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Discussion Starter #1 (Edited)
I got this thing given to me and I'm beginning to see why. I'm near ready to kick it to the curb. It runs like crap. Runs a little better when choked. I've had the carb off a couple of times looking for a blockage. Main jet is clear. Carb was soaked for 48 hours to clean. It's getting fuel. Removed fuel line and filter and replaced with another with no change. This should be simple there's not much to it. It's a Honda HS35.

 

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A lot of small engines are designed to run with air cleaners. The air cleaner provides some flow resistance.
You reminded me that I have to get my snow blower up from under my deck.
 

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I bought a generator that had a similar problem, it was cheap and almost brand new but would only run properly with almost full choke. Without choke it constantly surged. I must have had that carb ( engine is a Honda GX270 clone) apart so many times I could do it in the dark and always it was the same. I too was ready to throw the thing down the hill, I cursed the smarmy mongrel that sold it to me, and his sisters and his mother and his neighbors....his neighbors mother....
I finally ordered a new carb online, it looked the same but didn't quite fit because of the air filter arrangement. Oh well, I started swapping jets and other bits to see if things would improve-nope still surging away. According to my research, 99% of the time surging is caused by lack of fuel, and thus it was it the end. There was a little plastic plug on the side that seemed to have something to do with directing suction to an idle jet, when I swapped the only-slightly-worn looking O rings on it for the ones on the replacement carb-bingo! Instant success, the bloody thing just purred away no problem at all.
Maybe, just maybe, you have a similar problem.
Best of luck with it!

iddy
 

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With the tightening of emissions many small gas tools are getting harder to keep running properly. They need a richer mixture then the carb is set to supply out of the box.
 

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Discussion Starter #5
Thanks for the replies. My engine is a G150. Not much to the carb and from my understanding the carb is only used on this snowblower. There are no plugs on the carb body.

It's running too rich. Backfires through carb and spark plug is dry black. Tried a different plug with same result. Float level appears to be good and isn't adjustable. No apparent air leakage around carb base.
 

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Discussion Starter #6
A lot of small engines are designed to run with air cleaners. The air cleaner provides some flow resistance.
You reminded me that I have to get my snow blower up from under my deck.
It doesn't so much have an air cleaner. Not too much dust blowing around in the winter. All it has is a metal shield with a bit of very coarse wire mesh in it. Putting it on makes no difference in how it runs.
 

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I have an Ariens, pretty large one. Mine has no air filter-pretty sure few do. I have to "play" with the choke every time I use it. I think your issue is def. Related to fuel...type/flow/octane/additives, etc.
I learned I have to drain the gas each spring,use Seafoam and put in Mobil 89 octane. If I change any of that, I have issues with it.
Good luck!
 

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I have a big Tecumseh powered snowblower, I think it's 11hp? Surges like crazy too. Weird part is that when it's under load it smooths right out! I read something on the web about cleaning up the jet to fix the problem, but I haven't gotten around to it yet. I know you've already cleaned your carb so it's probably not that. Drives me nuts with the surging! I've also got a little single stage from Crappy Tire. It has a chinese Honda knock off engine on it and it purrs like a kitten!

I've also read that the governor can cause issues, but I haven't looked into that much.

Be nice if we didn't get all this snow in the winter, I'd glady trade in my blowers for more lawn mowers anyday! :)
 

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Discussion Starter #9
I've also read that the governor can cause issues, but I haven't looked into that much.
I was going to post yesterday but got busy. I'm actually thinking that it is a governor problem. I have two identical snowblowers. One I've owned since new and this one that was given to me. Yesterday I hauled mine out and put some gas in it. Always starts on first tug as does this 2nd one.

Started on choke and after about 30 second I opened the choke. Right away the governor linkage went way over and the settled in at a steady RPM. The second unit the governor doesn't move. I do recall it moving on one of the many occasions I've now tried this thing but right now it's not moving unless I move it. When I do I can get it to run steady. Had the thing stick at what sounded like 6000 RPM. Thought it was going to blow up.

So looks like I need to take that engine out of there and see what's going on. More projects.
 

