The above comments were all you got from that video? You might have the wrong tester??????? I would watch it all again my friend as I mentioned to you for free.
Surging motor on NEW carb!?
- Thread starter l008com
- Start date
l008com
Well-Known Member
Welp, "shockingly" the new coil had no change. So does replacing the coil and spark plug negate the need to get a gap tester since thats basically everything in the ignition system?
I also re-did the compression test with my drill to bypass the compression release and got around 95 to 100psi, which is good for a lawnmower right?
I also ran with the muffler off just to see, maybe its clogged. It ran the same with no muffler, just much louder. Still surging.
I also tried spraying small squirts of carb cleaner directly into the carb while running to see if it improved the way it ran, or made it worse. It made it worse, it basically killed the engine for a second or two then went back to normal. This suggests the engine is NOT running lean, does it not?
So the gas is good, the spark is good (?), the compression is good, the delivery seems good. If anything, it has more symptoms of being rich than lean. Is there a way to test rich-ness to confirm if it is or not. The 'manually choking" test and the "spray fuel in the carb" test are both pointing towards rich running, not lean running, as much as I understand them.
Also, how cross compatible do carbs tend to be? I could always try to pull one off another machine and see if it runs, if this still looks like a carb issue and not something inside the motor like a damaged cam or something.
I also re-did the compression test with my drill to bypass the compression release and got around 95 to 100psi, which is good for a lawnmower right?
I also ran with the muffler off just to see, maybe its clogged. It ran the same with no muffler, just much louder. Still surging.
I also tried spraying small squirts of carb cleaner directly into the carb while running to see if it improved the way it ran, or made it worse. It made it worse, it basically killed the engine for a second or two then went back to normal. This suggests the engine is NOT running lean, does it not?
So the gas is good, the spark is good (?), the compression is good, the delivery seems good. If anything, it has more symptoms of being rich than lean. Is there a way to test rich-ness to confirm if it is or not. The 'manually choking" test and the "spray fuel in the carb" test are both pointing towards rich running, not lean running, as much as I understand them.
Also, how cross compatible do carbs tend to be? I could always try to pull one off another machine and see if it runs, if this still looks like a carb issue and not something inside the motor like a damaged cam or something.
l008com
Well-Known Member
If by bowl jet, you are referring to the bolt/jet that holes the bowl on, then yeah i already tried swapping the original over, and that after soaking it in acetone for a week or more and cleaning it like I was sending it into space. No difference. But if you're referring to another part other than that, let me know.
StarTech
Lawn Royalty
Well it was just a thought....The only other thing I think is there wear on the governor. You could try adjusting the governor by placing a .010 feeler gauge between the throttle vane arm and its stop. But this just an experimental check. It has worked on Kohler Courage here.
You need air, fuel, spark (at the correct time) and compression. Find what you are lacking.
On an engine this old, I bet never been de-carboned. Your engine manual states roughly every 5-7 years to de-carbon. Meaning I bet a valve or two are not sealing and she is all carboned up inside.
Do you have a solid fuel flow AT the carb inlet? As in it WILL drain the fuel tank dry from full, into a glass jar? Try with the tank cap on. Fat flow of fuel tells you two things. One is you have good flow or not. Second is the tank cap vent is working or not.
7 pages now and lots of good suggestions. You've missed something.........
On an engine this old, I bet never been de-carboned. Your engine manual states roughly every 5-7 years to de-carbon. Meaning I bet a valve or two are not sealing and she is all carboned up inside.
Do you have a solid fuel flow AT the carb inlet? As in it WILL drain the fuel tank dry from full, into a glass jar? Try with the tank cap on. Fat flow of fuel tells you two things. One is you have good flow or not. Second is the tank cap vent is working or not.
7 pages now and lots of good suggestions. You've missed something.........
l008com
Well-Known Member
I may have missed something. And that something is that while both carbs surge in a similar way, one dies when you manually choke it (the new one) while the original one does have a spot where it smooths out, when almost totally choked, right before you kill it. I re-cleaned the original one and reinstalled it once I confirmed that it was still surging with the governor disconnected and me controlling the throttle with my finger. So this suggests that thew new carb is just bad. But I looked high and low, new and used, and there are no OEM or any non-chinesium brand carbs around, so like someone said much earlier in this post, I might just have to buy more cheap carbs until I get one that works well. Fuel flow is great, I know this because every time I switch carbs, plenty of fuel flows nice and freely. I'm hoping its not a valve/carbon issue, and I do get good compression when I did the compression test with a drill. And the replacement carb was only $9 so maybe I'll "splurge" on a $16 carb. I haven't had a lot of time to work on this thing but hopefully tomorrow I'll be able to poke around more. I'm trying to avoid taking the engine apart unless I have to. But if I have to I have to.
I do not see where you have done this.
You DO NOT need a tachometer for this test.
To eliminate the governor hunting instead of disconnecting the governor linkage I just simply manually hold the carb throttle at a fixed position and since it appears that your engine is suppose to run at around a constant 3600 rpm just manually hold the carb throttle at a fixed rpm of around 3600 rpm.
If the engine does not run smooth manually holding the carb throttle, it's not a governor problem, it's most likely a fuel issue which most generally is the carb, but can be air leak, bad fuel..
If it does run smooth holding the carb throttle in a fixed position manually and surges when you turn it loose, it's the governor control too senstive, which can be linkages, springs, etc
If you cannot get to and hold the carb throttle shaft manually at a fixed position, just hold the governor arm or it's linkage.
I noticed in a parts diagram that the mechanical governor linkage is item 202 and the rpms can be adjusted with such if needed.
You DO NOT need a tachometer for this test.
To eliminate the governor hunting instead of disconnecting the governor linkage I just simply manually hold the carb throttle at a fixed position and since it appears that your engine is suppose to run at around a constant 3600 rpm just manually hold the carb throttle at a fixed rpm of around 3600 rpm.
If the engine does not run smooth manually holding the carb throttle, it's not a governor problem, it's most likely a fuel issue which most generally is the carb, but can be air leak, bad fuel..
If it does run smooth holding the carb throttle in a fixed position manually and surges when you turn it loose, it's the governor control too senstive, which can be linkages, springs, etc
If you cannot get to and hold the carb throttle shaft manually at a fixed position, just hold the governor arm or it's linkage.
I noticed in a parts diagram that the mechanical governor linkage is item 202 and the rpms can be adjusted with such if needed.
Last edited:
Auto Doc's
Lawn Addict
The governor only has one job and that is to keep the engine from running wide open above 3600 RPM and the engine blowing itself apart internally.
This problem is with the carburetor not balancing the air fuel mixture properly.
Most new replacement carburetors have an idle bleed jet that is often undersized and the engine gets disrupted air flow internally to properly atomize the fuel mixture.
James Condon "Mr. Generator" has a lot of good You Tube videos dealing with this surging issue and he discusses how to correct it on most carburetors. Carburetors basically operate the same on small engines regardless of being a horizontal or vertical crankshaft design.
This problem is with the carburetor not balancing the air fuel mixture properly.
Most new replacement carburetors have an idle bleed jet that is often undersized and the engine gets disrupted air flow internally to properly atomize the fuel mixture.
James Condon "Mr. Generator" has a lot of good You Tube videos dealing with this surging issue and he discusses how to correct it on most carburetors. Carburetors basically operate the same on small engines regardless of being a horizontal or vertical crankshaft design.