Yamaha 1KVA Carby issue

Submitted: Sunday, Nov 01, 2015 at 18:07
ThreadID: 130759 Views:2396 Replies:5 FollowUps:7
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Hi All

Trying to help a mate out with his gennie. He didn't run it for a while so it blocked up. Have blown out jets (took main one out). I can get it running but it won't keep going unless choke is partially on. Starving for fuel I believe. Spark is good with new plug.
Which is the idle screw, the one with black plastic cap on it?
Ideas anyone......


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Reply By: Mudripper - Sunday, Nov 01, 2015 at 20:56

Sunday, Nov 01, 2015 at 20:56
Sounds like a sticking needle valve, but then if you say you blew out the jets perhaps that isn't the case.

My generator sometimes has the same problem (starving for fuel, have to run it on half choke) and it always turns out to be the needle valve.

Good luck.
AnswerID: 592242

Reply By: Member - Alastair D (NSW) - Sunday, Nov 01, 2015 at 22:09

Sunday, Nov 01, 2015 at 22:09
Try rinsing the whole assembly in a solvent like paint thinners. When old fuel is left it can build up a varnish like deposit that does not blow out.
Good luck.
AnswerID: 592245

Reply By: bellony - Monday, Nov 02, 2015 at 01:30

Monday, Nov 02, 2015 at 01:30
My Parents have the same genny that had identical issues. It turned out that there is a tiny tiny tiny bleed hole in one of the brass plugs/jets that gets blocked. It is so small that I had stripped and cleaned the carby 3 times before I even spotted it. After days of soaking in carby cleaner it eventually opened up with air pressure and the engine ran like new again. It is so small you wont have anything to push through it, and the guy recommended buying a new one. I found this info from a great website that had 1 contributor that knew everything about the 1KVA. Unfortunately I cant find any record in my favourites to pass on (was a few years ago).
AnswerID: 592252

Follow Up By: sweetwill - Monday, Nov 02, 2015 at 09:25

Monday, Nov 02, 2015 at 09:25
I had a while back never mist a beat, until the day I sold it, u got it would't start but the bloke who bought it was a small machine mech, all he did was clean out the filter and away it went.
FollowupID: 860379

Reply By: LandCoaster - Tuesday, Nov 03, 2015 at 01:07

Tuesday, Nov 03, 2015 at 01:07
Hi Lyndon, I am a bit of an expert on these jennys, if you follow this guide you should get it going....

New Oil. I use Penrite 30grade, doesn't smoke
New Plug, Critical!, Usually needs one every 4-6 tank fills. Sometimes you'll get a 'freak' plug which lasts ages.
Clean Filter
Standard Unleaded Fuel, Critical! If it's had any other than 91 rinse the tank and lines.

Dry out carby. Remove side cover, loosen float-bowl screw, remove fuel line from tank. Face carby into sun for quite a few hours
Blow out carby, gently, a few psi does it.

Leave the fuel bowl screw undone, zip the rest up, fill with fuel, wait till fuel drips from carby bowl, nip up screw
Choke on, gentle pulls on starter, should start.

If it still requires choke after this to run I lay 10-1 odds the exhaust valve port is carboned up, possibly the valve stem. Easy fix.
Remove the Blue Yamaha casing. To allow access to the rear exhaust manifold mount nut and rather than pulling the whole soundprooing shroud off, drill a hole into the shroud above the rear exhaust manifold bracket.
Remove Muffler.
Cleanout exhaust port.
Clean carbon of valve stem
Blow out cylinder with air
While the muffler is off, fire it to burn the carbon build up out of it.
While the covers is off, put a small fuel filter on the fuel line and a catch-can on the egr line.

Zip it all up, shall go beautifully

I've had mine for 7 years, it's done huge huge hours in the most adverse, horrendeous conditions and given brilliant service.
Definetly it like a new plug every 4-5 tanks of fuel. Service-Centre fuel only too

AnswerID: 592287

Follow Up By: Roachie Silverado - Tuesday, Nov 03, 2015 at 06:35

Tuesday, Nov 03, 2015 at 06:35
Thanks for the write-up mate!!

