The Snake Pit : Stripping a Late 80's Carburettor

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Originally Posted By: Ducked
Bugger! Got a left-over washer.

This dropped free at some point during disassembly and I sort-of-assumed / hoped I'd find where it came from when I was putting it back together.

But no.

Really don't want to take it all apart again and go on an invisible-round-mark-hunt , though of course I should.

Thought it was from the accelerator arm pivot-bolt (which is called something misleading like "set-screw" in the Japlish manual) but the ID is not QUITE big enough.

I'll park it somewhere accessible meantime.

It's very likely from one of the pivot points. Go through my complete picture set and you will see where it's from.

It must be one of these guys:

IMG_0924.jpg
 
Originally Posted By: HosteenJorje
Lacquer Thinner. Gasoline residue doesn't stand a chance. Use in a well ventilated area far away from any type of ignition source.


I believe you, BUT:-

(a) I don't know the Chinese for "Lacquer Thinner"

(b) Its quite likely that Taiwanese don't know the Chinese for "Lacquer Thinner" either, and wouldn't care if they did. That won't necessarily stop them selling me something else "lost in translation" though.

(c) With brake fluid, I don't have to "Use in a well ventilated area far away from any type of ignition source."

In my situation that implies outdoors, which isn't optimal when doing this kind of theoretically-meticulous-high-screw-up-potential-tiny-evasive-parts job. It'll also involve large numbers of mosquitoes all potentially carrying dengue fever. (though they probably wont much like lacquer thinner either, which does give it a bit of an edge).

(d) Gasoline (or oil) residue isn't always the only, or main, problem. There are sometimes mineral-looking (corrosion?) deposits which carb cleaner (and I'd guess lacquer thinner) won't touch.

(e) You probably can't use a hypodermic syringe, my carb-cleaning weapon of choice, with lacquer thinner. That, for me, is a bust.

(f) Used brake fluid is FREE. I like FREE.

(g) Using brake fluid to clean carbs may encourage me to change my brake fluid more often, and maybe vice versa. Potential win-win.
 
Paint thinner (Varsol, Stoddard Solvent,mineral spirits)is a good degreaser but won't cut gasoline residue. Try acetone or one of the carburetor cleaners off the shelf.
 
I believe carburetor cleaner is mostly acetone. It will work but you will need a hard object like a screwdriver to remove the carbon deposits if any. Gasoline deposits should mostly come off except for a thin layer. Use eye protection when you are squirting it in case it bounces back to your eye -- it will burn like crazy and could cause damage.

I was able to completely clean an EGR valve entirely blocked off by hard carbon deposits by using brake-cleaner fluid and a slotted screwdriver once.
 
Above is probably all true, BUT y'all are rather pointedly ignoring my statements on this topic. (Its my F-ing thread, after all)

I don't currently have a problem removing tar in the carburettor.

I don't currently have a problem because DOT3 BRAKE FLUID HAS WORKED WELL.

DOT3 BRAKE FLUID (not brake cleaner) has several apparent ADVANTAGES over the volatile organic solvents listed above.
 
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Tried it today. Started OK but was idling at about 1700, and seemed to be on choke without the choke pulled.

Slackened the choke cable and fiddled with the various knobs and got it to idle about 900 apparently without choke.

Initially seemed to drive OK-ish but deteriorated rapidly and started stalling and cutting out, so I parked it up.

Tried plugging the pipe to the apparently broken dashpot in case it was contributing a vacuum leak, but didn't seem to make any difference.

I'll have another go tomorrow but can't spend too long on it 'cos got work to do.
 
Much better now. Wouldn't run at all this morning, so I'd completely screwed it up yesterday evening (A mistake to try and work into the mosquito happy hour) but a lot of fiddling about got it going.

The choke butterfly pivot axis (and the throttle, to a lesser extent) seem a bit sticky (didn't strip down that far) so that's maybe a future job, and it seems to be almost completely insensitive to the position of the idle screw, suggesting damage to the needle (which looked ridged) or seat.

Doubt I'll be able to get replacement parts.

Dunno about emissions or fuel consumption yet, of course, but I'd guess both will increase.
 
Originally Posted By: Gokhan
It sounds like you need to trade it in with a rebuilt one.


Dunno if that'll be possible.

Its now OK for drivability, but won't idle reliably below 1000 rpm and is happier about 1200, plus the exhaust might be a bit smoky (was clear before).

Might be a vacuum leak, and/or maybe the fast-idle dashpot adjuster thing (which I don't yet understand) is maladjusted.

More fiddling to follow.
 
Originally Posted By: circuitsmith
See if you can get a Weber DGEV carb with adapter.


For a 3-cyl 989 cc engine?

Think that might be a fairly unusual conversion, and (if an adapter is available or make-able), might need to be jetted way down.

Not saying it isn't possible, but I'd guess it wouldn't be plug-and-play.
 
Not plug-and-play, but more straight forward than one of those emission control abominations from the '80s.
It's easy to change jets on the DG.
 
Well, its a thought. It'd be illegal, of course, so there MIGHT be trouble with the six-monthly inspection, though as long as I didn't go to a govt testing station (as I had to when I lost my vehicle documents) I might get away with it.
 
Fiddled with handbrake + manually adjusted the automatic adjusters this morning, and then took it to try them out. Started up OK and ran fine for a quick circuit around campus, then started kangarooing badly in traffic. Limped it most of the way back, then it conked out and wouldn't re-start.

Strange cos it had a perhaps 30K run, including expressway, a fortnight ago and didnt give any trouble, and I havn't touched it since.

My best (but not particularly confident) guess is a blockage, but why now?
 
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Above not quite accurate. It'll start, but not run unless you keep blipping the accelerator. That's what it was doing before.

What would cause this remission-then-relapse pattern?
 
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Thinks: Thought I'd washed it all off, but I wonder if a residue of the DOT3 I "experimentally" used as carb cleaner could have attacked gaskets in the interim?
 
Originally Posted By: Ducked
Above not quite accurate. It'll start, but not run unless you keep blipping the accelerator. That's what it was doing before.

What would cause this remission-then-relapse pattern?

Probably a problem in the slow-speed circuit, such as idle-mixture-screw adjustment or a blockage but could be many things. It could also be a choke issue (supposed to be slightly open when cold and completely open when hot) but there may be many other reasons, including vacuum leaks, float and needle-valve problems, various emission-control-systems components (EGR, feedback or high-altitude air bleed, etc.), etc.

If the choke checks OK, I recommend you to buy a new carburetor as before since you are having so many problems fixing it.
 
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