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Carb adjust

Discussion in 'Daihatsu Hi jet' started by cdover73, Dec 28, 2015.

  1. cdover73

    cdover73 Member

    I just installed the new carb from my other post that I refuse to re-open, so I figured I would start a new one here on this specific issue. I watched Fupa's video a few times and have a good understanding of the settings and their functions. The problem I am now having is the idle controls.

    On a cold start, I pump the pedal once or twice and it fires right up without hesitation. Then it SCREAMS at 'idle'. When it warms up and the choke opens, it bogs and dies. It's at the extreme ends of the spectrum on both sides. I can't seem to find the sweet spot to make it idle like he did in the video.

    What I have done:

    I installed the carb and didn't touch anything as it is supposed to be test ran and adjusted pretty close off the shelf. Once I saw how it idled I started tweaking per Fupa's instructions.

    First, I verified all the adjustments were about where he said they should be and they were. At cold high idle I backed off on the small setting screw for cold idle. I had to back all the way off to get it to respond at all. I screwed it back in a few turns. By this time the wax element melted and the choke opened. So I moved to the big screw and was able to get the idle back to reasonable rpm's. However, it surges and if I blip the throttle it will not stay running. I have to increase the big screw until it idles. The warmer it gets the more I have to screw in on the big setting to make it stay running. BUT, that means at cold start after the truck sits a while it is over-revving again because the air/idle is too far in from the 'hot' setting the last time it ran.

    I screwed the choke setting (in front of the throttle cable bracket) all the way out until the choke opened. Then I screwed it back in while watching the choke blade until it touched/closed. I went about 1 more complete turn and left it there.

    I unscrewed the throttle stop all the way then back to touching + 1.5 turns. Just where it felt positive resistance.

    With these settings adjusted per the video I am left with only the big screw air/idle adjustment to make any changes. I literally have to adjust it as I drive the truck, stopping occasionally to turn it in or out.

    Also, when I do have the setting adjusted just right where the engine idles around 1200 or so rpm's, it is very touchy at slow speeds. If I'm driving the deer trails around my property and in either 1st high or 2nd low there seems to be a dead spot in the throttle position. Almost like the gas is either on or off. This causes a bucking sensation and will cause the truck to die. Very frustrating to drive like that.

    Valves and timing are spot on. No vacuum leaks verified by my vacuum gauge bouncing steady around -18 in/hg and WD-40 sprayed over the hoses. Compression is 160, 162, and 180 for 1, 2, and 3 cylinders, respectively. That was actually tested when I had the overflow problem. I expect gas was washing the cylinders, so I would probably have a little higher on each now with the rings properly lubed and no fuel sitting on them.

    What am I doing wrong, or what should I try? Is there a trick to finding the proper setting? A combination of "screw in on this, screw out on that"?? Any advice will be greatly appreciated!
     
  2. TRAX and HORNS

    TRAX and HORNS Well-Known Member

    Following fupa's instruction should get you close.
    Something could have been in fuel line and entered carb. ? Fresh new fuel? Clean air filter? (Blowing out a saturated air filter will throw a wrench in the spokes). Recently had a customer that had a bogging issue. Truck would start fine, idle fine, but if you gave it any fuel at all before coming up to run temp. it would run way rich, bog down, blow black smoke. All I did was install a new air filter, problem solved. Old filter looked ok but was no doubt stopped up.
    The simple little things will eat your lunch sometimes.
    The couple of carbs. I've ordered from Yokohoma Motors have been dead on but there is the possibility that something was not right inside.
    My suggestion is to contact James or Don at Yokohoma motors and pick their head on settings.
     
    Last edited: Dec 28, 2015
  3. cdover73

    cdover73 Member

    I had an issue when I installed it. There was trash in the needle seat that was causing it to overflow. After pulling the float and fixing that I don't have any more overflow problems. But with that said, yes, there could be trash further in.

    The air filter, engine filter, engine oil, spark plugs, and fuel are all new and fresh. I cleaned the tank out good while I was waiting for the carb and blew all the lines from back to front. The fuel pump is new and I have a regulator installed just before the carb and set to 2 psi.

