Carburetor overhauls

I think I brought this topic up at least once in the past 10 years or so, but now have an incentive to do so again.

The carburetor on my Freeca van has finally choked (on dirt, presumably) and died. The van will start and can be driven, but it won’t idle. Fiddling with adjustments this time is not going to be enough - I need either:

A) A new carburetor, or
B) A carburetor overhaul

I’m told that a new carburetor would cost something like NT$7000-plus, so the financial incentive is to overhaul it. Everything I’ve gleaned from mechanics in Taiwan is that they don’t like to do overhauls, because they usually turn out poorly. But back in ancient times when I lived in the USA, I actually did carburetor overhauls myself, numerous times, with a pretty good success rate. The key difference between here and there seems to be that Taiwan is plagued with crappy:

A) carburetor overhaul kits / huàyóuqì xiūlǐbāo 化油器修理包
B) carburetor cleaner / huàyóuqì yàoshuǐ 化油器藥水

Now I could be wrong about all this, and I’d love to hear from someone who has actually done a successful carburetor overhaul in Taiwan. What I was told (admittedly, secondhand experience) is that the carburetor overhaul kits sold in Taiwan are just a set of gaskets. But there are other parts in a carburetor that ought to be replaced in an overhaul, in particular the needle-and-seat valve that controls the level of fuel in the float bowl. It’s not like you can just fix the old valve with a file or sandpaper, it’s a precisely machined part. Another part that should be replaced is the accelerator pump, but that’s probably not the part that is causing my current problem (my acceleration is still pretty good). There are some other parts in a carburetor that can wear out (such as springs), and those ought to be in any decent kit. If I can’t get a new needle-and-seat valve, I’ll just have to hope that the old one is OK - the fact that the carb won’t idle may be due to plugged jets or one of the other numerous holes and passageways in the carb.

The carburetor cleaner problem is even more incomprehensible to me. It’s just a chemical solvent sold in any auto parts store back in The Old Country (the USA). It seems that the Taiwanese just use that spray-on crap, which is useless. I’ve described in detail to the auto parts store owners what I need, and they just say “meiyou.” But it seems to me that maybe I can substitute some kind of industrial solvent for the special-purpose chemical we use in the West. However, I don’t know what I can buy locally that would do the job, so I’m asking for suggestions. The cleaning naptha that is sold in gas stations probably isn’t up to the task - it’s really good at dissolving grease and sticky glue, but to dissolve carburetor crud and gas varnish, I probably need something corrosive. I’m thinking that the acid they use for cleaning toilets might be my best bet - just hope it won’t dissolve aluminum.

cheers,
DB

Don’t use acids, you’ll just bugger things up, and the glaze isn’t necessarily acid-soluble anyway.

Use lighter fluid for zippo, or similar, and a toothpick to scrape stuff off and open passageways.

and new gaskets, etc. are easy enough to get. The needle valve and seat may be available on amazon etc. However, if the slide has worn the surfaces of the cylinder it slides in, then you’ll never get it working properly, no matter how clean it is.

I cleaned my motorbike carb last week with that spray and all the original parts and it hasn’t mad any difference. Went to the shop yesterday to see if they could get it to idle properly and they couldn’t. They said the carb is working fine, which it obviously isn’t, as they couldn’t get it set up properly. I didn’t think getting a new gasket set or overhaul kit would be possible or necessary (it’s only done 8000 miles). I’ll watch this thread with interest because I too don’t fancy buying a new carb.

I’ve done it a few times with motorcycle carbs, on a Kymco Zing, and Yamaha RZR. Always because of my neglect. I hadn’t run the bikes for a while and the carbs clogged up. That’s probably the situation again but I havn’t investigated yet.

These motorcycle carbs were likely much simpler than a late model car carb, which’ll have all sorts of anti-pollution circuits and gizmos on it.

The last time I tried to understand my 1986 Daihatsu Skywing carb (the engine was suffering from a runaway idle) I got a headache, and my choke stopped working, though I did get rid of the fast idle. I dont relish the thought of stripping/cleaning it.

This is not a recommendation, just what worked for me.

I boiled them in water with washing powder in it. This seems to etch the carb body, so you shouldn’t overdo it, though its possible there was some galvanic action with the aluminium pot I boiled them in, so perhaps stainless steel or , better, enamel ware, would be safer.

