surging dt85

[jakdan3]

I have an 88 dt85 that surges when running on the water at any speed. It seems like it all of a sudden gets a big burst of speed then seems loaded up. I rebuilt carbs because it wouldn't go more than five mph and would stall constantly. Bottom carb float valve was stuck. Runs way better now but surges like crazy and still stalls. I've got fuel pump apart now, looks good.

[Solarman]

dt85, surging

Check the small clear plastic discs in base (check valves). Are they intact, or fractured? They are not part of a rebuild kit, if they are damaged a new pump is only way to get them. It sounds like the floats may not be letting enough gas into the bowls, did you adjust float levels, are you sure you cleaned the jets completely? Did you soak the carbs??
Let us know.

[Wagoneer]

Surging means it's running lean, so start troubleshooting everything fuel related. It may just be as simple as adjusting the high speed screw on the carb (if it has one).

[jakdan3]

The clear discs look good. I did not soak carbs I gave it the quick spray job, I did not adjust floats either. Maybe I'll soak the carbs and see if that helps. I put new plugs in and ran it yesterday, I'll try and post a pic later to see if that helps.

[Solarman]

dt85, surging

OK. Soak carbs and make sure you remove the high speed jets, middle of float chamber, and low speed jets, front, or side of carb body, and needle valves with the seats. Then before assy use air to blow through all the holes/ passages. Then make sure floats are adjusted properly when re-assembled.
Count the turns of the low speed jets for each carb till lightly seated closed. This way you can put them back just as they were.
Let us know after done and how it runs.

[jakdan3]

I will do that. Where should the low speed jets be initially set? The bottom carb was turned out five full turns when I rebuilt them before. I think the guy I bought the boat from was messing with stuff before. I want to say I put them one and a half turns out.

[jakdan3]

here is a pic of the plugs after 30 minutes of running

[jakdan3]

also can anyone tell me what and if this sensor is installed correctly? seems wrong to me and I can't find it anywhere on the parts lists.

[Solarman]

plugs, and sensor pics

The plugs look good, but hard to tell how the motor is running, plus if it is surging it could be rich and lean.
The sensor appears to be your water temp sensor, or overheat sensor. Yes, it looks to be installed wrong. I can only see partial pics here, but it looks like it's on the exhaust water jacket cover plate. If it is the proper sensor, then the rubber grommet should be under the clamp on top of the spring and sealing the sensor in the hole. Just to keep it from rusting inside of the hole.
You should get a Suzuki shop manual.
Keep us posted on how you're doing.

[jakdan3]

here are some better pictures of that sensor. I am thinking this isn't the right sensor. I believe the proper sensor is supposed to go in the empty hole on the head. If I am not mistaken the only thing this sensor does is sounds the alarm as it is hooked up directly to it. I don't know if this would cause a limp home situation. I have the carbs rebuilt and am going to test later today. I will let you know how things go. Oh, the floats on number one and two were adjusted close to where they should be but number three was WAY off it would have shut fuel off with the bowl only half full or less.

[Solarman]

dt85, surging issues

Not sure about sensor, maybe they replaced it with different style if they couldn't find right one, or if they stripped threads that secure it? If it ran, it may still work?
I was thinking the float might have been the cause if needle valve was sticking shut, but low float level may cause the same thing.
Good luck and keep us posted.

[jakdan3]

OK, I have got it all back together. It is running way better. No more surge. But I think I have to adjust the mixture screws yet. It runs good at wide open although I think it should be going way faster than it is. Can only manage 23 mph. And if I try and go 1/4 to 1/2 throttle it stalls. Looking at the plugs after running for 45 minutes they look like its running lean. My question is do I have to turn the mixture screws in or out? I'm used to turning the screw out to richen it but the plastic cover over the carbs shows the opposite. Is the Suzuki different or am mistaken?

[Solarman]

dt85, running issues

The mixture screw is only for idle. Why is called the idle mixture screw.
All of your carbs idle screws should be set almost identical, fractional differences can occur because jet and seat are not identical (perfectly the same).
Manual should say what to set them at.
The mixture screw adjusts the amount of air let in to mix with the predetermined amount of fuel.
So in answer to your question, clockwise is richer (less air in), and counterclockwise is leaner (more air in).
Set them and let us know, there may be other issues you are having.