Runs for about 1/2 hour great but then starts sputtering and loses rpm. Does not shut off just keeps sputtering and jerking. I have pulled the carb, cleaned it, pulled the tank, cleaned it, removed the tank filter pick up tube and installed inline filter-still no change. Oil is changed and full, plug is new (old one was black-burning rich??). Not sure what else to do but haul it to a service center. Seams to start this while under a load but will continue the sputtering when load is removed. I use to think there was water in the fuel so I would let it run and it seemed to work its way out and would run all night-lately it just won't clear out. Can shut it down for awhile and start it up and it runs fine for awhile but then starts sputtering again
Any help would be appreciated. Disassembled carb, cleaned all jets etc and blew out with compressed air. Now wondering if its the carb causing the problem.
Rule #1 is to always make the easy shots first.
Since your sparkplug is black (over rich):
--Completely drain, carefully blow out everything with shop air and refill with new fuel.
--Be sure the paper air filter and it's outer foam wrap is clean.
--Be sure the spark arrester screen in the exhaust outlet is not carbon clogged.
--Check the carb float level*
--Lastly, check/adjust the valve clearances.
*High time engines normally wear a ridge into the float needle's rubber cone shaped end. Inspect the rubber cone on your genny's float needle. That vibrational wear eventually creates a higher (richer overall) carburetor float level. A quick check can be performed as slow moving fingers elevate the carb float while the same sensitive fingers tactilely determine when the needle's spring pin JUST touches and the play is zero. The hard way is to remove the carb and floatbowl, orienting it so the float "hangs" from the float pivot shaft. Then slowly re-orient the carb so the float just stops moving when the needle seat touches it's seat. Tilting it further will compress the needle's integral spring pin, so don't use that as the float level indicator. The plastic floats are not level adjustable, so replacement of the needle and possibly the float too may be required.
Hi guys,I'm a retired 30 year diesel mechanic!
I'm sad to say I have had the same sputtering problem for a month. I found the blue wire to the left side above the starter along with other wires.I gently pulled them all to the door opening far enough to isolate the blue wire.I gently pulled on it and it came unplugged at a bullet connector above the starter.My generator starts perfectly now.I'm trying to figure out if the sensor is located behind the flywheel? It is not in a obvious location. Or I could be blind in my old age.I ordered a new sensor online for $66.00 including shipping. Now should I go to the trouble to replace it? HELP
Had the same exact problem. I removed all the panels and gas tank to trace out the wiring. Foud the blue wire bullet connector on top of tank in a bundle. Pulled the connectors apart coming from the indicator light and on top of tank going to oil level sensor. Reconnected the wires and it has NOT missed a beat since. I think buying the sensor was a waste of money. Try and connect the wire and the other end of the blue wire on top of the tank. I have asked where the sensor is located but NO ONE has answered my question. In my opinion it is nothing more than a faulty connection. I have determined that the sensor is behind the flywheel. Way too much of a pain in the ass for me to disassemble. I would rather go the old fashion route and check the oil level on a regular basis. But that's just me. Try pulling the few connectors apart and reconnect them. I'm pretty sure it will work and y'all will still have the sensor in line.
I will rip mine apart and see if this is my problem. It just started doing this and only runs rough after it has been running for a while. Hope this helps me as Yamaha has not been able to find the problem
Yes, that worked on mine, it had been driving me crazy for a year, you dont have to take anything apart just remove the access door where you can see the starter and there is the wiring harness just above it, find the blue wire and pull down on it and it will come unplugged.
Same issue here, not sure what blue wire you guys are mentioning, i had my generator serviced and valves adjusted thinking it would fix this issue. took it home ran it with no load for maybe 1-2hrs. started it again a few days later and it ran maybe 3 minutes and the sputtering and knocking started now it just wont start normal. It begins with the sputtering from the get go.
ondahook, The symptoms you describe where it runs OK basically until the engine gets hot suggests an ignition coil problem that causes a weak/intermittent spark when it gets hot. The damage likely occurred to the electronic trigger circuitry by overheating the engine as would happen by running near/at the rated load in the sun on a hot day for a long period -or- if windblown paper litter of significant size got suctioned against the air intake while running.
Wrenchman, The oil level sensors are almost always inside the crankcase, submerged in oil, so the crankcase will have to be split to replace the sensor. The biggest clue is that the blue wire eventually connects to or is the wire color that goes thru the crankcase wall.
There seems to be a short lifespan of the Yamaha oil level sensor. This part, because of where it is installed inside the engine, should last a lifetime!
im done with mine, not sure what it could be but im going to get rid of it on CL, local Yamaha dealer swears they load tested it and works fine, but as soon as i get it home and start it up, the issue reoccurs again. Yamaha customer service told me might be my carb. Thats another 200-300 dumped if i do that.
Wow hate to hear that you were having the problem but hate even worse to hear you solution is to dump it on some unsuspecting CL buyer. I just bought one off of CL and is doing the same, maybe I bought yours. If it was not yours I hope you at least let the guy buying it know what he was buying. The guy I bought this one from certainly didn't. Oh well I guess some people just aren't real honest.
We have had our Yamaha 3000iSEB since 2007 and starting around 2011, we had sputtering whenever it got hot. We live in MS and use it tailgating from Sept to Nov. It would run fine at night but when the heat of the day kicked in, it would start to sputter. We had spark plugs replaced, carb cleaned multiple times and eventually replaced. We struggled with it for several years. Had it stress tested and everything and I finally stumbled across an online forum like this one that suggested that the heat did in fact have something to do with it and that the ignition coil may be the likely culprit. After my husband took it back to yet another shop and mentioned that, they agreed it was probably the ignition coil. We had it replaced in Sept 2013 and it's run beautifully through 2 football seasons - until this past weekend when it began sputtering again. Choked and sputtered in the heat of the day but came back after the game was over at 7PM and it purred like a kitten till we packed up and left the next morning at 10.
I found our old ignition coil receipt and the Yamaha part number is 7CF-H4640-00-00. I located a replacement coil on Amazon and a couple of other sites for $110 plus shipping. We're gonna replace ours ourselves and see if that fixes us again for another couple of years...
Good luck to all of you and I hope this helps someone.
I had the exact same problem. Firstly, thank you to the person first suggesting the blue wire/low oil shut off sensor problem. Mine would start sputtering after it got hot running for over 30 minutes in 100 plus degree weather. After many carburetor cleanings and other fuel system checks, I disconnected the blue wire at the bullet connection. It ran for 90 minutes! So while running, I plugged the blue wire back together at the connection and it immediately started sputtering. I then disconnected it again and it smoothed right out. I did this a couple of times which confirms that a faulty oil level sensor will malfunction when hot, causing the engine to sputter really badly. I thought if the sensor was faulty, that at least the oil warning light would come on, but it didn't. So unless someone posts a how-to on replacing the sensor (or if it takes completely removing the engine and splitting the crankcase), I'll just leave it disconnected and check the oil more often, although I never had to add a drop after many hours of use between oil changes. Good luck everybody!