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When I set my snow blower to run right in the dead of a New England winter, it runs way to rich at temps above 30F. (Your mileage may very.)
 

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For some reason I don't get all the new posts. Just to confirm:

1) Has this engine run properly for you before this problem started?

2) All good, new fuel, completely drained, right?

3) You mentioned apparently rich, black plug but backfiring through carb. Correct? Is it a continual, regular popping or intermittent and crisper sound? If continual popping you may have a partially stuck valve, burnt valve, etc. The intake pulsations can make for some weird jetting effects in small engines. Even tight valves can be a bit odd.

4) Surging is usually lean so odd that the two are in combination. You did mention that the governor will move by hand?

5) You mentioned cleaning the carb. Would you mind relating how you did the cleaning? Did you use high pressure shop air in the cleaning to blow out passages?

6) If is rich and ran well prior to this, most likely fuel level or plugged air bleed to the emulsion tube. Did you run jet drills through the holes in the main jet and emulsion tube? I've found quite a few will build up with chalky stuff which even the ultrasonic cleaner sometimes won't remove.

Does it have a bowl drain plug? Many of these small carbs have an 8mm or 10 mm head bolt as a bowl drain plug. One can hold a soft PCV hose against the hole (plug out) to see where the fuel level actually sits. If it's flooding, the level will be above the bowl gasket line in most cases. I've often found some lacquer or other deposits in the needle valve bore which keeps the needle from moving up into the seat.

In a pinch, why not swap the two carbs. to see if the problem stays with the engine or the carb.

HIH

I was going to post yesterday but got busy. I'm actually thinking that it is a governor problem. I have two identical snowblowers. One I've owned since new and this one that was given to me. Yesterday I hauled mine out and put some gas in it. Always starts on first tug as does this 2nd one.

Started on choke and after about 30 second I opened the choke. Right away the governor linkage went way over and the settled in at a steady RPM. The second unit the governor doesn't move. I do recall it moving on one of the many occasions I've now tried this thing but right now it's not moving unless I move it. When I do I can get it to run steady. Had the thing stick at what sounded like 6000 RPM. Thought it was going to blow up.

So looks like I need to take that engine out of there and see what's going on. More projects.
 

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Discussion Starter #12
Normk.

I just spent the last 1/2 hour replying to your questions only to have my iPad freeze up when I went to post it. Lost everything. I'll have to get to it again later. I do have the engine on the bench and plan to look at the governor internals.

Here is a picture of the carb for reference. It's a pretty basic unit. Main nozzle doesn't come out like they show. At least not that I can see and I don't want to break anything. Parts are hard to get for this 25+ year old machine.

 

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People often wonder what are all the components on computer and processor mother boards. The operation of these things was explained by a friend as follows: "That little square box over there is what runs the whole thing and does all the processing. All the other stuff is what senses and calculates when is the worst time to have it crash so as to cause the most trouble." That seems to fit the experience. ;-)

If you haven't removed the Main Jet #15, then you haven't remove the emulsion tube #9, right? That's likely the problem as the air inlet holes in the sides introduce air into the fuel flowing up inside the tube.

Air flow through the carb's venturi creates a low pressure area in the carb allowing atmospheric pressure in the float bowl to force fuel through the main jet and up the inside of the emulsion tube to exit as a spray into the air flow in the venturi.

Air is introduced into the sides of the emulsion tube through the holes in order to break-up/emulsify the fuel rather than to have a solid stream of fuel. The fuel is a stream of fuel with air bubbles which allows the fuel to more readily scatter/distribute into the air flow.

If the air bleed holes are restricted or plugged, the amount of air entering the fuel is reduced which results in a rich mixture. An additional problem is the more solid stream of fuel makes for larger fuel droplets which don't start burning as soon or burn as well.

You will likely need to extract the emulsion tube and clean out the holes but take care not to increase the size of the holes.

The idle pilot jet for many bike carburetors is a combination of jet and emulsion tube with even tinier holes.

