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First post! I have a GC160 water pump that I got for cheap since the previous owner left water in it and the pump housing cracked due to the water freezing. I’ve cleaned up the engine and it is in great condition. The carb was spotless but I still decided to clean out all of the jets and replace the fuel hose to the carb because it had some small cracks. I’ve since taken the seized water pump off of the shaft and bought a replacement water pump. I also did a typical tune up (oil change, fuel filter, air filter, and spark plug).

The problem that I’m having is that it starts up perfectly but can’t run without choke. It surges trying to find idle and it backfires (after fire). It runs really well with about 80-90% choke and poorly with full choke or no choke. Before I took the broken pump off the engine ran perfectly and didn’t have issues. I haven’t adjusted the governor arm and I didn’t mess with the pilot screw since it had the EPA block on it. I’m thinking that the issue could be due to not having a load. Does that sound about right? I ideally would put the new water pump on and test it but everything is frozen (-30 DEG F) and I hear that the pump shouldn’t be run dry.
Is it likely having an issue running without choke because there’s no load on the engine? And if so, is the only way to test it to put the pump on? Or can the governor be adjusted to operate at no load for testing purposes?
Thanks!

surging is usually a lean running engine, meaning too much air, or not enough fuel.
try turning the pilot screw out as much as the EPA allows you, a little at a time and see if it will smooth out.
were all of the carb gaskets in good shape when you removed it and put it back on?

I replaced all of the gaskets since there was only the bowl gasket and the gasket for the bolt on the bottom of the bowl. I sprayed out all of the jets with carb cleaner and took out the main jet and main nozzle and they were spotless. I suspected I missed something the first time so I even cleaned it out a second time. I replaced the air filter gasket, the carb gasket, the and insulator but used the existing insulator gasket and air guide (names from the service manual). The air guide and insulator gasket are in okay shape but aren’t perfect.

I’ve since cut off the EPA tab which gives me complete adjustment but it didn’t seem to make much difference. That being said, it’s also extremely cold outside and I didn’t spend too much time messing with the pilot screw. The EPA tab only allowed for about a 1/4 turn adjustment and didn’t make any difference.
Would the water pump not being on the shaft not make any difference? I’ve read that could be a factor especially since the carb was so clean and the engine is in great condition. The intake valves look spotless and the engine has great compression. I haven’t taken a look at the valve clearances yet but I’m guessing they’re fine.

Without anything connected, the engine is only running on the pilot circuit
Once you hook something which puts a drag on the engine the governor allows the throttle to open fully so now the engine is running on the main jet as well.
Inside the tank should be a filter which may be clogged
The tap should have a replacable rubber seal that is prone to swelling and of course there is a sediment trap under the tap ( where fitted )

I did replace the fuel strainer that goes from the tank to the fuel pump. That’s good to know about it only using the pilot circuit. So since it’s not using the main jet it’s running lean and causing the surging? And the only way to fix this is to put the water pump on?
I’m not sure exactly what you mean about the tap. The only other o-ring on the carb is the drain screw o-ring that I can see from the diagram. I replaced the other two. I also cleaned out the pilot jet by removing the large screw on the top and blowing it out with carb cleaner. It didn’t look clogged. I didn’t remove the pilot screw that is used to adjust the mixture. My carb has the intern pilot jet and not the external one with the black plastic piece.

If it runs fine with half choke you are getting plenty of fuel into the carb. You either have an air leak or more likeley a blocked idle circuit.

From your first post.

Before I took the broken pump off the engine ran perfectly and didn’t have issues.

I would clean the carb again and be sure to clean the pilot jet.

Looks like the USA versions are a bit different to the Aust versions
Ours have a tap incorperated into the carburettor
Just checked Parts Nation with 5 different versions and none had taps like ours do

Hammermechanicman said:

If it runs fine with half choke you are getting plenty of fuel into the carb. You either have an air leak or more likeley a blocked idle circuit.

From your first post.

Before I took the broken pump off the engine ran perfectly and didn’t have issues.

I would clean the carb again and be sure to clean the pilot jet.

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That’s why I suspect that the pump had something to do with it. I cleaned the pilot jet two times and it was spotless and clear before I even cleaned it the first time. That’s why I suspected the no load was causing this issue. Where could the air leak be coming from? I replaced most of the gaskets with the only two being the big air guide one and then the insulator gasket. Or could it be from the breather side of things? The breather gasket looked rough and like someone had tipped it. Had a light coat of oil on it.

bertsmobile1 said:

Looks like the USA versions are a bit different to the Aust versions
Ours have a tap incorperated into the carburettor
Just checked Parts Nation with 5 different versions and none had taps like ours do

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That is why the spec number and serial number is needed most as there is several dozen different engines that are label GC160. There is even five different base GC160's.

StarTech said:

That is why the spec number and serial number is needed most as there is several dozen different engines that are label GC160. There is even five different base GC160's.

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GCAHA-5606565 QHA* is my model. It’s part of the BE brand WP-2050HL.
Thanks for all of the help guys! I hope we can get to the bottom of this.

Please double check the Honda model number. Can’t find anything with a serial of 5606565.

bertsmobile1 said:

Without anything connected, the engine is only running on the pilot circuit
Once you hook something which puts a drag on the engine the governor allows the throttle to open fully so now the engine is running on the main jet as well.
Inside the tank should be a filter which may be clogged
The tap should have a replacable rubber seal that is prone to swelling and of course there is a sediment trap under the tap ( where fitted )

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So is there anyway to make the engine run off the main jet too without putting the pump on? Would a governor adjustment work?
Also, is it fine to dry run the pump just for testing? I don’t want to damage the seals but I really have no way to test it

Use your finger to open the throttle butterfly
Do it slowly because these engines do not handle reving above 5000 well at all

bertsmobile1 said:

Use your finger to open the throttle butterfly
Do it slowly because these engines do not handle reving above 5000 well at all

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I used my finger to open the throttle and it sounded great. I basically added a light resistance to the governor arm and it wasn’t backfiring at all. I tried adjusting the pilot screw and it didn’t seem to do much. It did backfire more when it was leaner but it didn’t get fixed by simply adjusting pilot screw. Something bad did happen... the pilot screw broke off even though I was really gentle with it and only used the tips of my fingers to turn the screwdriver. The head sheared off the shank so either need to get a new screw and somehow remove the one stuck in the carb or just get a new carb.
Obviously it’s surging because of an improper air fuel mixture, but I do suspect the since the machine isn’t loaded the governor arm is having a hard time idling. What do you guys think?

I can confidently say that it was not the original carb. I did get a new carb along with a complete gasket kit. The issue was because of an air leak caused by my incompetence. I had the carb insulator flipped so there was an air leak which caused a lean condition. I also suspect a couple of my other gaskets were leaky. The original carb was spotless and if the mixture valve didn’t break off I suspect it would have also worked perfectly.
Thanks for the help!

AKTad said:

I can confidently say that it was not the original carb. I did get a new carb along with a complete gasket kit. The issue was because of an air leak caused by my incompetence. I had the carb insulator flipped so there was an air leak which caused a lean condition. I also suspect a couple of my other gaskets were leaky. The original carb was spotless and if the mixture valve didn’t break off I suspect it would have also worked perfectly.
Thanks for the help!

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Mechanic's Rule of Thumb: The last thing you worked on is the first thing to break.

Richard320 said:

Mechanic's Rule of Thumb: The last thing you worked on is the first thing to break.

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Really? for me it is more like Whack-a-mole. HA!!