I’d previously removed the jets and needles and soaked them separately in a small bottle with 3M carb cleaner in it. I don’t rate that much as a spray but its fairly effective on tarry deposits as a soak. I shook the bottle periodically and rubbed it against another bottle, which generates ultrasonics.

Most of the gunge wasn’t tarry, but a gray powdery, almost mineral-looking sludge which wasn’t touched by the carb cleaner. Gross cleaning was by toothbrush, but small passages required blasting out with detergent jets from a 5 or 10 ml hypodermic syringe with a fairly widebore needle. Get the type with a screw-on needle or it’ll blow off under pressure and you get crap in your eyes,/ a needle in your hand, though of course I wasn’t daft enough to do this without eye protection. AS IF…

I think the most clogged passages I had to resort to a fine needle blasting inside the passage, though that’s risky.

This worked, but I didn’t have to replace any components and its a minor miracle I didn’t loose any tiny bits. I did manage to put the float in upside down though.

Twice.

Original thread on the above, Longer ago than I realised. :frowning:

forumosa.com/taiwan/viewtopi … er#p798445

I’ve done some googling around and hit upon similar threads in other forums in various countries. Most helpful suggestions came from a forum based in Sweden (seems like they don’t have carburetor cleaner either). The suggestions from the audience (in order of most-likely-to-succeed) included:

antifreeze (heated)
lacquer thinner
acetone
toluene (toluol)
MEK (methyl ethyl ketone)
brake parts cleaner
denatured alcolol
detergent in water (heated)

Some of these substances are quite hazardous - MEK in particular. Toluene can get you high (and cause brain damage in the process). Everything except the antifreeze and detergent are pretty flammable.

I will probably start my carburetor experiment with lacquer thinner 香蕉水 (xiāngjiāoshuǐ) because I happen to have some in my storage shed. Antifreeze is mostly ethylene glycol, which is supposed to be a good cleaner, but it’s a bit expensive, plus it’s suggested that it be heated to 180°F (82°C) and kept that warm overnight. Actually, ethylene glycol becomes flammable if it’s heated to it’s flash point: 240°F/115°C, so be careful if you try it. Keeping it warm can be tricky - would probably require putting it in a rice cooker, and I’m not sure my wife would like me to use her rice cooker for that.

Sometime this weekend I plan to tackle this, and I’ll report back.

cheers,
DB

[quote=“Dog’s_Breakfast”] But there are other parts in a carburetor that ought to be replaced in an overhaul, in particular the needle-and-seat valve that controls the level of fuel in the float bowl. It’s not like you can just fix the old valve with a file or sandpaper, it’s a precisely machined part.

DB[/quote]

This isn’t exactly wrong per se, but (based on my experience of motorcycle carbs only) I think the emphasis is wrong and MAY be based on a misunderstanding. Apologies in advance if that is not the case.

I think the needle and seat valve is basically an on-off “switch”, so, while it has to work, its not really a precision control item. If it leaked, your carburretor would flood. This would most commonly be because there was some hard muck on the seat stopping it make a seal, though its also happened to me when I put the float in upside down. :blush:

If it stuck, (probably because of sticky muck) you’d suffer fuel starvation, perhaps intermittently. I don’t THINK either case is likely to cause idling problems. IIRC some float valve needles are actually rubber tipped. Its viton rubber, and no doubt quite carefully moulded, but its not really precision machining.

I’m guessing you may be thinking of the metering needle. That, and the nozzle it fits into, are both precision items, and need to be treated with care. For motorcycles, new /alternative metering needles are certainly available, since bikers are obsessive about carb “jetting”. I’d have thought they’d be available for your car too, but possibly they aren’t readily available in Meio-Too-Old-And-I-Can’t-Be-Arsed-Taiwan. If that carb is in use overseas (Malaysia? Japan?) those parts are tiny and shouldn’t cost much in postage, if you can find someone to sell you them.

[quote=“Dog’s_Breakfast”]

“. I’m thinking that the acid they use for cleaning toilets might be my best bet - just hope it won’t dissolve aluminum.”

DB[/quote]

Remember that bit in Alien when they cut the face-grabber? That toilet stuff is concentrated hydrochloric acid and will solve all your carburretor problems permanently.

I think its quite important when removing the jets to have a good set of small/precision screwdrivers and spanners, because they are quite soft brass, and if the tool is at all mis-fitting you could easily distort them.