If one visualizes the fuel flow through main jet and the effects of the air holes in the emulsion tube, one can better understand the effects of jetting changes. People often wonder why idle mixture screw adjustments become ineffective after the mixture screw is turned out 2-1/2 turns or so. If one recognizes the effect of the emulsion tube's fuel passage and that of air entering, one can see that once the screw is out past a certain point that, further opening of the screw becomes less effective in restricting flow in comparison to the other factors.

Carbs are like camshafts, far more complicated in operation than most people will accept but one can get by in the repair side without bothering with the finer aspects of the engineering unless one moves outside of the design intentions.

I'm certain that you know all of this but thought it might be useful to someone else following the process.

Sometimes my ultrasonic cleaner will clear the tiny passages in emulsion tubes and jets but sometimes the jet drills and pin vise have to do the work.

FWIW, once in a while one encounters a carb which has a plugged internal passage which requires drilling out some of the gallery plugs. I just did some carbs off a VF750S Honda which had been sitting since 2006 and had some blockage requiring reaming inside the galleries.

Mercury outboards (and lots of others) have a similar issue but almost 100% requires removing a Welch plug to clear a pocket in the idle circuit.

HIH
 

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Discussion Starter #14 (Edited)
I did remove the main jet but not the emulsion tube. When I soaked the carb I did have the jet removed.

I did get the case opened up this morning to check the governor. I didn"t expect to find anything wrong inside but had read on the Net that the governors were a problem. I can't see anything wrong with this one. Everything moves freely and is intact.

 

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Discussion Starter #15 (Edited)
Pulled the carb again and was able to remove the "emulsion tube" (main nozzle). It was clean and none of the holes were plugged. I was able to pass I believe a #2 tip cleaner wire easily through the holes.
 

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Good stuff on the emulsion tube. Did you blast high pressure air through it also? Had to chuckle today when walked into a small engine shop in search of a fuel pick up filter and there was your carb on the counter. Since you got the emulsion tube out and blew out tube and emulsion tube bore, it seems like you must have come back for the carb.

A bit of a drive to take the carb to Monte's Small Engines but since both are in Canada, how much of a drive can it be? ;-)

Funny, seeing the same model used carb, though.

Governor: if all moves freely and no broken springs or big slop in things, that's about all I can recall running into on small engine governors. They're usually trouble free. I've seen a few which had a weak spring on the carb linkage which made the RPM hunt but don't know why. Just know that putting a finger onto the linkage or a new spring solved.

Hoping the clean did the job.

Did you try Chevron Premium in case the high alcohol was the problem?
 

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Discussion Starter #18 (Edited)
My current status is I have this POS back together. Will fill it back up with oil in morning and hook up the gas tank on the bench to see what happens. If it doesn't run I haven't a clue what to do next.

Norm: You should have picked up that carb for me, lol. Yes I blew everything out with air, more than once. Unfortunately Chevron fuel is not available in Alberta. When I travel in the USA I try to use Chevron whenever possible. The Premium fuel here is ethanol free.

Jeff: I've pretty well overheated Google over this thing. Seems like my engine and carb are specific to this snowblower. The engine is a G150. I do have governor adjustment instructions and I think I have this set up correctly. We'll find out in the morning. This could make for a bad day.
 

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Discussion Starter #19
Going to try and get this answered. Red type following the questions.

For some reason I don't get all the new posts. Just to confirm:

1) Has this engine run properly for you before this problem started?

Don't know. It's new to me and I have no history. Apparently was "serviced" and then not used for 3 years.

2) All good, new fuel, completely drained, right?

Fresh, premium fuel.

3) You mentioned apparently rich, black plug but backfiring through carb. Correct? Is it a continual, regular popping or intermittent and crisper sound? If continual popping you may have a partially stuck valve, burnt valve, etc. The intake pulsations can make for some weird jetting effects in small engines. Even tight valves can be a bit odd.

I think it's running rich because it only runs when choked. The popping is intermittent and crisp. If you have your face to close to look you get sprayed with gas. Further to this it doesn't have the correct NGK plug in it. HAs an Autolite which crosses over but comparing it to the NGK in the other machine it would appear that the plug reach is less with the Autolite. I'm having a hard time sourcing the correct NGK plug. Found them on Amazon and ordered but so far they haven't shipped.

