Honda EU10i generator repair hints

February 16th, 2008

On Tuesday night, at around 10 at night, the generator, which had been running happily for three hours or so, suddenly stopped dead. I went out to investigate, and found that it still had fuel in the tank and wouldn’t restart. I cursed it mildly and packed it away for the night. It was dripping wet from the thick fog we were having, and it occurred to me that the last time it had died it had done so after Cambridge had experienced torrential rain.

Some preliminary investigations revealed that the oil warning light came on as you pulled the starter, which had also happened the first time. As the guys at Elliotts (who’d repaired it last time) had said there was water in the fuel that time, I thought I’d investigate this first. In the back of the owners’ manual it explains how to drain the carburettor, which seemed like a good thing to try. Water is heavier than petrol, so it sinks to the bottom of the tank, where it goes down the fuel line and into the carburettor. To drain the carb, open the side maintenance panel (the one surrounding choke lever) and pull out the three lengths of clear plastic tubing that are tucked into the casing – they’re not attached to anything at the bottom. Put them into a container of some sort (I used a large jam jar) that you can use to catch the water/petrol when it drains. Make sure that the engine switch (which is also a fuel valve) is turned ON and then undo the screw on the bottom of the carburettor by a few turns, and the fuel should start to flow. About 200ml of fuel should drain out, and you should be able to tell if what you have is water or petrol.
Mine was definitely petrol and not water!
If you disconnect the HT lead from the spark plug and pull the starting handle, you will pump fresh fuel from the tank through into the carb – you can empty the whole tank this way if you have enough patience.

drain screw
Position of the carburettor drain screw

Of course, this didn’t solve my problem, which left me thinking that the problem was electrical – some damp mucking with the electrics and preventing the engine from firing. So, last night, seeing as it was clear and breezy, I left the cover off the genny to help it dry out.
This morning, when pulled over, it spluttered briefly into life and then died. Further fiddling made it start about one time in twenty. At this point, encouraged that the thing wasn’t entirely dead, and with assistance from my landlord Martin and his daughter Sabrina, I took the whole thing apart for further investigation.
This is slightly fiddly, but easy when you know how. Now that I do know how, I’m sharing that knowledge, as there seems virtually nothing on the internet about how to fix these generators, which gives an idea as to how reliable they are!

Anyway, first drain the fuel tank – this isn’t totally essential but is recommended on safety grounds. Next, remove the side maintenance cover and unscrew the grey plastic end covers (one around the sockets, one around the exhaust) – they both undo with four screws each and then pull off. To take the rest of the casing off, first peel back the rubber surround around the fuel cap on the side nearest the sockets – you’ll find a small brass circlip which you need to prize off. This is a bit of a fiddle, and even more so to get back on again unless you have circlip pliers.

The circlip under the fuel filler surround

Now undo the screws on either side of the socket panel – there’s one on each side. They’re not captive, so remove them completely from the cover rather than dropping them on the ground when you tip the unit on its side! Roll the unit onto its side, with the starting handle downwards, and undo the screws in the handle and the base. You’ll need a Philips No 3 screwdriver (PH3) and if your unit is like mine, the screws will be very tight indeed. You should now be able to lift off the plastic cover and get at the insides in an ordered fashion. Alternatively (as I did), split the cover in half whilst the machine is upright, and watch everything spill all over the floor!

generator in bits
Anatomy of an EU10i – from back: engine/alternator block, fuel tank, inverter, socket panel

