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93 Carry DD51T Carb Tuning

Discussion in 'Suzuki Carry' started by Cole, Aug 6, 2017.

  1. Cole

    Cole Member

    Hello. I posted this also in the "desperately need tuning help" thread but I thought maybe it should also be stand alone for easy access. I am new at the whole Forum thing so......

    Okay here we go. I just want to say that the following information is just what I have gathered from other peoples threads (main Spanner! lol). I am not trying to take credit for other peoples work. I am hoping to just compile everything I have been reading over the last couple months. All pictures but one are of my own Carb and I have attached numbers to the screws, which I believe match up with descriptions and missing photos previously in the thread.

    As mentioned may times, in multiple threads, CARB tuning will only be easy/helpful if you have no vacuum leaks, correct routing and everything else correct. You can't tune a CARB to fix other problems!
    Also I am going to assume that your Choke is set up to begin with. You can find a lot of good information in the thread "Choke-idle is too high". There is no sense repeating that. However I will identify the screws.

    Carburetor adjustment screws

    Screw #1 - Idle-up Actuator Adjustment (This is for starting/restarting purposes. It holds the throttle above base idle. Like putting your foot on the pedal when starting the engine. As soon as the engine starts the actuator should retract and remove itself from the system until the engine stops.)

    Screw #2 - Accessory Idle Adjustment (This increases the engine RPM for when there is extra load on the engine aka Blower motor, Headlights, Rad Fan, Hydraulic Dump, etc. There is a control relay that operates a solenoid valve and uses Vacuum directly from the intake manifold to operate the actuator when the previous items are in use. Otherwise it is out of the picture on standby)

    Screw #3 - Base Idle (Rather simple. It adjusts the throttle to maintain the engines base idle approx 950 RPM)

    Screw #4 - Choke plate adjustment ( I borrowed this picture. It is directly above the thermal pusher pin on the side of the CARB. It adjusts the Choke plate position and thermal pusher pin is responsible for removing the Choke when the engine warms up)

    Screw #5 - Choke Idle (Again rather simple. This screw adjusts the RPM the engine will run at when the engine is in it's warming up phase. From what I have read approx 2000-2500 RPM. It allows the engine to warm up faster.)

    Screw # 6 - CO2 Fine Adjustment (Some call this the CO2 Fine adjustment as the manual describes adjusting is with a CO2 monitor in the tail pipe. Some call it the Fuel/Air mixture screw. Either way my understanding is that it doesn't accomplish much and I have yet to play with mine.)

    Carburetor Adjustment

    With engine cold the Choke plate should be 100% closed (adjusted by screw #4)

    Start the engine and the Choke plate should open to 85% via the Choke actuator. The Idle-up actuator should also retract. The engine is now warming up and the Choke RPM can be adjusted using Screw #5.

    At this point Screws #1,2,3 should be off their seats.

    Allow the engine to completely WARM up and the choke to remove its self from the system. Check that the other screws are still off their seats. If not make sure the actuators are in the proper position and back them off. Now the engine in running using Screw #3 base idle. If staring from scratch you may need to hold the throttle, up to this point, to keep engine running as base idle had not been set. If you are working from a Carb already in use then you adjust this screw to obtain the Base RPM of Approx 950 RPM (Without any lights, Rad fan, blower motor, etc on). I don't have a TACH yet so I use a portable hand held one pushed against the crankshaft. Shut off the engine and restart and confirm the engine is at base idle.

    The engine has now warmed up in the Choke phase and is running at it's base idle.

    Now to adjust the idle-up actuator. Adjust the screw #1 so that it is almost in contact with the seat. When the engine is turned off it will contact the seat and throttle up the engine. This is responsible for the momentary higher RPM when you initially start a previously warmed up engine. I found I needed to make a couple small adjustments to this after cycling the engine a couple times to find the sweet spot. I do not have an actual number for this but it would be around 1500-2000 RPM give or take.

    Finally we come to the Accessory Idle adjustment screw #2. With the engine running and warmed up and the previous steps complete make sure no accessories are on, the actuator is not retracted and engine is at base idle. Now turn you lights or blower motor on full and the actuator should retract to open the throttle. Now adjust screw #2 toward the seat and keep adjusting until you start to raise the engine RPM. This should be set at approx 1500 RPM. Now turn all the loads off and the RPM should drop to base idle. Turn them back on and RPM should increase.

    Congrats! Your Carb should function as is should.

    I also found a lot of good info in the thread - 93suzuki Carburetor (carefull there are two)

    Hopefully this clears it up for some of you. I felt it was my time to help after months of lurking and reading!lol I am not an expert just very obsessive in the stuff i am interested in.

