Auto Choke Doesn't

[Prajna]

Greetings, O Font of Engineering Knowledge. I was recently given the magnificent beast you see in the image(s) below. It runs smoothly and produces a nice stable 400v (Mike having cleaned the commutator).

But. It just doesn't want to start without a squirt of break cleaner in the carb. It has what I imagine is an automatic choke with a fuel enrichment circuit that operates a needle at the bottom of the carb and what looks like a vacuum servo that seems to be connected via a complicated mechanism to the choke butterfly at the top of the carb. Carb looks like this:

The carb claims to be a Heonda, which I think is some kind of Chonda (Chinese Honda copy) but various internet search engines have failed to produce any worthwhile results and I figured that when the internet fails to give enlightenment then the only hope is to pray to the gods on this forum.

Can anyone tell me how it is supposed to work? There is a manual choke lever (the hook you can see top right) and it pushes and pulls but doesn't seem to close the choke butterfly. I tested the enrichment needle by connecting it to the 12v battery and it extended and then retracted when disconnected, so that seems to be working. There is a plastic cap on top of the butterfly axle with a hole for a pin to one side so that it operates as a crank. There is a pin in the choke lever mechanism that fits in the hole in the cap. Pulling the choke lever with the pin engaged does appear to try to close the choke butterfly but the mechanism locks up before the butterfly moves much. Never having seen such an arrangement before I am at somewhat of a loss as to how it is supposed to operate and why it doesn't. T'will be a great luxury to get this machine working because it is purported to give 5kW, which is double what my current gennys offer (although that 5kW might only apply when using the 3 phase outlet. Do I get the same from the 240v socket?)

 

[GRW]

I've not seen that extension on a carb either - but it not starting without a whiff of ether is more likely a product of the carb being gummed up with the varnish-like residue that evaporated unleaded fuel deposits.
If you get it started on Ether... dies it then continue to run, or stall out? If it runs - does the engine "hunt" and/or die if you close the manual choke?
All the above are symptoms if a gummed carb / emulsifying tube & galleries.
Stripping & cleaning the carb well (ultrasonic cleaner if you have one) and reassembling would be a good start. (Obviously make a note of the air screw turns out first).

 

[Prajna]

I've not seen that extension on a carb either - but it not starting without a whiff of ether is more likely a product of the carb being gummed up with the varnish-like residue that evaporated unleaded fuel deposits.
If you get it started on Ether... dies it then continue to run, or stall out? If it runs - does the engine "hunt" and/or die if you close the manual choke?
All the above are symptoms if a gummed carb / emulsifying tube & galleries.
Stripping & cleaning the carb well (ultrasonic cleaner if you have one) and reassembling would be a good start. (Obviously make a note of the air screw turns out first).

I didn't try the manual choke once the engine started but, with the air filter off, I can see that operating the manual choke only moves the butterfly a small amount, it certainly doesn't close it. As soon as the genny is started it runs smoothly (and surprisingly quietly) and doesn't hunt. I did disassemble the carb and gave it a good spray out with break cleaner (no carb cleaner to hand) and a blow out with the air compressor. As I say, it runs great it just doesn't start without a squirt, which is what led me to believe that the problem is with the choke. I didn't do a full disassembly of the carb. I don't have a parts cleaner but I can take needles out and do a more thorough job than I did.

 

[GRW]

Note also that being a generator the carb has a mechanical governor linkage & springs that control the throttle butterfly etc. Its possible it's been meddled with, but if it starts and governs speed (or tries to by the governor linkage opening and closing the butterfly as it tries to stabilise the revs with a gummed carb) then it's a positive sign that it might be connected properly

 

[GRW]

I didn't try the manual choke once the engine started but, with the air filter off, I can see that operating the manual choke only moves the butterfly a small amount, it certainly doesn't close it. As soon as the genny is started it runs smoothly (and surprisingly quietly) and doesn't hunt. I did disassemble the carb and gave it a good spray out with break cleaner (no carb cleaner to hand) and a blow out with the air compressor. As I say, it runs great it just doesn't start without a squirt, which is what led me to believe that the problem is with the choke. I didn't do a full disassembly of the carb. I don't have a parts cleaner but I can take needles out and do a more thorough job than I did.