I was looking for the ignition system wiring, which is buried at the bottom of the casing underneath the engine and the inverter unit. This turns out to be a bit below Honda’s usual high standards – the ignition wiring has lots of connectors (some multipole and some bullet crimps) and none of them are very well waterproofed. What eventually solved my problem was getting at the engine switch, which is actually a small black microswitch just below the edge of the maintenance panel. It’s pressed in by the white plastic rod that’s turned by the engine switch knob itself. It’s a proper pain to get at, as you have to unscrew it from the cover from the inside, which involves moving everything else out of the way. Anyway, having unscrewed it, I was able to trace its cable back to a two-pole connector covered in muck and sludge, which I disconnected. Having done this and cleaned the connector, I pulled the starter carefully, and the engine sprang into life. Of course, it wouldn’t stop, as I’d disconnected the ignition switch (oddly, the switch closes to stop the engine) and so we had to stop it by pulling the HT lead off the spark plug.
I decided at this point to clean the water/oil/petrol/WD40/grime out of the casing and electrics, and to waterproof the ignition system connectors with self-amalgamating tape. Thanks to Helen for buying me some whilst she was in Cambridge!

The engine microswitch

Reassembling the generator was a bit fiddly, too. Firstly, reassemble the engine mountings – the rubber disks and metal shafts – there are two in the bottom and one in the handle.

half-assembled generator
The generator with one side removed. Note the three round engine mountings

The inverter unit (the slim aluminium unit) and the fuel tank have to fit together quite tightly, and there’s a rubber spacer that holds them in the right position:

inverter and fuel tank
The inverter (top) and fuel tank (bottom) with the rubber spacer between them
Reassembling the case is fairly easy as long as you have the inverter and fuel tank located correctly in their mountings. You may need a second pair of hands (thanks Sabrina!) to hold the casing together whilst you get the circlip back on.

Anyway, I now have a working generator, and am going to take more detailed steps to stop it getting wet in future – but I hope my experience will help anyone else who suffers similar problems.

48 Responses to “Honda EU10i generator repair hints”

  1. Cy Says:

    That looks like some hideous “no consumer serviceable parts” device. – don’t suppose you’re handy with cylinder head gaskets too?

  2. Ray Oakhill Says:

    Well done for describing how to strip down this generator – have not found it anywhere else on the net. I actually found the casing screws impossible to undo, not just difficult! But I did manage to strip the carb through the access panel. My problem was that it was ‘hunting’, possibly through water in the fuel (according to the Honda engineer I phoned). I did not find any water at all and the engine continued to hunt for some while after, but it gradually returned to normal with continued use and is fine now. Might see you one day, if I’m in your neck of the woods. have fun on that boat.
    Ray Oakhill. n/b Stronghold. River Wey.

  3. Alan Murray Says:

    That little Honda EU10i is an engineering masterpiece and although expensive when I bought it 5 years ago – every time I use it, I’m glad I had the sense to buy it. Very few automatic battery chargers will work properly (Or at All) on anything but a Honda inverter or its Yamaha equivalent. Most of the standard engine driven alternators have a regulator that causes the AC output to have a zero crossing glitch that upsets the AC timing and measurment program in the microprocessor. The inverter generators dont have this problem. Most PC standby PSU’s have built in microprocessor controled battery chargers to recharge the internal battery after a power failure. Although a standard desktop PC power supply unit will quite happily run off the glitchy output from a standard generator, a desktop PC and line innteractive standby PSU wont. The PSU battery charger “Sees” the erratic zero crossing spike as a timimg error and so cycles the inverter on and off. If allowed to continue, this on/off cycling will destroy the PSU and the PC attached to it. My Honda EU10 runs on almost a daily basis. When the mains supply fails, the Line Interactive PSU’s (There are two of them) take over the load to keep the PC’s, Ethernet and ADSL Modems running while I start the Honda and take the PSU power plug from the wall socket and plug it into the Generator socket. With practice this takes less than two minutes. The Honda EU10i with the Ecothrottle Switch ON will run almost all day on a tank full of Unleaded gas.
    To RayOakhill – Unscrewing the frozen Philips or PosiDrive casing screws is almost impossible unless you start with a screwdriver with the right shape and correctly fitting tip. Even then, you are likely to unscrew them without damaging the heads or the screwdriver. After damaging a couple of motorcycle cover plates a very experienced Aircraft fitter told me to try coating the screwdriver tips with a thin film of fine grade valve grinding paste.
    Wheb the job is done BE VERY CAREFUL TO WIPE ALL SURFACES CLEAN. Any residual traces of Carburundun contaminating bearing surfaces will destroy the engine.

