Tecumseh Snow King snowblower engine surges, even after new carb

I have a 10hp Tecumseh Snow King snow blower engine that surges. Instead of rebuilding the carb, I found you can order a new one (Oregon brand) for about $25 on Amazon. So I did that and installed it. Still surges, although it's slightly better.

Also, I held the linkage still between the governor and carb and it still surged, so that should rule out the governor linkage as a problem, I believe.

Gas is only a month old and was treated with Stabil when I first got it, so that should rule that out.

What else could be causing it to surge? Could the vacuum tube that goes to the carb be causing that if it's too loose on that little inlet on the carb? It stays on there snugly but the tube is a bit expanded where it connects on the carb.

Anything else I should check?

 

Pretty easy to check for vacuum leaks everywhere. Just spray carb cleaner or WD40 around all the mating surfaces and see if the surging evens out. If it does, ya got your leak.

If you can't come up with an external leak you've got a lean condition through the inside of the carb - either a fuel restriction going into the carb or the main jet is too small or a metering screw needs adjusted.

If you have any of the above and you choke it the surge should even out.

 

Thanks for the reply. Didn't realize it was that easy ... that carb cleaner or WD40 would temporarily seal the leak to help you figure it out!

If that little vacuum tube that goes from the primer bulb to the carb isn't air tight, could that definitely cause surging?

The only other tubing going to the carb is the fuel line. Is there any where else I should check for air leaks?

 

No, it works like this. The surging is typically caused by a lean mixture of fuel to air. They call it "hunting". The lean mixture can be caused either through a plugged fuel supply or too much air from an air leak = vacuum leak. When you spray the carb cleaner/WD40 it doesn't seal anything, it feeds more fuel into the system to balance out the lean mixture.

If you get those results you know where the leak is and you can tighten it down or replace a gasket, whatever it takes.

 

When you replaced the carb, did you clean out the old gasket and the two mating surfaces before adding the new gasket?
I've seen this a few times where the carb either didn't have a gasket or it was cracked and starting to leak.

 

Yup, replaced that gasket, but thanks for that tip.

 

Before doing the vacuum leak check with WD40, I snipped off the end of the primer vacuum line, where it was expanded over the carb inlet and put the newly cut tighter end on the carb inlet for the vauum line. It's now running good so far, but I haven't had time to test it for an extended period. Could that be the cause of the surging ... a leaking vacuum line that goes from the primer bulb to the little inlet on the carb?

 

Im no expert but I would think that any vacuum leak going into the carb inlet will cause issues such as the surging you are experiencing. Is there a leak at the bulb itself?

Paul

 

No leak in the bulb, just where the primer vacuum tube connected with the carb. The end of the tube was a bit stretched out, so snipped it off to make a tighter end to fit over the carb inlet.

 

there is also a static governor adjustment to do whenever carb has been removed and put back on. Common to have to do that to stop surge on briggs and had it on a tecumseh once as well