Coincidentally to the OP, I decided to check my Yammie 1KVa on the weekend too. It had been sitting in the boot of my camper trailer for many months with about 1/2 tank of fuel.

I decided to run it dry (took about 8 hours on non-eco setting) and was running a bit rough. If I switched it to eco setting it would surge badly.

I looked on Youtube and found a yanky bloke had a similar problem with his 2.4KVa model and solved it by spraying a carby cleaner into the carby. There were 4 different "chambers" (?) he tried and the first 3 made no difference, but when he squirted the stuff into the 4th one, it settled down to a regular pulse almost straight away.

I think I will try that option first. I did pull the plug out yesterday arvo and it looked a bit dirty/black, but otherwise looked okay, but on your advice I will buy a new one. Probably due for an oil change too.

Thanks again....I have book-marked this page for future reference!!

FollowupID: 860423

Follow Up By: LandCoaster - Tuesday, Nov 03, 2015 at 13:27

Tuesday, Nov 03, 2015 at 13:27
I can't remember the amount of times i un-nessarily stripped then cleaned down the carby, also cleaning the sparkplug, only to get a ever worsening hunt in eco-mode. Stripping the carby was to no avail. A drain, dry, fresh plug an' oil was all it really needed..

The design of the machines is pretty cool, the block/head splits diagionally, they are not symetric.
It was my fault carbon built up by running it only in eco-mode. The muffler filled up too. I split the crank to clean out the carbon that had packed and filled the 20mmx30mm irregular exhaust port/manifold (expansion chamber?) and valve stem. I fired the muffler
It ran like new with a new plug and single 30 grade oil, it ran whisper quiet, very very steady.
After the strip down i stepped up my prevenative maintence running it full-on for short whiles and swaping in a new plug and oil every 3-4 tanks.
Before I put a fuel filter and catch-can on it, occasionally the carby would need a sun-dry and blow if I had left it sitting, put containanated or wrong or old fuel or too much addative in it.

Mine has now done over, an astounding, 80000 Hours. I was full-time on-road for three+ yeasrs.. The first decarbon was at only 1200hours, that was my fault. The second decarbon was done at 50000Hrs using the method in previous post.
Im going to polish the ports and manifold the next decarbon to see how long i can get away running it in eco-mode...

Way way back and unlikekly to affect now and urban-hub-bub had it that the first batch if is's to Australia had packing gel inserted into thier fuel lines as an shipping requirement. Un-usually this small genny required pre-delivery at the distrubuters. Somtimes this wasn't done properly and people had hunting problems,.. That was wayyyy back, almost ten years ago. The dealership also told me to keep the oil topped right up, it helps in the sound-proofing.

Have a good run with yours, they are a good machine
FollowupID: 860453

Follow Up By: Phil 23 - Sunday, Nov 08, 2015 at 13:59

Sunday, Nov 08, 2015 at 13:59
New plug every 4 or 6 tanks for fuel?

I'd be spitting chips if I had to change a plug that frequently on My Honda.
EU10i, 15 years old, conservatively done 5,000 hours. Could be double that.

Always run on Premium 95 where possible & noticeably smoother than on Regular unleaded.
Think it's only on the 4th Plug in it's entire life.

Having to change a plug every 3 or 4 tanks would tell me something's seriously wrong.

Only maintenance rule I've followed is I've always carried two 10 litre fuel drums for it, and when each one emptied, I changes the oil, about 30 to 50 hours, depending on the load.
Always used Honda's branded oil, whatever it is, but felt it met all the requirements as well as being straight 30 weight.
240cc's of oil is not a lot, and it's probably the most stressed aspec of the engine.

Before I sold it I installed an hour meter & racked up 350 odd ours on an 18 month period, (been relying a lot more on solar in the past 3 or 4 years).

Sold it 6 months back, to a motor mechanic, he baulked at the age, but on inspection & seeing it running was happy to part with $550 for a 15 year old genny.