  4. Michael P-J Says:

    Alan: thanks for the hints. I’m certainly very impressed with my EU10i, and now that I have the Victron inverter/charger unit fitted to the boat, I’m able to take full advantage of its performance. In particular, I had been charging the boat’s domestic battery using the 12v output from the EU10i, which only works properly with the genny at full throttle (Eco Off). Since installing the Victron unit I can now switch to Eco mode and my fuel bill has dropped dramatically!

  5. Alan Murray Says:

    Hi Michael: The battery charging output of most generators is far below the rated output of the machine. Most ordinary manually controlled chargers will also waste a lot of power because a simple rectifier output charger has a very poor power factor (Tipycally 0.5) so a 1000 watt generator will at most deliver 500 watts of charging energy – the rest is wasted as heat. The solution to this is a “Power Factor Corrected” charger. They are available but cost far more than a standard automatic charger and since very few customers are aware of the advantage of the power factor correction no one is prepared to pay the extra cost. Its only when you see the dramatic drop in fuel consumption that the value of a power factor corrected charging system apparent.

  6. Michael P-J Says:

    Alan: Ah, that’s interesting! I’d not particularly looked at battery charging technology before (despite being an electronic engineer) so it’s useful to hear your comments.

  7. Offmains Says:

    Nice to see that someone has taken the time to show how to take the case off of the eu10i.
    What a wizard of technology, a credit to Honda.
    I repair about 5 of these generators a week, most of the work is ring replacement which is quite a job, takes 4 hours from start to finish.
    The main problem with these little generators is that they are seldom used to their full capacity, often just charging a battery, so it is no surprise to me that they get gummed up around the piston and valves.
    Lack of proper maintenance is another problem, it is all well and good to change the oil and spark plug but what about the valve clearances? Yep it is a big job that can take an hour and half but well worth the effort.
    Just a point to remember, The DC charge on the EU10i is for a quick charge and should never be used full time because it will boil a battery dry…..OK those of you that know your onions out there might be saying that once the battery reaches the charge voltage then it will
    float….Wrong, the output voltage DC on the EU10i is as high as 30volt!!
    So with that lot if you need parts or service/repair get in contact

  8. fras Says:

    What is the proper valve clearence on thses generators?

  9. Richard Says:

    Hi Fras, according to the owner’s manual for the US 120 volt version the valve clearances when cold should be:

    IN: 0.08mm +/- 0.02 mm
    EX: 0.11mm +/- 0.02 mm

    I doubt if the valve clearances are different for other countries, the engine is probably the same it’s just the electrical side that’s different. Hope this helps.

  10. Peter Noble Says:

    I’m rather surprised to hear such unconditional praise of the EU10i. Its a very clever piece of kit but to my mind they just don’t last long enough to be worth the money. I am a Honda generator technician and like the other contributor I see lots of these come in for new rings. Problem is that as there is no liner in the cylinder bore they wear the bore as much as they do the rings. Replacing the rings will stop them smoking for a while but the cylinder is worn too. Also the plastic cam cog wears and melts and that is why they sound all tappety. My opinion of the EU10i is that its a good idea poorly executed. Anyone would be much better off buying an EU20i which has a proper engine and in my experience seems to be quite bullet proof.

  11. dylan byers Says:

    hi iwas just wondering if you knew what the valve clearance settings were

  12. dylan byers Says:

    hi sorry bout askingt that but i didnt read the whole write up

  13. dylan byers Says:

    hi can we put bigger rings in after the bore wears to compensate for that wear

  14. dylan byers Says:

    hi iwas after a flywheel for a eu 10i generator and was wondering if u would know of any cheap second hand one around or wondering if you u could put new magnets on the in side of them any help would be very apreciated

  15. john li Says:

    i have a honda eu10i. it starts normally. output light is on, when i switch off the econoswitch, idle speed will not increase. there is no ac output and dc output. honda service center in our place is impossible. any help is highly appreciated. thanks.

