6.5 Intek engine surging

I purchased a Cyclone Rake leaf vacuum 4 years ago. It is a magnificent piece of machinery with one problem, the engine. The first year it ran great but started to surge towards the end of my two week vacuuming chore. Put it away, got it out the next year, wouldn't start. I removed and cleaned the carburetor, reinstalled, and completed my two week chore, surging worse towards the end. Put it away, got it out the next year, wouldn't start. Completed one more carburetor cleaning, reinstalled it and completed my chore, engine struggling. This year I opened the gas tank and found milky white gas. It turns out that the inside of the gas tank was galvanized and much of it had dissolved in the gas. This engine had been stored in a dry climate controlled shed when not in use. Some of the zinc was in the form of particulates and some was much smaller. I don't think the engine wants to run on a gas/zinc mixture. The tank was cleaned by filling it with a gallon of vinegar for 24 hours and hosing it out, filter installed because existing screen is a joke. The main jet is probably too small, there is no idle mixture adjustment. It runs now. Will drain tank at end of season. Hope this helps someone.

Were you storing the engine with gas in the tank ??????

Even though you were not doing that I would take it out once a month like a genny and crank it up and run fuel thru it......

Almost every year I had to to go to a friends house and clean his carb on his genny.... Not anymore, he took my advice and runs it at least once a month ......

First, drain the old gas out of the tank. Old gas destroys those carburetors.

Running the engine for a couple minutes occasionally would keep the gum from building up
Add fresh gas and add some Seafoam to the tank. Then let the engine run it through. There is a chance the engine might clear up and start running better. Use ethanol free gas if you can. It might cost more, but it will save you a lot of headaches.

Make sure the float and the needle in the carb is moving freely and sealing correctly. I've had some where they don't open all the way and the engine starves for fuel.

Another reason it might be surging it because of a vacuum leak caused by a leaking gasket. Examine the gaskets mating between the carburetor and the intake manifold and the cylinder head. Gaskets are cheap.
While your at it, it would be a good idea to check the clearances in the valves. It should be .005" intake and .007" exhaust. This is optional.

If all else fails, then you might have to get a new carburetor. Aftermarket carburetors are cheap on Amazon or Ebay and they work well most of the time.