50,000 & 80,000 hours?
Is there a typo in there?

That's 5.7 & 9.1 years of running 24/7 without a break; that's a hell of a duty cycle for a 7 year old genny.


FollowupID: 860653

Follow Up By: LandCoaster - Thursday, Nov 12, 2015 at 09:36

Thursday, Nov 12, 2015 at 09:36
HI Phil, regular spark plug changes is a small price to pay for the yamaha, after all, it runs much quieter and longer than the Honda, ha ha ha. That's probably also reflected in its requirement for 91.
My manual does say to change the spark plug every 20 hours, but i usually stretch it to 30-40 hours. It usually doenst need changing, just a clean.

What does the Honda manual say about spark-plug replacement? Regular plug changes and small engines seem to go hand in hand.

My total hours on this genny are, 12x6x52x3 + 12x3x53x2.5, roughly 16000Hrs.
FollowupID: 860806

Follow Up By: Phil 23 - Saturday, Nov 14, 2015 at 09:07

Saturday, Nov 14, 2015 at 09:07
Honda's manual indicates an oil change at 100 hours spark plug at 300 hours.

I've always changed oil at around 25 hours, or as mentioned after 10 litres of juice.
Think I've only changed the plug 4 times in it's life.

Oil definitely shows a lot of discoloration at 20-30 hours, & hence must contain contaminates.

Maybe the more frequent oil changes have helped me with long plug life.

Can't quite guess it's exact hours, but we did burn heaps of fuel before we had solar & other efficient thing.

Newer Hondas than mine would show hours on start-up by flashing on of their indicators.

I find also the price difference in running Regular & Premium, is less significant as I do get longer runtime on 95 fuel. 5000 is totally feasible, 10,000 not out of the question.
Anything around 5,000 is a pretty good expectancy for a stationary engine before service.

Did seriously consider a Yammy when I upgraded to 2kV, but after much research & reading came to the conclusion the simplest answer was to stick with the devil I know.

Can't really see a clear cut winner in the Honda Vs Yammy race.

FollowupID: 860880

Follow Up By: LandCoaster - Monday, Nov 16, 2015 at 13:28

Monday, Nov 16, 2015 at 13:28
The Honda prolly wins on sales. They are both technically very different machines.
I do like the EU20 but it won't start the cheap air ill prolly end up with and ill go the newer designed EF2400 instead
Yamaha intervals on the EF1is's are Oil every 20hrs and plug every 50hrs, clean or replace. A while back I bought 6 plugs, swapping in a clean and/or new one when the idle become irregular. It also saves the mess cleaning them while camping. I've chucked 3 so far, prolly got 50hrs av before the idle got messy. Sometimes i get a plug that lasts for ages. Ages is a fullrun week, lol.

Last year I flew across the other side of the country, without my yammy, to bring a 4x4 bus back to brisbane. I bought one of the chinese Honda knock-offs. It would barely run my worklight, lappy, toothbrush and phone chargers. In comparison, the yammy lets me add a fridge and 32' screen to that load. When the yammy is loaded up it has this very cool little bark when I use the vertical scrollbar in firefox, but then again, the panel is driven by a good graphics card.

One thing i've wondered about the honda's, do they automatically increase revs as load applys? Do they automatically switch out of eco mode? When an EF overloads dramatically it revs right up then switch's off, Honda too?.

as you say, definitely regular oil changes is critical on these little engines...
FollowupID: 860953

Reply By: Member - lyndon NT - Sunday, Nov 08, 2015 at 12:37

Sunday, Nov 08, 2015 at 12:37
Thanks for all the replies folks. We had another crack at it yesterday. Soaked in carby cleaner and blew out jets again. Think it might now be fixed. One really odd thing is I can't find any idle screw? Seems this is achieved by moving the throttle cable in the lock screw. Or are we just partly putting the choke on by doing this which will= it running rich and carbonising up

Thoughts anyone?


Now is the only time you own
Decide now what you will,
Place faith not in tomorrow
For the clock may then be still

My Profile  My Position  Send Message

AnswerID: 592467

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