  16. Michael P-J Says:

    john li: that sounds bad. From my basic reasoning, either the electronics have packed up, or the alternator isn’t generating any output and the control electronics aren’t powering up. I’d check all the connectors inside for loose connections, water, etc, but beyond that it needs to see a professional.

  17. Peter Sidler Says:

    My Honda EU10i which I bought second hand does too much voltage. 250 VAC instead of 230 VAC. is it possible to adjust that?

  18. Michael P-J Says:

    Peter: no, it isn’t – all the electronics are in a sealed package. However, here in the UK the mains supply is 230V to a tolerance of 10%. 250V is within tolerance, so, I think your generator is working correctly.

  19. Luis Arce Says:

    HI, I have a problem with my Honda EU10i. I have 12Volt but no lights and no AC voltage on the front panel. All this after I disassembled the motor because a mechanical failure (dust in the carburettor). Oil level is ok, and gasoline is clean, so after the self reparation the motor works good but I don’t have electricity. Do I forget something like grounded, or oil level sensor.
    I would appreciate your help.

  20. Michael P-J Says:

    Luis: so the engine runs but you have no AC output? I would first check the AC circuit breaker on the front panel, just in case, and after that dismantle the generator again and check all the connectors, especially those going to and from the inverter module (the silver-grey lump of electronics). Disconnect and reconnect all the connectors and make sure that they are clean and dry.

  21. Aggie Weston Says:

    I have a Hoda 10i which will only run on choke. I took it in for service and the verdict was that I need a new carburetta. Can anyone advise me if this is right as I do not want to spend 100 pound unnecessary. aggie

  22. Michael P-J Says:

    Aggie: I’m not much of a mechanic (I’m an electronic engineer by trade), but the explanation that’s been given to you makes sense to me. The carburettor mixes air and fuel to go into the engine – closing the choke makes the mixture “richer” to help the engine start when it’s cold. If the engine won’t run with the choke in the normal position, then there’s definitely something wrong with the carburettor. I doubt that your dealer is trying to rip you off. £100 sounds pretty reasonable to me.

  23. Aggie Weston Says:

    Michael, Thanks for putting my mind at rest The 100 pound is the cost of a replacement carburettor together with labour the total cost is 250 pounds so I might have to leave it for a bit. I have thought about converting it to LPG (but would I still need a new carburettor ?)or selling it has described on ebay. aggie

  24. mark Says:

    hi i have generator eu10i with a non uk facia its 220v it came with two small 3 pin plugs can i change the facia to a uk facia or if not how do i use these plugs will they run tyre warmers for a motorbike .thanks

  25. Michael P-J Says:

    mark: the simplest way will be to find a suitable plug to fit your sockets and buy or make an adaptor cable. CPC are a good source of electrical bits –

  26. Luis Says:

    I have a rare problem with my eu-10. The inverter module is partially operative. I look that the SpU(spark unit) is operative because the engine starts. In the other hand I have 240 volt from MW (main winding) and 6 volt AC from SW(Sub winding) at the IU(inverter unit) connectors(Is that ok?). I think the Sw voltage is for electronic control and the three faces or MW are the power to be rectified and converted in 240 sine AC volt. But I don’t have AC output, the leds are off and the servo is not operative.
    I checked the connectors and clean them several times with no results.
    The only voltage at output is 12DCvolt.
    I can’t believe the inverter module be defective because it was not overloaded and I was very careful with the operation. But, if I have to replace it, I would like to know where can I buy it directly. I am in Mendoza, Argentina.
    Thank you very much and congratulations for the information posted.

  27. Michael P-J Says:

    Luis: okay, that’s well outside the scope of my experience – sorry I can’t be more help. I think that you should go and see a Honda dealer, who may well be able to supply you with a replacement part you can fit yourself.

