rebuilder86

There are 4 jets in total. Jet 1. one at the side of the fuel bowl on the primary throat side which supplies fuel to the primary venturi and the idle circuit cavity Jet 2. the long spear jet for the idle circuit which gets its fuel from the cavity after jet 1. Jet 3. one at the bottom of the fuel bowl at the secondary throat side, which supplies fuel to the secondary venturi Jet 4. One underneath a spring in the middle of the fuel bowl on the side between both throats where the spring is pushed down by a push rod attached to the fuel bowl cover, I have NFI what this jet does. I personally think its jsut there to make it look complicated and piss people like me off. (shown as part number 21255 in the diagram) I should point out, that parts diagram is not my exact carb, its similar. Mine doesn't have that external Hot Idle Compensator Box with vacuum lines coming out of it, mine is built inside the carb. It seems this diagram doesnt show the primary or secondary main jets. EDIT: Jet 4, Pinhead calls it the power jet, so i guess its just a way of getting more fuel into the primary and secondary venturies.

sorry i don't follow your reply.... Are you saying that you expect the missing part to be the emulsion tube, or that the part in that diagram is the emulsion tube? Are you saying you think that part in the diagram is not the idle jet? that you expect it to be something for mixing fuel and air? if so, fuel and air for what: idle or primary or secondary venturies? The part that appears to be missing, is shown at this time in the following where this guy is taking apart an almost identical carb. He takes out the spear, and pops off a little cylindrical bit, the bit that i am missing. Do i need it? I think it is the emulsion tube and idle jet as one piece. and then an inlet filter on the end, which i am missing. The end of the spear must still be under the fuel level otherwise i wouldn't be getting any idle at all. But i wonder if this cylindrical filter part will help at all. Altezza you seem to be a very good source of information on this topic, i hope you don't mind if a bug you a lot for answers to questions... the internet is full of armchair experts who claim to be experts because they once put carb cleaner through their engine :P

i did have a big response typed out, but the fu&%ng website stalled and went grey when I tried to add a picture and there was nothing i could do to save the text i had typed. I CBF typing it again. Result.. No pinging still better powercurve less fuel smell from exhaust n However I found a part which seems to be missing from carby, the idle jet filter barrel thing which I have seen in youtube videos, which lives on the end of the idle jet spear. However it appears to be also missing in the following part diagram, its supposed to be on the end of part number 21205 (JET). Anyone know why some models have this part and mine doesnt?

yeh good idea. however, I'm in a land of fools and there is no chance of finding a spring on this entire island. When something breaks here, they don't consider it "no good" untill it completely stops functioning. Seems to idle bloody well when the manifold vac advance is connected and my timing light shows it at about 30-40 degrees at idle. I have no idea what RPM, as a tachometer is too much to ask for in this country. Certainly low enough to be almost inaudible. Will take for test drive today as is and see how it goes

Just use boiling water and a stiff bristle brush, with no pressure, or a car sponge with lots of pressure.

I thought i would share a story with you all. I'm living in the Philippines and i have an owner type jeep with a 4k engine. The carb i purchased 1 year ago seemed to give me realy poor fuel economy, however better than the forklift carb that was installed in it previously. I've been mucking around rebuilding the carb numerous times, each time finding horrendous problems: 1. fuel bowl cover gasket had hole for idle circuit 5 mm off from where it is supposed to be, so effectively there was no idle circuit 2. fuel inlet valve was full of gunk 3. fuel float level had been tampered with And just now after getting it running quite well and countless trips over the hills worrying about my 13+ L / 100Ks fuel economy, I find the jets where swapped. Primary where the secondary was supposed to be, and vice versa, so a bigger primary than the secondary. I suspect the monkeys who had the carb before were trying to make it more powerful, without actually knowing anything about what they were doing. I have not yet test driven since I swapped them back, but it has got me thinking about a few things... I have had my base timing set at 19 degrees (nill vac advance) and have never experienced a single ping or knock. Could this incorrect jetting be the reason for this? in other words, overly rich??? Here's to hoping I am closer to getting this thing running well.

Stop! it was probably just painted in an acrylic. Boil the kettle and pour the kettle over the spots numerous times, then wipe of the melted acrylic with a car sponge and a heavy pressure.

see i only have one vac advance port on the damn carb haha. and I know it is the correct port. but its just not putting out enough vacuum to pull the diaphragm in the can. The other is not on the carb, but on the adaptor plate between the carb and manifold, and it has TOO MUCH vacuum constantly. I'm starting to think, testing the manifold vacuum without engine load, doesn't reveal the correct results, but there is no intellectual discussion of this, anywhere in the entire web. I don't really want to just trust my brains analysis of it, i want to hear from someone else who knows.

Hey all. This is a bit of a hairy one. I am living in the philippines and drive what is known as an "OWNER TYPE JEEP". These things are built in the jungle and nearly al are made with the mighty 4k engine under the hood. Mine was bought second hand and has been nothing but trouble. I got myself a 4k carby to replace the forklift carburettor some monkey had retrofitted but this carby that i bought is the most simple f all the 4k carbies i have seen online. It simply has one vacuum port from just next to the fuel inlet which I have taken apart and confirmed is connected to the vacuum port just above (before) the throttle plate, There is also one well below the throttle in the rubbery adaptor plate between the carby and the manifold. (manifold vacuum). I can not get my vacuum advance to work properly. Now, I have myself an electronic distributor with working mechanical advance and 2 vacuum advance ports, my research tells me one is for ported and one is for manifold. Other research revealed that most people simply block one of these ports off and simply connect the other to their vacuum port of choice. This makes no sense to me and I want to do it properly. I suspect this lack of vacuum advance is giving me economy issues; as my Jeep is using about 13L/100k, when I should be getting at worst, 10L/100ks. Based on tests with my timing light, I have come to the conclusion that the vacuum supplied from the manifold port (under the carby) is too much and never varies. With the mechanical advance jammed (ziptied shut) the timing stays at a solid ~40 degrees BTC with the vacuum from this port. attached. When opening the throttle, this does not change. This indicates to my brain, that either a. this carburettor is too sensitive to vacuum advance, or b. I'm not testing it properly. Now moving on to the ported advance. This has the opposite problem. I know there is meant to be nill vacuum at idle and a blip of the throttle should cause a blip on the timing (more advance). I am seeing the opposite of this, and at very most I'm seeing a 0.5 degree retard when i blip the throttle. Nothing i can do with the ported vacuum will make any advance happen. This indicates to my brain that either: a. this distributor is not compatible with this carburettor, (not enough vacuum to operate it) or b. the carburettor is ill manufactured and the ported vacuum port is to small to generate enough vacuum. So my general consensus, which I would love if someone knowledgeable could verify: I need to increase the ability of the ported vacuum source to supply vacuum when the throttle is just open, by drilling out the external aluminium plug behind the port and drilling out the port to a larger size and the re plugging the external plug. I then need to increase the spring tension in the dizzy advance to overcome what appears to be an oversupply of vacuum. other info There are no other vacuum systems in operation other than the brake booster and PCV valve. The carburettor is clean and rebuilt by me (3 times with a bit more effort each time) and I can 100% guarantee it is at factory condition and is producing as much ported vacuum as it possibly can in its currently engineered state. I have no idea if the dizzy is a 4k or 5k dizzy, I only know it is electronic, has 2 vacuum advance ports, both are definitely advance ports and it produces a great spark. I can not determine what the difference is between my carburettor: and this common variant: or this other variant with numerous vacuum ports Anyone able to shed some light on this for me?