Question about Yamaha Ef1000is Gas-powered Inverter Generator
Make sure there are no vacuum leaks on the engine manifold side of carburetor. There are 3 o 4 pieces on the engine side so inspect well.
If no leaks on engine manifold side then likely there's a blockage somewhere in the carburetor high speed circuit. Most economical solution is chinese knock-off for ~$20 US delivered.
If you can't find a cheap replacement then you'll need to do a deeper clean of carburetor by removing welch plugs and submerge in carb cleaner. You will need new welch plugs (kit) and likely kit will cost more than a knock-off carb.
Before tearing down carb, you could try Seafoam fuel treatment... probably less the 50:50 chance it will clear.
Posted on Mar 07, 2019
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Posted on Jan 02, 2017
This is a common problem. The needle and seat are prone to being held open from debris, old fuel (these days it only takes a month for fuel to start to go bad) and poor mower design. The weight of the fuel from the tank can be enough to overpower the float system with just the slightest "gumming" of the needle seat. Also, if it's equipped with an electrically powered valve on the bottom of the float bowl, this unit can outright fail, get gummed up a bit, or the electrical system have a problem and power is getting to this unit while switched off, leaving it open thus passing fuel. Most likely, replacing the needle and seat, giving the carb a good cleaning will solve your problem, however if there is damage to the seat from age or debris, just install a 2 dollar in line shut off valve available at most retailers. Then just turn the fuel on and off manually. Cheap fix. 2. Drain the oil from the engine, refill with new oil and just a oz. of atf (automatic trans fluid). Crank the engine with plug wire disconnected for 30 sec or so, then connect the plug wire. Start the engine, but only let it run near idle for a minute or so. Drain again, letting the crankcase "air out" with all plugs\dipstick removed. Remaining fuel will evaporate. Refill and your off and cutting......The ATF is a detergent of a type and will help to collect the fuel from the surfaces inside the engine. It's important to note the fuel will have washed any lubrication properties from the oil, and damage to the journals and other surfaces can happen if the engine is run too long. Usually following the above procedure will limit damage and the engine should be good for many more seasons. Good luck! Papa
Posted on Nov 15, 2008
I don't know if its any help but I've fixed my Honda with similar problem. It turns out I reassembled the rich carbys air cut off valve incorrectly. Have you checked yours? I'm wondering if the cut off valves somehow affect the other parts of the carbys. Mine is running sweet now.
Posted on Apr 24, 2009
SOURCE: mower surging
let it surge, it will usually get better as it warms up. These 6.5 Hp engines are fine except they have an cheap badly designed carburator. Nothing can be done about this problem. They all surge eventually.
Posted on Jun 16, 2009
may be dirt in the tank, or the feed pipe is deteriorated, clean the carb & float needle again and renew feed pipe and fit an in-line filter, ( will only cost a few pounds) it you still have the same problem then it's pretty sure to be the float needle & seat
Posted on May 27, 2010
Testimonial: "Thank you jim this has cured the problem."
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