    Honda have several appointed dealers in Mendoza:



  28. Luis Says:

    Ohh Mike!. Veo que hablas español. Gracias por tu pronta respuesta. El equipo estuvo en el concesionario que me recomiendas e increíblemente la respuesta del técnico fue que no tenían el equipo mìnimo como para diagnosticar la falla. Esa es la razón por la cual estoy haciendo personalmente el seguimiento. Igualmente te agradezco el aporte. Has sido muy amable. :)

  29. Michael P-J Says:

    Luis: he apprendido mi español en Bariloche en 2007, pero no hablo mucho ahora!

    Espero que tu podes encontrar un solution. La empresa ingles “Offmains” ( estan los expertos – sugiero que hablas con ellos.

  30. Luis Says:

    jaja…tu español es muy buenoooo!!
    Bariloche es un hermoso lugar para empezar a conocer Argentina…hoy está cubierto de cenizas por una erupción de un volcán del lado chileno pero es algo a lo que los lugareños ya se están acostumbrando.
    Te mando un abrazo inmenso y muchas gracias por tu aporte.

  31. Andrew Reid Says:

    Have you any advice about fitting an exhaust extension to an EU 10i? I am an engineer and will weld fittings. Idea is to charge battery inside boat. Am grateful for help. Andy

  32. Michael P-J Says:


    Electronics is more my line, to be honest! I’ve seen a number of EU10 box covers and mods that have been done in order to have the machine stand outside in all weathers, though never one with a longer exhaust pipe. To be honest, I had mine on a long security cable attached to the boat and put it on the bank when it was running – no fumes indoors and no irritating vibration.

  33. Andrew Reid Says:

    Thank you Michael, tomorrow I shall take the silencer box into a plumbers store and match a tube to weld around the outlet pipe but with it’s O/D smaller than the plastic cover. Then to the hydraulic hose company for hose to push/ clamp over.
    The exhaust seems to run quite cool and I would like to keep the gen inside the boat. Andy

  34. carlos tabacchi Says:

    buen dia necesito un gia para ensanblar los engranajes del cigueñal y el arbol de leva y la pocicion de los taquetes

  35. Michael P-J Says:

    Carlos – Lo siento, no se… soy ingeniero electronico solo.

  36. carlos tabacchi Says:

    gracias Michael alguien puede decirme donde buscar

  37. noel Says:

    Could someone advise how to overhaul ther carb on the Honda EU 10i, i have a float and needle set comming in the post and need some advice

  38. peter Noble Says:

    Best advice I could give anyone with an EU10i is to mix a little two stroke oil with the petrol. A 400:1 mix ought to be enough. The EU10i lacks a cast iron cylinder liner combined with poor uppercylinder lubrication so a spot of two stroke really makes alk the difference. I have a customer who is a market trader who uses an EU10i every day. In normal circumstances this would result in rapid wear and oil consumption but due to his adding two stroke to his fuel his machine is 3 years old and still in reasonable mechanical order.

    As for the fellah thinking about welding an extension to the exhaust m,y advice woiuld be don’t do it. The UK military tried adapting the EU10i as a light weight field generator and they fitted in ruggedised case with exhaust ewxtensions etc. The result was much money spent and a lot of knackered generators appearing on ebay. The EU10i is a machine that runs on the edge and modifying it is really playing with fire. Best idea of all is forget the EU10 and get an EU20 or an EX650.

  39. Michael P-J Says:

    Pete: that’s useful insight, thanks. I never intended this page to be a self-help group for EU10 owners, but it seems to have turned out this way…

  40. Gary Says:

    Hi Noel

    There is a good exploded diagram of a honda carb here. The Eu10i is essentially the same aside from the stepper motor assembly which is fastened to the top of the carb with two philips machine screws

    Be careful if you remove it as there is a little spring (like a shorter version of a ball point pen spring) between the throttle arm and a little nylon cam which is pushed over the stepper motor spindle.