    The truck runs perfectly fine if I adjust the air/idle setting as it gets up to temp. I start with it backed out so it doesn't over rev, then screw in on it periodically as it heats up. Eventually I end up with an engine that runs perfect as long as it is at it's highest temp and the carb is adjusted for it. If I let it sit and cool then I have to start all over with the big screw. It seems like I don't get much of a response or change if I move the other adjustments around. I did find that I could screw the choke setting all the way in and back out on the air/idle screw to where it idles properly then there isn't as much of a range as it gets hot. Meaning I only have to adjust a quarter turn at a time instead of a full turn. But I know it isn't meant to run with the choke that tight. The small cold idle adjustment does nothing to bring the idle down when it's cold. Right now it is screwed all the way out. I don't understand this as that is what it is there for.

    I can live with it as it is. I will eventually find a sweet spot as it breaks in and I get more used to the new way of driving it. But I would like to eliminate that and have a truck that cranks and idles properly throughout the temp range.
     
  4. TRAX and HORNS

    TRAX and HORNS Well-Known Member

    have you read the plugs since messing with it?
    If not, for grins pull them clean'em up and then run the truck for 30 min. And read them again. Black is rich , white is lean, nice tan c0lor is where you want to be.
    Is the little plastic cap still on the air screw? If so you might pull it off and that will let you adjust it more than a half turn. Typically that air screw is for fine tune, getting the rough idle cleaned up.
     
  5. cdover73

    cdover73 Member

    Good idea! And I think I may be calling things by different names. The air/idle I was referring to is the bigger of the two idle adjust screws. The one with the plastic cap, which mine doesn't have, is fine. I have it tuned as smooth as I can get it. It's the two to the right that I am having problems with. The smaller one on the choke actuator is supposed to adjust cold idle. Backing off is supposed to decrease and prevent the high idle when the choke is closed. I backed it all the way out and it only settled down a tiny bit. The bigger one is the main idle adjust and the one I am having to constantly adjust to maintain proper idle. The half turn screw on top is not being adjusted.

    But I will check the plugs. I am running a funky E3 plug. It has 3 ground electrodes and the gap can't be adjusted. It's all the parts store had at the time. I may go to an equivalent Champion plug if these don't perform well. I had NGK's in it before and they fouled all the time. Not happy with them at all.
     
  6. cdover73

    cdover73 Member

    Okay, I got it running decent again. I had to screw the choke adjust all the way in and back out on the main idle adjust (large screw) until I found a sweet spot where it idled good cold and hot. I'm sure this isn't the way it is supposed to be setup, but it's the only way I can get a clean idle at all temps. It'll do for now.

    I talked to Don at Yokohama and he told me the carb will never run right with the electric fuel pump installed. He said I would have to go back to the original mechanical pump that has the proper supply and bypass. Until then he couldn't help me. I understand his stance, but my argument is still 'why did it run so good for two years if the electric pump was the problem'?

    Regardless, it's running back to somewhat normal with better acceleration and starting than before, so I don't regret the move to buy a new carb. I am now in the market for a replacement with EFI.

    Thanks for the support!
     
  7. ttc

    ttc Active Member

    Yes I wish I could of found a efi hijet when I got mine from the auction house in Japan.
     
  8. ttc

    ttc Active Member

    When you had your carb apart did you notice if the main needle could be removed and shimmed?
     
  9. cdover73

    cdover73 Member

    Are you talking about the main jet with the offset holes down it? I did pull it out and clean it, but I'm not sure if that is what you are referring to. You have to excuse my ignorance. I know every part of the carb by sight but not sure if i know the proper terminology. Description maybe?
     
  10. ttc

    ttc Active Member

    The actual needle that slides in and out of the main jet
     
  11. ttc

    ttc Active Member

  12. cdover73

    cdover73 Member

    Oh! I don't have that carb. My carb has the choke actuator mounted to the side and does not have the large dome on top. The part number from Yokohama for mine is 87B54. I think it's the one before your model. See the pic...
     

    Attached Files:

  13. Tori Bean

    Tori Bean New Member

    cdover73....sounds like we are having similar problems. Had my truck running good but somehow ruined it. I have an electric fuel pump with a regulator installed. The regulator is currently set as only 1psi. Do you think that may be too low? What is yours? Also it seems as my choke never opens up, and the truck never idles down when warm. I have been fooling with the adjustment screws for weeks now & don't know what to do. It will seem to idle ok, but then almost die & sputter when accelerating from a stop. Its drivable but not as nice as it did before. Any suggestions would be greatly appreciated!!! Ive attached a pic of mine, been using the 2 circled screw to try adjust, not sure what the smaller one does or if it needs adjustments. I did rebuild the carb this year, so nothing should be too gummed up or stuck! carb:adjustments.jpg
     
  14. ttc

    ttc Active Member

    Another thing is the valves can affect how the engine runs. Have you checked the valve lash.
     
