problem I should check on. The engine is new and unmodified, the only thing I changed was to slide the pulley on the crank and tighten it down. Any advice will be much appreciated. I am running 30W oil for now, air temp is around 50 degrees F.
Zach

Does it have the adjustment screw on the carb bowl? If so, you can usually stop the surging by adjusting that screw slightly either in or out. If it is a speck of crud causing the issue, adjusting that screw will usually dislodge it. It is also a possibility that since the engine is new, it will require a few adjustments to make it run smooth. If there are no external adjustments, then you'll need to take the carb apart.

Old Roy · Nov 15, 2011

If being new I wonder if it isn't broke in .. I mean it is set up to pull a load and engine is doing a search. my Briggs on my Gen does that till I put a load on it .

RGMartin · Nov 15, 2011

Hook up the belts and see if it runs smoothly.

Many cheap generator spec engines use a light flywheel to save cost because the armature acts as a flywheel.

Your planer head may help if it is an inertia issue.

Kentb of SWMO · Nov 15, 2011

Lean idle mixture. First what grade fuel are you using? If 87 try 89. If you have a idle mixture adjustment try that BUT if you have the later fixed jet carb, you need to do a little super tuning. I worked on a very late production verticle shaft engine Both jet fixed. It was running lean on both sides. I had to drill out both the idle and high speed jets. If ti is the older carb with a adjustment and the adjustment does not work, likely you idle mixture passage is plugged. Tecumseh carbs do not like water. Even condensation is enough moisture to plug their idle mixture passage.

Kent

John M · Nov 15, 2011

Completely different situation, but our old Johnson engine on our old boat was bad about fouling plugs, constantly needing the carbs rebuilt, etc., etc. Dad finally had an old Navy mechanic take a look at it. After some work, he went to the lake with it, adjusted the carbs on it, and told us whenever we were done getting it on the trailer, before we pulled it out of the water, disconnect the line from the tank, then shut it off when it just started to speed up. Said something about it burning off the oil that had accumulated in the cylinders and carbs or something to that effect. I may have it all backwards, but we never had any further trouble with it for the 7 or 8 years we owned it after that.

John M · Nov 15, 2011

SORRY!!!! This was suppose to be down in the "Theory" post!

S2710 · Nov 15, 2011

I have a 10 horse Tecumsch on my gen. set. It ran that way but when you put a load on it it ran OK. I put a gallon of gas in the tank and added a half of a can of Sea Foam. Then I hooked it up to a load and ran it until it ran out of gas. Put fresh gas in and now it runs smooth.

Bob

Zachary Hoyt · Nov 15, 2011

I took a couple of pictures of the carb since I am not even sure
what I am seeing. I tried hooking up the belts and that made it
surge on a slightly longer cycle, so it is a little better. There is a
screw at the top with a spring on it that does not seem to be
attached to anything that I can see, there is what looks like a screw
with a plain flat head lower down just above the bowl, and there is
of course the screw in the middle of the carb bowl that holds it in
place. I am wondering if the blank screw is the adjustment and if
so how I might be able to turn it. Thank you all for your help.
Zach

rustyfarmall · Nov 15, 2011

Zach, on the older carbs, that screw on the bottom that holds the bowl on USED to have an adjustment screw in it. Just like the load or high speed idle adjustment screw on your Farmall H or M. I'm guessing that adjustment screw is not there on these newer carbs thanks to the EPA. I see nothing else in the pictures that looks like it would accomplish the same thing.

Az. Peapicker · Nov 15, 2011

In the picture ,the area where the black cap is should be an adjutment screw. Take the cap off & open the jet up just a little counterclock wise . This should help.

John

Anonymous-0 · Nov 15, 2011

That's very similar to the carb I have on my snow thrower engine. That screw on the top that doesn't do anything would adjust the low idle speed on a variable speed engine.

I don't think it is adjustable but there should be two or three alternate holes in the sheet metal arms where the wire from the air baffle hook up. You might try a different one. I put mine together wrong and it lopes pretty bad unless the augur is full of snow.

I'd second the comments about higher octane fuel and Sea Foam. All you can do besides that is blow it out with carb cleaner. If you are adventurous, you can bore out the fuel passages.

MarkB_MI · Nov 15, 2011

Typically caused by a blocked idle circuit. If you can't clean out the carburetor passages, a new carb may be in order.

WJD · Nov 15, 2011

I had a similar problem on a lawnmower this past summer. After lots of tinkering decided to switch from gasoline/10% ethanol blend to 100% premium grade gasoline.

Problem went away. May or may not be your problen but small engines don't seem to like ethanol.

WJD

Neb Super H · Nov 15, 2011

It is one of 2 things. Blocked or lean idle jet/circuit or mis-adjusted governor. To fix the governor, you will need to bend the metal tab that the governor spring is hooked to till you get it to disappear.

ShadetreeRet · Nov 15, 2011

The screw on the side of carb should be the low speed adjustment, the screw in the bottom is high speed adjustment, The float bowl is held on by the nut that the screw goes through. Try turning bottom screw CC a little at a time and see what happens. If nothing try going the other way. A properly adjusted engine should run smoothly whether under a load or not. If you received a parts list or instruction booklet with it, that should help a little. Good luck.

gymo · Nov 15, 2011

The screw under the black cap is a pilot jet remove and clean out the very tiny hole in the middle.

bill mart · Nov 15, 2011

rg,thats what I was thinking too. Bill

gab · Nov 15, 2011

I,ve got a 10hp tecumseh on a generator, looks just like your carb. The top screw with spring is idle speed, doesn't do anything on a fixed speed gov. The screw just above the bowl is the idle mixture adjustment. If there's a nut on the bottom of the bowl, it's a fixed jet like mine. If there's a screw on the bottom try backing it out a hair. I'm guessing your trouble is in that bottom jet, doesn't take a very big speck of any thing to screw up one of those carbs.

VicS · Nov 15, 2011

I bought a 10 hp Tec, gen also It had set in the store for 3 to 5 yrs. Bought it cheap. Bottom line power went out last winter. I had put syn oil in it but had never put any gas in it. Filled it with gas and it started, and ran just like yours, yes all the gas here has alcohol in it. Took carb cleaner and squirted up jet. Still surged would not quit til I put choke on a tad. Found a real light spring which just pulls choke on a little, just a 1/4 of a notch. Power went off last night, Started on first pull and ran perfect. Not a very kosher fix, but it works. I think if the air cleaner gets a little dirty I can take the little spring off the choke. Vic

small engine surging

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Member

Well-known Member

Well-known Member

Member

Member

Well-known Member

New User

Well-known Member

Well-known Member

Well-known Member

Similar threads