I gave them a good blast with WD-40 and left them overnight. Havn’t tried it yet, but, IIRC, I’ve been told/read somewhere that a 50-50 mix of ATF and acetone does a much better job as a penetrating oil.

To those anxiously awaiting my report: Sorry, I haven’t started the carburetor overhaul yet because I haven’t found a carburetor kit yet, but I haven’t been looking too hard either because I’ve been awfully busy with two other projects (ie cutting a very big lawn, and painting a house). Since we also have a Zace pickup truck, we’ve been driving that for now while the Freeca sits awaiting my attention. But I will get to it this week.

[quote=“Ducked”]I think its quite important when removing the jets to have a good set of small/precision screwdrivers and spanners, because they are quite soft brass, and if the tool is at all mis-fitting you could easily distort them.

I gave them a good blast with WD-40 and left them overnight. Havn’t tried it yet, but, IIRC, I’ve been told/read somewhere that a 50-50 mix of ATF and acetone does a much better job as a penetrating oil.[/quote]

My experience with carburetor overhauls in the distant past has been that no penetrating oil is necessary, though it wouldn’t hurt to use it. Jets are made out of brass because brass doesn’t corrode, but the threads of the jet do adhere tightly to the soft aluminum body of the carb. Agreed, the screwdriver must fit snugly in the groove of the jet, and you need to press very firmly while turning the screw counterclockwise to break it loose. Even if the jets are damaged in the process of removing them, that shouldn’t be a problem because a good carburetor kit will come with new jets (whether or not Taiwanese kits have them, I’ll find out shortly).

Googled for a few images of carburetor kits, and I’ve posted a couple below. Content varies quite a bit depending on the type of vehicle, as well as the quality of the kit manufacturer.


Chevrolet


Ford

Last successful carburetor overhaul I did was a few years ago on a lawnmower. But last year I tried to overhaul the carburetor on my chainsaw and it was a failure - I couldn’t get a proper kit and even had to resort to making my own gaskets.

Sounds like my experience is more limited than yours, limited to Mikuni-clone motorcycle carbs, in fact, but based on that limited experience, an overhaul kit, while its probably worth using, isn’t necessarily required.

I never had one, and the carbs worked OK after cleaning.

I can’t remember what I did about gaskets, probably just re-used them. I can remember that the RTV silicone I had at the time softened in petrol, so after experimenting I didn’t use it. On various occaisions I’ve cut gaskets from lay-flat hose material, (a black polythene sheet available in various thicknesses and widths, lying around in a rice-field near you.) but I don’t think I did that with the carbs. If I had, I’d have probably boiled the gasket just before fitting, to soften it and hopefully persuade it to conform to the surfaces better.

OK, here’s the status of this project/fiasco: bought a carburetor kit for NT$1100 (expensive, but it’s imported from Japan). Should have looked inside the package first - it’s missing the parts that are probably causing my problem. I’ve sort of determined it’s the idle-mixture screw, and that should be in a good carb kit but wasn’t in this one, so I’ll return it. I took the van to a mechanic friend of mine, and he looked in his junk pile and pulled out an idle screw from another similar carb, put it in my carb, and at least now it can idle (which it couldn’t before). It’s really not the right part, but beggars can’t be choosers and at least the beast is drivable now. Well, actually not - while I was at his shop, my radiator suddenly started leaking badly. I already knew it had a leak, but since it was hot from the drive to where he lives, it suddenly became a geyser. So new radiator (NT$3000).

This is just about the last repair I intend to make on this piece of crap. I have nothing good to say about the Freeca, and wouldn’t recommend it to anyone.

Does anyone have anything good to say about Mitsubishi? I had it in mind that maybe I’d someday get a Delica truck (I like their heavy-duty capacity), but now my confidence in Mitsubishi is shaken. I’d buy another Zace, but alas they are no longer being manufactured.

[quote=“Dog’s_Breakfast”]
Does anyone have anything good to say about Mitsubishi? I had it in mind that maybe I’d someday get a Delica truck (I like their heavy-duty capacity), but now my confidence in Mitsubishi is shaken. I’d buy another Zace, but alas they are no longer being manufactured.[/quote]

Redwaggon had good things to say about the Delica, IIRC.

I know you’ve got a direct comparison available with the Zace, but that’s a Toyota. Most cars do break occaisionally when they get old.

Isn’y 3K rather a lot for a scrap radiator?