  15. Tori Bean

    Tori Bean New Member

    I haven't but have been meaning to, I'm just assuming something I did when adjusting the carb and fuel regulator is the reason its not running good now. I already have a new valve cover gasket....maybe that will be my project tomorrow.
     
  16. cdover73

    cdover73 Member

    Yep...same carb! If you dont have the internal problem like I did that required me to buy a new carb (or have yours professionally rebuilt, you have to drill a jet out somewhere and I didnt have the tools or knowledge) then here is my attempt at passing what I learned.

    First, the screw at the top of your pic is for fine air/idle adjustment and I have personally never found it to do much good. Very little response one way or another. 2nd, the screw to the right in your pic is one of the three screws I had luck with. The big one is the warm air/fuel adjustment and the small one next to it on the choke actuator is for cold idle adjust. There is also another one next to your throttle cable attachment that adjusts the very thin spring and gear wheel for the choke. I literally had to screw this one all the way in until it bottomed out then backed off half a turn and left it. Then i unscrewed the small one (on the choke actuator) until it lifted off the base plate (you can see it underneath as you turn the screw). I then screwed it back down until there resistance but no more. THEN, the large screw. This was the most responsive for me. Just get the engine running cold and back it down to a very slightly high idle. Wait til it warms up (it will probably start wanting to die) and screw it in about 1/8th turn at a time until it idles okay. This is your 'sweet spot'. You will have to play aroynd to find the best place to leave it between cild and hot.

    Thus procedure may not be correct in many minds, but is the only thing that worked for me until I bought the new carb. Oh, I run my regulator at 3.5-4 psi now with no problem. Same as i always did. I have been told this is too much but i never had an issue until the carb went out internally. Hope this helps.
     
    Andres Medina and Tyler Y. like this.
  17. Tori Bean

    Tori Bean New Member

    Thank you cdover73!! I turned up my fuel regulator to 2psi and followed your directions for tuning the carb....and I'm happy to say my Hijet is running even better than it was before I started messing with it! The truck is running smoother, and even seems a bit quieter than it was before.
     
  18. cdover73

    cdover73 Member

    Glad I could help. Remember, this isn't the proper technique for adjustment, but it was the only thing that worked for me after hours of adjusting and cussing. I think you may be headed down the same road I did and a new or pro rebuilt carb may be on order. I got away almost two years before I finally broke down and paid the $430 from Yokohama. Now, with the carb set per their instructions (as it should be) and the valves adjusted properly I can start my truck every time, cold or hot, while standing outside. It is SOOOO much more relief than constantly having to work on the dang thing every time I got in it. BTW, a good tune up with new plugs, wires, cap, and rotor will make a bigger difference than you think. And check all your vacuum lines, even if you have already done it. Can't stress enough how sensitive these things are to vacuum leaks. I spray a little WD-40 around the top of the engine where all the hoses are and listen to see if the idle changes. If it surges then I spray that area again in smaller sections until I narrow it down. Just some more pointers. It was hard figuring all this out, but there are many guys on here that helped me along the way that I have mucho appreciation and respect for...
     
  19. Tori Bean

    Tori Bean New Member

    Yes, I haven't even had this truck a year yet, and this site has already saved me a couple times! I actually just recently did all the fluids, sparks, wires, and cleaned the cap n rotor....and yes, it made a great difference! Valve adjustments and looking for vacuum leaks is next on the list, then maybe I can get into some of the fun stuff I want to do like painting and finding a stereo n such.
     
  20. ttc

    ttc Active Member

    I put in a mechless cheap one off bangood for 25 bucks and ran it through the original speaker.. Surprisingly it does t sound bad
     
  21. cdover73

    cdover73 Member

    I put the deckless Clarion in and even though it was cheap I don't recommend it to anybody. It sounds okay and fits in the shallow depth hole of our dash without mods. But the volume knob doesn't work anymore. I have it set to where I want it as far as volume and fade/bal/bass/treble and the only I push is the on/off button! I just hope the battery doesn't run down again and make me have to reset it. That's when I will shop around for a different one.
     

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