I've seen a few gummed up small genny carbs. The issue is the carbs are small so the hidden galleries (that often supply fuel for no-load running) through the body, they block/restrict very easily.
Often, a genny will run only with part-choke off-load, but runs better once on the main jet under load if the carb is partially gummed.
A carb strip and blow through every body orifice with compressed air after cleaning. And remove and clean the emulsifying tube that the main jet sits below is a good start.

 

[EBME2]

Looks similar to below from picture

https://amzn.eu/d/hcz4toW

 

[GRW]

Looks similar to below from picture

https://amzn.eu/d/hcz4toW

At that money it's worth buying a complete carb

 

[Prajna]

Note also that being a generator the carb has a mechanical governor linkage & springs that control the throttle butterfly etc. Its possible it's been meddled with, but if it starts and governs speed (or tries to by the governor linkage opening and closing the butterfly as it tries to stabilise the revs with a gummed carb) then it's a positive sign that it might be connected properly

I runs very smoothly under no load and I also plugged in an angle grinder to test the 240v socket. The genny picked up speed smoothly to handle the load of the grinder, so I think the governor is working well. The volt meter shows a beautifully stable needle thanks to Mike's expert cleanup of the commutator. I have another (2.3kW) genny that I had written off because it was producing no output even after I fitted a new AVR and brushes. Measuring various resistances and voltages and sending them off to tech support at generatorguru returned a diagnosis that the armature needed replacing (i.e. beyond economical repair). Then, after Mike had problems with output on his genny he gave the commutator a good clean and that is now rock steady, so he went on to do the same for one of my other gennys with beneficial results. So we thought, might as well drag the US genny round and try the same. Bingo, that revived it, so now I have two 2ish kW gennys and, once I get this one starting properly, a 5kW with the bonus of 3 phase if I ever need it.

 

[Prajna]

Looks similar to below from picture

https://amzn.eu/d/hcz4toW

That does look very much like it. The problem seems to be with the choke mechanism that is external to the carb, so it would be pointless to replace what appears to be a working carb with a new one. It would be nice to know how the mechanism is supposed to be assembled (should have made photos/notes before disassembling it but there doesn't seem to be any other way to put it back together). What's the vacuum servo supposed to do? Is it part of the choke system - to reopen the choke once the engine starts? Is it part of the governor? It has the usual push rod and spring arrangement for governing. Is the manual choke supposed to operate when there is a fuel enrichment circuit or is it only needed when there is no fuel enrichment system? At least that link identifies some other Honda carbs I might be able to get actual information about. Thanks.

 

[chrismac]

I've not seen that extension on a carb either -

is the green extension a fuel shut off? or have I picked you up wrong, you know your stuff when it comes to gennys,
Edit just went a look.

https://www.amazon.com/Hetong-Carburetor-Solenoid-Accessory-Generator/dp/B09QSQ83SZ

 

[Prajna]

is the green extension a fuel shut off?

I gather it is a fuel enrichment control. They're used on some scooters, I believe. When there's no voltage on it the needle is retracted and extra fuel can flow into the carb and when the engine has started 12v is applied to what I imagine is a solenoid that extends the needle to seal off the enrichment port (or maybe vice versa - certainly the needle extends when hit with 12v).

 

[angellonewolf]

At that money it's worth buying a complete carb

I've used a few copy carbs China ones they either work fine or don't work at all

 

[GRW]

I gather it is a fuel enrichment control. They're used on some scooters, I believe. When there's no voltage on it the needle is retracted and extra fuel can flow into the carb and when the engine has started 12v is applied to what I imagine is a solenoid that extends the needle to seal off the enrichment port (or maybe vice versa - certainly the needle extends when hit with 12v).

An Automatic Choke. Sounds feasible. I know they could be fitted to some electric start Honda's to enable them to be started remotely (like Onan type petrol gensets in RV's have that feature)

is the green extension a fuel shut off? or have I picked you up wrong, you know your stuff when it comes to gennys,
Edit just went a look.

https://www.amazon.com/Hetong-Carburetor-Solenoid-Accessory-Generator/dp/B09QSQ83SZ

I'm not any authority at all on the Chinese stuff - they were not viable to repair where I usedto work, as their low initial price and total lack of data, resistance values etc made them too much hassle to take in.

The "Generator Guru" is the place I suggested those who contacted us with problem Chinese stuff tried for parts & help. He seemed to have a good handle on which AVR for what set (the most common weak point) and knew what wire colours were exciter etc - GG seemed to specialise in them.

