Attached are some pictures... The first is the carb upside down with the cover removed. That is the float and i assume the jets (i'm not really sure)... The second picture is a closeup of the carb jets. You should be able to clearly make out the numbers. The third is a adjustment screw i found AFTER taking the carb apart, but i'm unsure of what it does... The fourth is a pic of the idle screw (easy to find) and a screw I did not notice until taking the carb apart...what it does is beyond me! It has a ? and an arrow pointing to to it (its hard to see, but at the bottom right hand of the screen) Anyway. I need some advice. My truck is running rich and getting crappy fuel mileage. I was going to rejet it to run leaner, but I'm unsure of what 3 jets I should change, to what number should I go, and will I even be able to find these jets anywhere in Cananda/USA. I did not notice that there was 2 other adjustment screws, and i'm unsure of what they do. Perhaps I should try adjusting the screws and all before I rejet. I'm at about 2000ft altitude, and Japan is sea level but has higher land as well, so should I really need to re-jet? Mabey the answer is in one of the screws? Any advise would be greatly appreciated and sorry for the long post!
Attached are some pictures... The first is the carb upside down with the cover removed. That is the float and i assume the jets (i'm not really sure)... The second picture is a closeup of the carb jets. You should be able to clearly make out the numbers. The third is a adjustment screw i found AFTER taking the carb apart, but i'm unsure of what it does... The fourth is a pic of the idle screw (easy to find) and a screw I did not notice until taking the carb apart...what it does is beyond me! It has a ? and an arrow pointing to to it (its hard to see, but at the bottom left hand of the screen) Anyway. I need some advice. My truck is running rich and getting crappy fuel mileage. My plugs are black'ish and smell like fuel. I was going to rejet the carb to run leaner, but I'm unsure of what 3 jets I should change, to what number should I go, and will I even be able to find these jets anywhere in Cananda/USA. I did not notice that there was 2 other adjustment screws, and i'm unsure of what they do. Perhaps I should try adjusting the screws and all before I rejet. I'm at about 2000ft altitude, and Japan is sea level but has higher land as well, so should I really need to re-jet? Mabey the answer is in one of the screws? Does anyone have a pic or a manual that shows what these screws do and what each jet controls (main jet, ext.)? Any advise would be greatly appreciated and sorry for the long post! -mark
be careful when rejetting! unless you know something has been done that requires jetting, like a bigger cam or something, i would much rather have it run rich than lean. unless you are making corrections for altitude. if it once ran well and now is running rich find out why? like a clogged air filter or something like that. if it runs rich it will foul plugs and get lousy mileage, but if it runs too lean you will ruin the engine. you will burn valves and over heat and other costly things. but if you must rejet, a good way to save money is going to be to open up the air correction jet. that will let in more air, and you can open it up rather than buying a smaller main jet. the best way i've found to do a jetting test is this... replace the plugs and let it idle. run it for a bit then pull the plugs and read them. if they are black and nasty your idle jet is too big. if they are a nice tan color the idle jet is right. after you put the plugs back in, take the truck out and run it on the main jet (usually above 3000 rpm) run it kinda hard and then pull the plugs and read them again. same thing goes here, if they are black it's running too rich, if they are a nice tan color your jetting is pretty good. as i have said before these motors are built for rpms, if you bog them you will have problems. the richest part of the power band is on the transition from the idle jet to the main jet, if you are always running it there it will give you a false reading of running too rich because it's pulling from both circuits. JMHO
looks to me like you're right about the top screw. It's definately idle. the second one with the yellow paint mark on it looks like it is for choke idle speed. The last one thats sorta hidden... does it lead to the throat of the carb? Highly likely that it is the low idle mixture screw. top screw- set it after the truck is warmed up yellow screw- set it to hold a higher idle from a cold start. looks like its still at factory spec. should be ok where it is. air/fuel screw- turn it in until the rpms begin to drop, then back it off 1/2 turn At 2000 feet you are not in a high altitude situation. I'm just over 2000 here and have never heard of any call for elevation compensation.
