rebuilder86 Posted February 2, 2016 Report Share Posted February 2, 2016 (edited) 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. Edited February 2, 2016 by rebuilder86 Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted February 2, 2016 Report Share Posted February 2, 2016 Certainly the richness will help it resist pinking, but 4Ks will carry a lot of advance without knocking at all. Just see how it goes. You might find it is too advanced at low revs. Once it is running OK get a timing light and mark the pulley with white ink out to 40deg. Generate a timing curve up to 3000rpm, then take a spring out of the dizzy base and replace it with a lighter one. That will allow you to retard the idle advance back to 10deg and still have it advance up to 35deg in the first few thousand rpm. http://www.rollaclub.com/board/topic/49927-how-to-fix-your-brand-new-ke-motorsport-electronic-distributor/page__pid__511594#entry511594 Quote Link to comment Share on other sites More sharing options...
rebuilder86 Posted February 3, 2016 Author Report Share Posted February 3, 2016 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 Quote Link to comment Share on other sites More sharing options...
bruce Posted February 4, 2016 Report Share Posted February 4, 2016 I had a similar issue with my 4K. I had to set the timing to around 20 degrees so it can run better (missing under load). Replaced a lot of parts like points, ignition leads, distributor cap, and coil etc. Ended up being worn advance weights in the distributor. Swapped the distributor and it was good. Actually get less fuel economy now. Probably driving it harder. Does have a rough idle that I can't tune out, probably the old 3k carby that is on it. I've set the timing to 10 degrees now. I did have an issue for the first 15 minutes when driving, it would run rough and stall at a stop. That was on 91 octane. Have changed to 95 octane and haven't had a problem since. Found that 98 octane didn't burn well and made the plugs sooty causing a weak spark. Quote Link to comment Share on other sites More sharing options...
rebuilder86 Posted February 6, 2016 Author Report Share Posted February 6, 2016 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? Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted February 6, 2016 Report Share Posted February 6, 2016 I expect that part to be an emulsion tube to mix the incoming air with the fuel, but I haven't pulled a stock carb apart to check. The factory listing is 21205 Jet Sub-Assembly, Slow 21024-61060 ID=0.55 I'm not sure why the Yanks call them "slow" jets, I think they are air jets. So you get primary and secondary jets in their respective throats, and they are made up of main jets and air jets. The extras are power jets in the accelerator pump and idle jets for idle. Quote Link to comment Share on other sites More sharing options...
rebuilder86 Posted February 7, 2016 Author Report Share Posted February 7, 2016 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 Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted February 8, 2016 Report Share Posted February 8, 2016 Well, that tip is not in this strip, look at 3min in. He does say they are called 'slow' jets by Toyota, but they are air corrector jets in reality. The number is their flow size, and the bigger number will add air to a larger amount of fuel. That diagram has only one of those air correctors, and I expected one for each throat. It also doesn't have an idle jet labelled, so I think its not a full picture of the carb. Do you have two of those jets in the carb? I'm going up to The Woolshed this Wednesday to work on my 4AGE conversion, so if I get time I'll pull a 4K carb apart. Only then will it make sense to me. Quote Link to comment Share on other sites More sharing options...
rebuilder86 Posted February 8, 2016 Author Report Share Posted February 8, 2016 (edited) 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. Edited February 8, 2016 by rebuilder86 Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted February 8, 2016 Report Share Posted February 8, 2016 Jet 4, Pinhead calls it the power jet, Yep... It's for extra fuel above the accelerator pump when you boot it. The rod is vac operated I think and opens the jet to fuel flow. Somewhere in there is the accelerator pump setup with its little ball bearing and spring. Its a one-way valve to fill the fuel pump cylinder ready for use and to stop the fuel bleeding back into the bowl. What I usually do with carbs is to use a 5cc syringe without a needle to push petrol through all the drillings in the body. Sometimes they will block up with gunk so it won't work even if the jets are clean. Quote Link to comment Share on other sites More sharing options...
rebuilder86 Posted February 9, 2016 Author Report Share Posted February 9, 2016 yeh the accel pump is too easy, know all about that one from my high school days in mechanical workshop!! Only teacher whoever taught me anything worth knowing! My trick is to stick the little stray from a can of degreaser into the orifice and spray it and watch where it comes out. I never saw anythign come out of the power jet hole though. probabyl because it chose the main primary jet as it was closer to the source of pressure. Now i might check that power jet is functioning properly. I did ponder over the idea of this jet last night, and started to get upset wiht myself for thinking that rod was just there to push that spring down with no other purpose haha. Quote Link to comment Share on other sites More sharing options...
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