Bigger industrial stuff was where I worked's main business. They'd take on small typical Honda, Kohler, Lombardini, Yanmar kit, as they invariably ran Euro-made alternators and had enough value to warrant labour costs to fix.

 

[Nomad]

What is the manual choke lever connected to ( some are to the butterfly, others are to an enrichment jet)?

The butterfly on my mower is for the load control not for staring - maybe similar for yours?
Can you hold the butterfly closed manually when you try to start it just to prove the butterfly is the choke..

Strip the carb and blow carb cleaner / brake cleaner though every jet and drilling in the carb body? I've stripped the carb on one of my long-standing projects 3 times so far - it runs better every time but still won't tick over when hot.

Run the genny up to temp a few times and hope the heat cycles clear whatever is blocked??

Edit: the electrical connection could be a fuel cut off solenoid, or could be an idle enrichment device that isn't working ( no power or blocked jet/drilling). Use a multimeter to test for power at the solenoid before & after startup?

 

[Prajna]

What is the manual choke lever connected to ( some are to the butterfly, others are to an enrichment jet)?

The butterfly on my mower is for the load control not for staring - maybe similar for yours?
Can you hold the butterfly closed manually when you try to start it just to prove the butterfly is the choke..

Strip the carb and blow carb cleaner / brake cleaner though every jet and drilling in the car body? I've stripped the carb on one of my long-standing projects 3 times so far - it runs better every time but still won't tick over when hot.

Run the genny up to temp a few times and hope the heat cycles clear whatever is blocked??

When the mechanism is removed the butterfly closes and opens easily. The (mechanical part of the) mechanism is a bent wire consisting of the hooked choke lever which actuates another bent wire 'box' or square, giving some movement or backlash to a pin (another piece of wire) that swivels and engages in a hole on the tab sticking out of the plastic cap on top of the butterfly axle. It's hard to describe but I can take the air filter off later and get a photo. But because of the radius of the swivel on the pin the mechanism locks before it can rotate the butterfly fully. It doesn't look like any of the wires are bent out of position or that I could adjust them to make it work.

 

[GRW]

I'd not expect the extra device to be a fuel shut-off solenoid (but can't be certain, though the connection to the butterfly valve would make more sense as a starting aid).
Honda's (& copies) have an ignition earth for low oil level shutdown & on/off ignition earth to stop the engine, not a fuel shutoff, while LPG conversions use a Garritson Valve (basically a vacuum membrane that only opens under induction pressure & shuts off the gas in the event of engine shutdown).

 

[Nomad]

I have had similar problems with linkages in the past. It's often very difficult to identify - then very easy to fix.

Assume nothing, just because a linkage is fitted a certain way does not mean it's right.

Any chance a previous owner took it apart and put it back together wrong?
Remove everything and put parts back one piece at a time might help pin-point the fault.
Link rods swapped in the past? Look at parts that move in an arc - have they been fitted 180* wrong so they lock up?

 

[Prajna]

I have had similar problems with linkages in the past. It's often very difficult to identify - then very easy to fix.

Assume nothing, just because a linkage is fitted a certain way does not mean it's right.

Any chance a previous owner took it apart and put it back together wrong?
Remove everything and put parts back one piece at a time might help pin-point the fault.
Link rods swapped in the past? Look at parts that move in an arc - have they been fitted 180* wrong so they lock up?

It has been serviced for sure because the air filter and spark plug are brand new. My mate bought it with the property because it was used to run a 3 phase water pump to pump 140m up from a borehole. He couldn't get it started and insisted the seller start it and fill the water tanks to prove it works. I guess they got someone to service it, so it may have been 're-engineered' or maybe it goes back together in a less obvious way than I've done it, though I can't see any alternative way to assemble the choke mech. It is as if something that's supposed to move in a radius has been put in backwards. I'll take the air filter off again later, take a photo and see if anything looks out of place.

 

[Blobber]

If it only needs a little squirt to get it going that would work for me! Id leave it alone and do something else

 

[Prajna]

If it only needs a little squirt to get it going that would work for me! Id leave it alone and do something else

All very well but first you have to take the air filter out and find the brake cleaner and then start it and then put the filter and cover back on. It has electric start (when I find a battery for it) and will be lovely when I can just turn the key instead of all that faff.