wow, thanks for the great posts guys! John Canfield, those drawings are great, but what model of truck are they from? FYI, mine is a 91 honda acty 660... LawnGasCaulk, great, great post as well. Thank you! The only problem I find is to change the jets is a PITA. It takes a good half an hour to pull the carb because of the plastic case around the carb, and all the vacume lines, and there is coolant entering from where the intake maifold and carb meet, so every time i remove the carb i lose a lot of coolant. Half of the carb adjustment screws are a PAIN to get at unless the carb is out, so you have to remove the card, adjust it, then re-install, remove and adjust, re-install until you get it right. VERY PITA! I might be able to get at the jets from the bottom of the carb IF i leave the plastic cover off the carb, just until I get it tuned properly. A last question, of the 3 jets show in the first picture(jet #1, #2 & #3) which one is the main jet, idle jet and where do you open up the air correction jet? Thanks kindly to all! -mark
Dan, the screw in picture #3 (the white plastic screw) is the idle air/fuel screw, right? I agree, at 2000ft its not exactly high altitude, so I will probably give the carb a good cleaning/tune-up before I start swapping jets. Thanks kindly, -mark
when i say open up the air correction, it has to be done with a small reamer and a jetting gauge. measure it first and open it up to the next size. if it's a 165 go 170 etc. you might be able to take it to a speed shop or a motorcycle shop and they can do it for you, i always did it for free when i ran a speed shop. if i were a betting man i would say 35 is your idle 160 is your main and the other is the air correction. jmho, good luck
Regarding Mini Truck specs and info... Hello, I figure you folks might have been to this site although I am going to mention it in the case that there are folks like me that are too lazy to go through all of the threads... There is a website... LuLu dot com that sells English versions of the service manuals for the Suzuki and the Daihatsu's for a good price. I am a dealer in Caldwell, Idaho and and until I was turned onto this site, I was reverse engineering these things as well as living off of "Tribal Knowledge". These manuals are great. I advise that you folks that have not... go to the site and take a look. Thanks Cory Gahley
Doh! Sorry about that. The site is LULU do com. I inadvertently threw in an s where it should not have been. Have any of you folks come up with an aftermarket air filter and a reasonably priced snorkel so we can get the air intake out of the dirt? Thanks. ATVAlternatives.
This looks very similar to a motorcycle CV carb - and I can tell that it's a CV carb because of the large diaphragm housing on top. In the first photo, jet #1 is the slow jet (also called the pilot jet), jet #2 is the choke jet, and jet #3 is the main jet. I can tell in the photo that jet #3 is exactly the same style of Keihin main jet that practically any motorcycle carb that uses Keihin carbs will use (Honda and most Kawasaki models). In fact, I can tell that it is a #160 Keihin jet from the second photo. In the second photo, you have not separated the jet itself from the emulsion tube. Don't mess with the emulsion tube. I am not 100% sure what the circled adjustment in the third photo is but I am pretty sure it is the idle mixture adjustment screw. The external screws that act on the throttle linkage have to do with the idle speed and shouldn't affect fuel consumption. This particular carb has a lot of extra gizmos and gadgets that a motorcycle carb doesn't have (automatic choke, etc). I cannot comment on how any of that works ... If you take off the 4 screws on the top of the carb and remove the diaphragm housing, you will find that there is a vacuum slide in there with a needle that projects down into the emulsion tube that comes from the main jet through an orifice in the top of the emulsion tube (this is the "needle jet"). This varies the amount of fuel going through the needle jet as the vacuum slide moves. More air through carb ... slide moves up ... opens needle ... lets in more fuel. The shape and position of this needle change the fuel delivery curve at moderate load. The air jets will be facing the inlet of the carb. Normally there will be 3 of them - main, slow, choke. You can figure out which one does what by blowing carb cleaner through it ... which you should do anyway to make sure they are clear, because deposit build-up in the passages WILL make it run rich. Most common causes of a CV carb running too rich: - Incorrect float level - Blocked air jets or air jet passages - Choke not opening/closing properly - Broken needle in the idle mixture screw adjustment, usually because someone jammed the adjustment screw closed too hard and broke it. - Dirty air filter - Restricted air intake If you look in the outlet side of the carb with the throttle closed, you should see some tiny holes right next to where the throttle blade is. As you crack the throttle open, it uncovers more and more of those holes. The hole that's open all the time with the throttle closed, is the passage for fuel at idle. The idle mixture adjustment screw will be right outside that passage. If you can't find anything "wrong", try to establish under what load conditions it is running too rich ... this will help fine-tune what adjustment needs to be made.