    The float bowl also has a drain screw not shown on the diagram.

    Unscrew the float bowl screw (11) and don’t lose it’s rubber O ring or the float bowl O ring

    Gently push the float pin out. The float valve (10) will remain attached to the float. Check for wear and debris + don’t lose the spring!

    The main jet (4) has a slotted head. Unscrew that and it will drop out. Tap the emulsion tube on a soft surface and the main nozzle (5) should also drop out.

    I would leave the pilot screw (idle mixture screw) in place as it has a tamper proof cap. Put the dismantled carb in an ultrasonic cleaner (twenty odd quid from Aldi) (- the stepper motor of course) with warm water and a bit of stardrops for half an hour. Don’t use carb cleaner as it is flammable and will also damage the plastic parts.

    If you don’t have any cleaning needles for the main jet and nozzle put them in the ultrasonic, rinse (in clean water) and then spray (or soak in) carb cleaner. Rinse the rest of the carb body thoroughly then blow dry with an air line, blowing through any jets (holes) in the carb body you can access. Finish of the main jet and nozzle with air as well as it is the main jet that usually gets clogged with fuel varnish.

    Reassemble in exactly the opposite order you have dismantled and make sure you don’t cross thread the main jet as it is only brass. O rings can also get damaged upon reassembly so make sure they are properly seated before tightening up the float bowl.

  41. Barbara Says:

    Thanks boys for all the helpful advice, for my Honda EU10i, used almost daily from 2008 till 2012. Have done all maintenance myself, wifh help from Honda technicians and owners manual, but am tired of smart talk from a Honda agency. Will try the repairs myself for current erratic behaviiour of ny trusty mate..
    Aging 72 yr old in remote rural Australia

  42. pete Says:

    hi my honda eu 1000 i is a 1999 model and i use it regularly ,here we are in 2013 its still running and starting with no smoke ,one of the best investments ive ever made,im now looking to purchase a honda eu 2000i, but at well over a grand new ,i will have to go secondhand,hopefully it will b e just as good as eu 1000,many thanks for all this very usefull info,as like many other owners i was unable to find how to dismantle my eu 1000,

  43. Paul Clements Says:

    Can any one tell me how to stop the carby from continually flooding This is with a brand new carby?

  44. Hojong Lin Says:

    Just cleaned up pilot jet of a Honda EU10i. How do I adjust the throttle screw now?

    Yup, I forgot to count how many turns it was set. Stupid.

    Anybody? Thanks in advance.

  45. Nils Isak Sara Says:

    Paul Clemet: You must clean the pilot jet.

  46. Ulf Says:

    I use a Honda EU10i since many years on my RV. It is supplying 230V to my Mastervolt MassCombi which again charges my 24V batteries or supplies direct 230V in the RV. Since a few weeks the EU10i seems to have trouble keeping the output voltage stable – dropping to about 200V which again stops the MassCombi to charge, dropping the laod on the generator which in turn results in a cyclical running of the engine with an interval of about 10 seconds. This means the generator produces full load for about 10 secs, then the voltage drops, stopping the charging and removing the load from the generator for a second or 2 and then the cycle begins anew. Any ideas where to start checking what is going on?

  47. Nigel Wright Says:

    Hi I have an EU10i that runs full throttle all the time and the eco switch will not drop to idle. It is generating power fine. The stepper motor is working because when I manually move the exo throttle to idle, as soon as it starts it moves to full throttle. Almost like the controller thinks it is under load when it’s not. Any advice would be great.

  48. admin_user_1 Says:

    Hi Nigel – I can’t help you very much, unfortunately – I’ve long since sold my EU10i. My suggestion, and this is just a hunch, is that the eco throttle operates with a feedback loop from the generator – either counting frequency or measuring load current – and if this input fails, it may “fail safe” by running the generator at full throttle. I would therefore look closely for broken wires or bad connections in the wiring harness.

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