40dt suzuki idle inconsistent

[bitsy4643]

Suzuki 1996 40hp idle inconsistent
1996 suzuki dt40 is slow to start, will idle for 3 or more minutes at 800 rpms, then idle will slowly regress until engine stops. If you turn idle adjustment screw before it dies completely back up to 800 rpms, will run at this rpm speed for a few minutes and then begin picking up rpms to around 1200 + . Readjust idle down to 800 rpms, will idle fine for few minutes until slowly regressing or sropping as before. Carb is immaculate, float set correctly, new fuel needle valve and seat , and all new gaskets. Gas is fresh and has sea foam. Any help greatly appreciated
Idle mixture crew at 1 3/4.

[Solarman]

If idle mixture screw is at factory setting, and all pas-sages in carb have been blown out clean with good compressed air, then you might have a problem either with an air leak at a gasket/ seal, or a possible problem with fuel pump? Or other restriction of fuel?

I don't think electrically related, as that wouldn't tend to surge up and down. But not impossible.

Good luck, post back when able to let us know what you find out.

[bitsy4643]

suzuki 40hp 1996 idle inconsistency

New fuel, lines, carb clean with new valve and seat. Same problem. Engine starts at about 1200 rpms. Will run continuously at that rpm, but naturally will not go into gear. Back off start throttle handle, will continuously run at 1000 rpm, back off idle adjustment screw to 900 rpm, engine may run continuously for some time, 2 to 5 minutes, with rpm fluctuating from 700 to 1100 rpm, eventually ,5 to 10 minutes, then motor over a period of 1 to 2 minutes will slowly lose rpms, until stopping. Try to throttle up when engine almost dead, bogs down and will not throttle up. Motor will restart with start handle up and choke engaged and same actions begin as before.

[Solarman]

How long has this been running like this? Did anything happen prior to motor running this way?

Did you remove the #2 (in parts list - carb) air screw when you blewout the air pas-sages? This screw must be removed when cleaned.

What do the plugs look like, and have you checked the cylinders compression?

Post back when able to let us know. Good luck.

[bitsy4643]

Engine continues ti rev up and slow down and eventually stop. Pulled plugs, both wet with fuel, evidently flooding engine at idle speed.

[Solarman]

Ok. That's an indication it is not getting enough air.
This means you did not blow out the air pas-sages as i told you, or the choke is stuck on? As mentioned in previous post the #2 screw must be removed.

Good luck. Let us know what you find out?

[bitsy4643]

Carb completely disassembled originally, #2 screw and carb was immaculate when taken down, but I again used carb cleaner with straw and double checked all passages clear. Same problem upon reassembly. Yes, it is definitely slowly flooding engine until stopping. This may take 1 minute or five minutes. Restart same problem.

[Solarman]

do you have the suzuki manual for your motor?
Does it give a test for the ignition sensor? the ignition sensor is located under the flywheel. also test the rectifier/ regulator assy, to make sure it is receiving/ delivering proper voltages.

when your motor stalls out, do you notice fuel in throat of carb, only after stalling out? possibility of slight leak in float?

Post back when able.

[bitsy4643]

No fuel in throat of carb. Have 1996 suzuki manual. Noticed it mentioned 100/1 mixture on 9 and 15hp engines, and 50/1 on 55 and 65hp. No mention of 40hp mixture. As engine is very slow to start, 5 to 10 seconds, and smokes very excessively on start up and also smokes somewhat at normal running rpm's, would wrong oil mixture effect idling? Thanks

[Solarman]

it can affect running. proper oil mix is very important. too much oil can foul plugs, and cause poor performance. too little oil, that can cause damage. you should be running 50:1 if mixing by hand. the oil injected motors inject 75:1. if your oil injection system is not working stick with 50:1 mix.

Good luck.

[bitsy4643]

Thanks for your help. another related issue, Suzuki clymer shop manual on my identical carb for Suzuki 2-65 hp on page 210 shows float with metal piece float stop mounted toward carb assembly, on page 211 shows float installed just the opposite with metal piece opposite carb assembly and installed toward carb bowl. Which is correct, I assume page 210 correct, but very confusing as manual should be consistent. Thanks

[bitsy4643]

Float?

Carb float 13250-93012 diagram on page 210 of clymer manual and on Suzuki website shows metal piece on float clearly installed toward carb body. 211 of clymer manual show same float mounted with metal mounting toward carb fuel bowl. Float will not install correctly as shown on Suzuki diagram or either metal piece installed on wrong side of float in MFG. Please comment. Thanks

[Solarman]

bitsy, do not repeat posts over and over.
i do not have all the manuals clymer, or suzuki, to comment on them.

The floats in all my different motors carbs can only be installed one way. if installed the wrong way, the bowl will not fit, and proper float adjustment won't work.

Good luck.

[bitsy4643]

Idling inconsistency

The 40dt and 115 have same carb but different main nozell #. Could incorrect nozzle cause inconsistent idling problems? Idle will vary from 400 rpms, to 1500 rpms at same setting and at times slowly decreasing until stopping.:Thanks

[Solarman]

1996, dt40, 2 stroke idling problems

No, the main nozzle does not operate for idle speeds. Only the idle speed air pas-sages, along with mixture adjustment. As you screw the mixture screw in (to close), you are actually closing the air off, causing a richer fuel mixture. Opening the mixture screw increases the air causing a leaner mixture. However, an incorrect idle jet could cause idle problems.

Good luck, post back when able to let us know how it's going.