4) Surging is usually lean so odd that the two are in combination. You did mention that the governor will move by hand?

Yes governor moves by hand and operates throttle plate. As you already know I've had it apart to check governor which seemed okay.

5) You mentioned cleaning the carb. Would you mind relating how you did the cleaning? Did you use high pressure shop air in the cleaning to blow out passages?

Carb was soak in Pine-Sol for 36 hours. Came out shiny clean. Blew out with air.

6) If is rich and ran well prior to this, most likely fuel level or plugged air bleed to the emulsion tube. Did you run jet drills through the holes in the main jet and emulsion tube? I've found quite a few will build up with chalky stuff which even the ultrasonic cleaner sometimes won't remove.

I didn't then but have now

Does it have a bowl drain plug? Many of these small carbs have an 8mm or 10 mm head bolt as a bowl drain plug. One can hold a soft PCV hose against the hole (plug out) to see where the fuel level actually sits. If it's flooding, the level will be above the bowl gasket line in most cases. I've often found some lacquer or other deposits in the needle valve bore which keeps the needle from moving up into the seat.

There is no needle valve. The jet controls the fuel flow and the governor the speed. Float is not adjustable and I measured it to be on spec.

In a pinch, why not swap the two carbs. to see if the problem stays with the engine or the carb.

It may come to that but I hate taking stuff off of a good running machine. They don't make it easy to get at either although I've done it so often I'm pretty quick.
 

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You posted:

"3) You mentioned apparently rich, black plug but backfiring through carb. Correct? Is it a continual, regular popping or intermittent and crisper sound? If continual popping you may have a partially stuck valve, burnt valve, etc. The intake pulsations can make for some weird jetting effects in small engines. Even tight valves can be a bit odd.

I think it's running rich because it only runs when choked. The popping is intermittent and crisp. If you have your face to close to look you get sprayed with gas. Further to this it doesn't have the correct NGK plug in it. HAs an Autolite which crosses over but comparing it to the NGK in the other machine it would appear that the plug reach is less with the Autolite. I'm having a hard time sourcing the correct NGK plug. Found them on Amazon and ordered but so far they haven't shipped."

If it only runs with the choke, that means it's lean = not enough fuel to air = needs more fuel. That's opposite for what I was considering/suggesting diagnosis. Will wait for your report on running but need to investigate insufficient fuel/too much air causes otherwise.

The needle valve is the fuel level control valve which is operated by the float. Your carb has one but the needle seat is part of the carb body rather than a replaceable part as in the KLR's and more sophisticated carbs.

My suggestion that the needle may be hanging in the needle seat bore would still be a possible cause for lean or rich.

Restricted fuel flow from the tank, restricted carb fuel inlet, low float bowl fuel level, intake air leak, no or wrong air filter for engines jetted for air filter are all common lean causes. No air filter would fit your symptoms, as would jetting for a generator or water pump using this carb. You suggested that this model of snow blower doesn't use an air filter so jetting might be different from the same carb on an application which does. Same symptoms = lean.

Will the engine pick up a load for a minute or two + with choke's help? If so, the fuel flow is likely OK but I do like to pull the bowl drain to see that the fuel flow volume is significantly greater than the engine might use.

I think misspoke in an earlier post and referenced item #8 as idle pilot jet which was clearly wrong as it is the float needle valve. Was thinking of the main circuit and didn't pay enough attention, sorry.

A possible is the heat isolation block, item #10. If some of those are installed in the wrong orientation, they create a vacuum leak into the intake. That would fit the lean symptoms.

You might hold a piece of PVC hose onto the bowl drain hole and turn on fuel. With the hose looped upward, the fuel should be about at the bowl gasket level. If much lower, the fuel level is too low. Maybe wrong needle valve? Some needle valves can fit into the carb without being clipped into the float valve's ears which makes for a very low fuel level. I think these Honda needles slide into the float so don't go into the needle seat with float underneath the needle?

I was confused by the popping back when the condition was rich.
 
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