Suzuki dt2 outboard

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davidivorwynphillips

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My Suzuki dt 2 (about 1995 vintage) has two adjustment screws in the carburetter. One is the idle speed, the other a pilot air adjustment. Not sure how to set these up correctly as there is little information in the suzuki manual. Anyone still using these and in the know?
 
Two strokes are normally easy to set if all the carb jets are clean and the float height is correct. Remember that screwing the air bleed screw in richens the mixture by closing off the air and it is better to err on the slightly rich rather than the slightly lean.

Does the engine idle at the moment? If not then gently screw in the air bleed until it is fully home and see how many turns out it is currently. If it's between 2 and 3 complete turns then the engine should start and you just need to screw in the idle speed to get it to idle. You can then start fine tuning the air bleed a 1/4 turn each way to see if the revs increase and you can back off the idle a tad. Aim for the fastest stable/smooth revs and then turn the air bleed in 1/4 turn just to richen up.

If the air screw is more or less than 2 - 3 turns out, set it to 2.5 turns and try to start again. If you can't catch it on the throttle at this setting and get at least a burst of revs (a quick squirt of 2T fuel mix directly into the inlet should give it a quick boost) then there is something else wrong ..... usually a dirty carb, float height or electrics.

Richard
 
The air screw works by raising the piston in the carburetter. So screwing it in causes an increase in revs, screwing it out and therefore dropping the piston reduces the revs. The problem is that the direction of the manual to screw it in fully and then out 1-2 turns means that the piston is far too high and the engine races in the idle position. I've fiddled around with both the idle adjustment and air screw and got it idling at a reasonable speed but would like to know how these are optimally adjusted (if there be such a thing)
 
davidivorwynphillips said:
The air screw works by raising the piston in the carburetter. So screwing it in causes an increase in revs, screwing it out and therefore dropping the piston reduces the revs. The problem is that the direction of the manual to screw it in fully and then out 1-2 turns means that the piston is far too high and the engine races in the idle position. I've fiddled around with both the idle adjustment and air screw and got it idling at a reasonable speed but would like to know how these are optimally adjusted (if there be such a thing)
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That's odd. If screwing it in always increases the revs and screwing it out always reduces the revs that's not like any pilot air bleed screw that I've ever adjusted. It sounds like a throttle stop / idle speed adjustment. Are you sure that there's not another screw with a tapered end which controls the air bleed at idle and should have a "sweet spot" which moving away from in either direction causes the engine to go slower? On modern engines this air bleed if often blanked off but that's not usually the case with older engines.

I'll see if I can find the manual online and take a look.

Sorry for the confusion.

Richard

This image http://www.brownspoint.com/store/pc/suzuki/images/dt2/05/fig005.jpg shows the adjustment two screws side by side. If screwing the air bleed screw doesn't affect the revs as expected I wonder if the float height is incorrect. Have you checked this?
 
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Thanks for your help.
It's a tapered screw which when screwed in raises the carb piston and therefore acts as an idle adjustment. However there is a second tapered screw which controls the idle fuel flow. just wondering how these two should tango.

Although the Brown's point diagram seems to show them side by side they do very different things. Thinks float height is right but will check.

D.
 
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It would be on the idle screw but shouldn't on the mixture screw. If it is Sir you clearly have problems ;)

To set the idle I will always screw the idle screw out until the slide is at the bottom and then screw it back in till the slide lifts about 1mm, it should start and idle high then it's just a case of backing it off till you get the required tickover.

Once you're on the required tickover you can adjust the mixture by screwing the mixture screw in until the revs drop and then 1/4 of a turn back but this is very subtle and mostly a mixture screw on a small twostroke can be screwed right the way in and back out without noticing a difference.

If you can't get it to idle I would look at replacing the pilot jet, or even better getting the carb ultrasonically cleaned and rebuilt with new items.
 
davidivorwynphillips said:
Thanks for your help.
It's a tapered screw which when screwed in raises the carb piston and therefore acts as an idle adjustment. However there is a second tapered screw which controls the idle fuel flow. just wondering how these two should tango.

Although the Brown's point diagram seems to show them side by side they do very different things. Thinks float height is right but will check.

D.
Click to expand...

OK .... I think we're getting there. What you're calling the idle fuel flow screw is the idle air bleed screw. It's controlling the amount of air passing through the idle jet so the further you screw it in, the less air and the richer the mixture.

The screw which you are trying to turn 1.5 - 2 turns out is the idle speed adjustment so the 1.5 - 2 turns is not relevant to the that screw.

You therefore need to try the procedure I outlined in post #2 but using the screw 24 in the diagram above. Screw out the throttle stop screw number 22 to get the engine idling as slowly as possible as it will then be more sensitive to the adjustment of screw 24. Don't forget to check how many turns out screw 24 is at the moment and start from that point, by going in and then out 1/2 turn to see if you can increase the revs.

Richard
 
davidivorwynphillips said:
OK - I think some of the problem is the description in the manual. But will try this!

Many thanks!
Click to expand...

Screw the pilot air screw (# 24) in until gently seated and then back out by 2 turns ........ 2 turns is the correct initial setting but it should not be overly critical

Close the choke, part open the throttle and you should be able to start the engine. It may start on a fairly small throttle opening or it may need to be nearly fully open ... whichever.
As it warms up progressively open the choke again and reduce the speed with the throttle lever.

When warmed up progressively close the throttle control and adjust the throttle stop / idle speed screw (#22) until you have it running at a normal idle speed (800 - 900 rpm IIRC)

Now to tweak the pilot air adjustment reduce the idle speed to be as slow as possible and tweak the screw a small fraction of a turn at a time until running at its best.

Finally reset the throttle stop (#22) to give a "normal" idle speed
 
VicS said:
Screw the pilot air screw (# 24) in until gently seated and then back out by 2 turns ........ 2 turns is the correct initial setting but it should not be overly critical

Close the choke, part open the throttle and you should be able to start the engine. It may start on a fairly small throttle opening or it may need to be nearly fully open ... whichever.
As it warms up progressively open the choke again and reduce the speed with the throttle lever.

When warmed up progressively close the throttle control and adjust the throttle stop / idle speed screw (#22) until you have it running at a normal idle speed (800 - 900 rpm IIRC)

Now to tweak the pilot air adjustment reduce the idle speed to be as slow as possible and tweak the screw a small fraction of a turn at a time until running at its best.

Finally reset the throttle stop (#22) to give a "normal" idle speed
Click to expand...

Isn't that exactly what I said in #2 and #10? :confused:

Richard
 
Ok thanks everyone. The air screw has relatively little effect on the revs even with very slow running until one is within half a turn or so to complete closure. So I have left it at the manual recommendation of 13/4 turns out where it seems to run well.
 
davidivorwynphillips said:
Ok thanks everyone. The air screw has relatively little effect on the revs even with very slow running until one is within half a turn or so to complete closure. So I have left it at the manual recommendation of 13/4 turns out where it seems to run well.
Click to expand...

Have you tried going out further than 1 3/4? If going out starts to slow down the slow idle then screw back in until the revs pick up again. However, it sounds like 1 3/4 might be about right.

Richard
 
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