    Attached Files:

    RuggedCraig likes this.
  2. fmartin_gila

    fmartin_gila Active Member

    Looks like you have done a lot of 'homework'. Should be welcomed by many as there seems to be a constant need for this type info.

  3. KCCats

    KCCats Member

    This is great!
    Now we should put the Vac diagram with this!
  4. Cole

    Cole Member

    Did you have any particular diagrams in mind?
  5. KCCats

    KCCats Member

    The vacuum lines from where on carb to where they go?
    Last edited: Aug 21, 2017
  6. rugerman

    rugerman Bronze Supporting Member

    Phenomenal info there Cole. GOing through the process of tracking all of these on mine. What I have found is that after it was rebuilt at G and R they apparently backed all of these screws out so that they could be set y the truck owner. Or....they didn't. Either way all of mine are adjusted out, and not working correctly but seem to be actuating.
  7. Cole

    Cole Member

    Thanks. It's not so much my info as other people's. I just tried to do some compiling. Let me know if you have any questions!
  8. KCCats

    KCCats Member

    Is there a way we could link or post the Vacum lines so this could be a complete How To!
  9. Cole

    Cole Member

    I'll try to put something together from what I have found. It may take a bit. I am just getting started on all my upgrades. Do you have any info yourself?
  10. KCCats

    KCCats Member

    No and I still need to send my carb off to be rebuilt!
  11. rugerman

    rugerman Bronze Supporting Member


    Couple questions here.

    #1-What did you use to adjust your ide up screw. finally got a look at it and it appears to be a tamper proof hex head? Looks like it in your picture also. Hardly any room in there for anything to adjust the screw.

    #2-Where is that fine Co2 screw at. Thought I knew my carry like the back of my hand yet I do not recognize that area.

    #3- Could you explain the thermal pusher pin. I look under that adjustment screw and I see a shiny pin that is protruding up at an angle from the housing where the carb coolant lines run in and out of. How does this work exactly. When I fire up my truck the high idle does not activate and I am wondering if I am out of adjustment with one of these choke adjustments here. I see that the choke speed adjustment screw seems to be screwed all the way in when I manually move the throttle linkage and peek behind there but not exactly sure what I should be adjusted to. Should probably know that before I tinker.
  12. KCCats

    KCCats Member

    My idle screw is a Philips and a stubby is what I used to raise my idle!
    The rest I have no idea?
  13. Cole

    Cole Member

    Okay. Good questions. I am by no means an expert but I'll take a crack at it. #1 my idle-up screw is a Philips like KCCATS. I think it is #1 or # 2 Philips screw. I use a stubby bit held in a extension. It is only about 2" long and very narrow so it fits pretty good.

    #2 The CO2 screw is located between where the VAC lines come off the CARB. Either the 3+2 or 2+ 3 setup. It is centred on the carb and closest to the intake manifold. Now this one is very hard to get at!!

    #3 I haven't actually had the thermal pusher apart so I can only assume that it is similar to your typical engine thermostat. There would be a piece of wax located inside and when the engine coolant heats up it expands and pushes the pin out the top. Likewise as it cools it retracts. This allows the carb to apply the appropriate amount of choke depending on the engine temperature. I here some say those lines can become clogged and that can cause the pin to not move at the correct rate (too slow if at all) which leads to the choke not coming off. You can watch this if you remove the intake boot from the air box and start the engine from cold and just observe the choke plate.

    So the screw just above the pusher pin on the choke assembly should be adjusted when cold to just contact the pin. This is there to take the "play" out of the system. And that hard to see one in the back is your choke idle. I will take a look on mine and get back to you on the setting. I can't quite think about it without seeing it. Hope this answers some of the questions.

    Also when you say fire up and high idle doesn't activate do you mean the idle-up actuator or just the choke idle at approx 2000 rpm?
  14. KCCats

    KCCats Member

    I understand that the vac lines them self are 3mm or 1/8" but how many feet are needed to replace them al?
  15. Cole

    Cole Member

    I have most of mine replaced I bought 25' of the 3mm. Works good but probably not enough. I would have to say you would need probably 35-40' to be on the safe side.
  16. KCCats

    KCCats Member

    OK basically what are the differences between the DD51 and my DB51?
    Mine is 4x4 and do you really think it will take 35-40' of hose?
  17. KCCats

    KCCats Member

  18. Cole

    Cole Member

    Ya that looks like the stuff. I am not exactly sure what the differences between those two are. From what I can tell it is just a change in body style from one generation to another. As far as that length goes you would be surprised how quickly you will use it up. That's just an estimate on length. There are a lot of lines on these trucks.
  19. KCCats

    KCCats Member

    So what is different from aDD51 and aDB51?
  20. Cole

    Cole Member

    Just a change in body style from what I can tell

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