yamaha 1kva <span class="highlight">generator</span>

What you could try is empty out tank on to a fine white cloth to see what's in the tank , if it leaves crud or dark stain .
I had this problem ,all the cleaning didn't fix it so replaced tank .

Mezza, have you cleaned the jets in the carby? taken them out and cleaned them?It sounds like there is a partial blockage, probably in the main jet, use fine fuse wire to clean it out, while the carby is off, flush the tank with clean fuel, it doesn't take much crud in the jets to make these small engines hunt.Good luck, Keith

One of the biggest problems with infrequently used outdoor equipment is stale fuel. It will gum everything up quick smart.
Modern fuel goes off much faster than in the past so this is becoming a common cause of problems in small engines.

I started using a product called STABIL about 10 years ago & I have never had an engine fail to start since. It will extend the life of the fuel for up to 2 years but has to be added at the time of fuel purchase. It will not fix fuel that is already gone off. I bought my last bottle at Bursons auto but I believe a similar product is available at marine engine suppliers. It can be used in all 4 & 2 stroke engines.

Wont fix your immediate problem but I bet it stops it happening again.

Cheers
Stu.

Mezza,
two other things that will cause the problem are air leak through a carby gasket and a stretched governor spring.

Hope you find it.

I have cleaned the jets carefully and intend to soak carby in some sort of cleaner as the next step. will also try Stu's suggestion for this fuel additive.

Hello Mezza,Ihave the same generator,about 8years old, had a hunting problem when it wae new fixed under warranty, it does not get used for long perids, always drain all fuel out carby included,it always seems to surge when first used after long periods, my fix is to put it under nearly maxium load for about half an hour, this usually fixes it. Friar

Hello mezza Iff you had it from new it should have had a carby upgrade and also a ecu upgrade depending on the serial no. This was a real issue with the ef1000is genys and even now they are not totally stable. I sorted mine by changing jets and just recently the state svc manager said they have increased the throttle return spring pressure under the electronic governer by giving an extra turn on the spring and that is also settling them down. I am a yamaha dealer and some of these have just about drove me to drink. In saying that just being a yammy dealer at the moment will turn you in to an alcoholic. my ef 1000is has done over 2000 hours. cheers mm

Is it a EF 1000 or the latest model sine wave S ?
If the older one like mine I fixed the problem.
I bought it from ebay hardly used and it surged like mad. The older ones do not have an idle circuit and the governor controls the speed.
I did a couple of things.
First check that the hertz is correct at 50. Mine was at 60.
Second I emptied the tank and added fresh unleaded not E10
Third I cleaned out the carby . In mine the emulsion tube seemed to be partly blocked.
After all this it still surged, so I upped the off load speed a little on the governor and now it is OK.
I also always run some additional load like a 100- 150W light bulb if I am running a variable load.
Finally I added POR15 Fuel Stabilizer to the fuel.
I also try to run it for 15 minutes each month or so to use up any fuel sitting in the carby.
BTW there is a yamaha generator Forum in teh US which is helpful.
Regards Philip A

What exact model do you have ? As for my EF1000iS - I start it up every month and run it for 10 - 15 minutes - it gets little real use on trips - just there as an emergency power supply in case of poor solar input - this regular running avoids stale fuels and the associated troubles. Only time I had an issue was with a vapour lock in very hot weather - cooled it down with damp cloths and then ran it with the back cover off. Been good to date.

hi mezza, i will do a s/n search in the next couple of days and get back to you. From memory all 7vv models had a carby change, 7vw models already had the other carby on them. The other thing to watch for is iff you run it just sitting on the ground in dusty areas it will suck up the dirt and put a coating of dust across the ecu and they will do funny things then. Have had to clean out a few of these. Always sit them on a bag or a old peice of carpet or something. cheers mm.

hi mezza, i have some info for you, can you send me a private message with your email on this site and i will email you the service bulletins with the info you require on the carby. the 7vv no you gave is a part no for the sticker. the serial no will start with 7vv but that is explained in the bulletins. cheers mark

hi mezza, apparently you have to be a member to send mms. here is my shop email, it has pretty good anti spam things. mec@lm.net.au send me a email and i will reply with the service bulletin attachments. in the subject line put yamaha and it will get through to me. cheers mm

It may be your fuel can that you fill the genny from. It could have crud in it. Regards G.T.