1985 DT75 won't idle.

[markdtn]

We bought this motor new in 1986. It was put on a 1973 Glastron tri-hull. Ran regularly and well. Over the years very trouble free. Rebuilt the starter once, replaced the water pump and foot oil a few times, plugs yearly, and went through the carbs a few times. In about 2000 it got stored in a barn. In 2017 I pulled it out and built the carbs, replaced the plugs water pump and thermostat, and rebuilt the fuel pump (all real Suzuki parts except offbrand carb kits and NGK plugs). Couldn't get it to idle and the electric choke is weak-you have to manually choke it. I wanted to sell it on the junk Glastron (really rotten floors) but it didn't run right so I didn't try too hard. This year my parents got a newer pontoon boat and reused the engine they had, so I got a 1984 24' PartiCraft. Put the DT75 on it and now I want to sell the package. But it won't idle. Last Saturday I pulled the carbs and cleaned them with an ultrasonic cleaner. I had previously set the idle air screws 1 1/2 turns out so I started there. Put the boat in the water and still the same problem. I started richening them (clockwise according to the air cleaner cover) so I am now about 3/4 turns in from where I started. Even warm you have to choke it manually for it to start. I didn't recheck compression, but it was good 2 years ago. I have been running ethanol free fuel with some oil in it so I know it is getting oil. It sounds good when it runs, but it just won't idle. Any thoughts on where to start? Thank you!

[Solarman]

It sounds like the idle air fuel mixture pas-sages are still blocked, did you blow them out with compressed air? You should set the idle air-mix screws, all carbs should be set identically per the manual.

Check and lube electric coke butterflies, they should be free to move.

Good luck, post back on what you find.

[markdtn]

I did blow the passages out with air after ultrasonic cleaning. And honestly they were pretty clean from the manual cleaning 2 years ago since there was no time on the engine since. The choke butterflies do move nicely on each carb, but the electric solenoid does not seem strong enough to pull them in. I am going to check connections and grounds on that.

Unfortunately I don't have a shop manual. I did find one online for a 1988 DT75 that says the initial setting for idle screws is 1.5-2.25 turns. Maybe I just have not gone far enough yet? Having to choke it even warm tells me I am maybe still too lean?

And just to be sure. The idle air screws go clockwise (in) to richen? Seems counter-intuitive, but that is what the cover says.

[Solarman]

Yes, the mixture screws go in to make mixture richer, they are adjusting the amount of air mixing with fuel. Fuel is constant amount set at factory. This is why all carbs are set identically. I might start at 1 full turn. Then run the motor idling as much as able, and read the color of the plugs after a few weeks. If color is too dark open to 1-1/4, and if color is still too white, go to 3/4.
As far as hard starting, clean the plunger that goes into the choke windings, if it is free then you may have to replace the choke coil part. If the shaft and butterflies are all free to move, the windings of the coil must be shorted, not pulling the plunger in to choke well.

It is not uncommon on the earlier motors to need to choke them on the initial start after pumping bulb up. Also, occasionally when motor is heated up. But most of the time once warmed up it starts up without choking, provided all adjustments are set up like the factory.

If you have changed anything, then all should be put back to factory settings.

Otherwise, hard starting may/usually indicates you are not getting initial fuel (choke is one reason, restrictions of small/tiny holes/pas-sages in throat of carb another - most likely), then we look at possibilities of electrical problems (gear counting coil (adjustment & resistance), then possibly the throttle sensor, or heat sensors reading motor too warm? Exactly how your motor sounds and runs, as well as what preceded the problems usually can help solve what is wrong.
Initially, it appears the long duration sitting up is the best answer to why it runs as it does.

Sorry I can't tell you specifically what is wrong. Being on this side of the computer has its limitations, but details on what you find can identify what is happening/breaking down.

Anytime cleaning carbs, always record any adjustable screws settings if they need to be removed. Most linkages do not need to be removed if cleaning, only those parts related to fuel AND air flow. I generally soak my carbs, but make sure every jet & hole is clean, every air pas-sage is clean. Remember each tiny hole in every jet/ carb has a reason. Every piece of trash in carbs comes from somewhere, identifying the trash can tell you if your hoses are breaking down, or diaphrams in fuel pumps. Remember too, large trash doesn't get past/by many filters, so where from?

I do tend to get carried away in thoughts.

Good luck, post back on what you find out.

[markdtn]

OK. Thank you! I am pretty confident that the carbs are clean and all the passages are also. When I cleaned them 2 years ago I cleaned each passage with solvent, a torch tip cleaner, and compressed air. Then a few months ago I bought an ultrasonic cleaner so 2 Saturdays ago I tore them down again and did them 30 minutes each, then blew them out with air. They really just had oil residue in the bowls. Needle and seat all sealed against me blowing in the inlet and raising the float when I was done. When I primed it with the bulb it had a nice hard resistance after the system filled up. Neither time tearing down the carbs did I really have any large trash inside. I rebuilt the fuel pump as a precaution and since it sat so long.

I did forget 2 years ago to remember the idle screw setting when I tore them down. That was my fault. I will start with 1 turn this time and see where it goes. When it starts at high idle it sounds like it always has, just running fast. You can get it to about half high idle and it will stay there. When you go to zero it runs slower and slower and stops, it takes a few seconds. It always needed choke to start cold, but never when warm.

We have had this motor since it was new, so I know the history of it well. My parents claim it was my HS graduation present, even though it was their boat. I cut a tendon in a finger while installing it and to this day that finger won't fully straighten. (Finger in wrong place while picking up the crate with a forklift). It has been an excellent power plant and has served us well. Lots of good memories with this motor. It replaced a 65 Johnson that was 10 years old, threw a rod, fixed with JB weld, and then threw a rod in another cylinder 2 years later. At that time Suzuki had figured it out much better than the US guys and they were everywhere. OIl injection, no more mixing fuel, better mileage than the Johnson, and it ran like a champ!. I have no complaints with it at all. I know I am so close to figuring this out. I think it is trying to punish me for selling it, but you can't keep everything.

Hopefully this Saturday I can get it back in the water and play with it some more. I'll let you know how it goes.

[markdtn]

Took it to the lake Saturday. I started with the idle screws 3/4 out. That did much better. I ended up with them in another 1/8 and I may go just a touch more. It still does not like the idle time from dock to the edge of the no-wake-zone and back but it was vastly improved and is now drivable. It dies, but will start right back up without choke.

On the choke I tested it with live power and it would not pull them closed. So I removed the linkage (they are all nice and free without linkage) and I started out with it just pulling the center carb. No problem. Then the bottom and center, no problem. When I add the 3rd it just wont do it. So I removed the return spring on the top carb from it' stop and it will pull all 3. Now it relies on airflow to open them. Not the best solution, but it worked. Now I can market the boat. Thanks for all the good advice.

[Solarman]

Also, start running fuel additive in each tank of fuel, especially if running ethanol fuels, it might help as you run it more and more.

Good luck, post back if still having problems.

[Solarman]

Also, the idle stop screw is different than the idle air mixture screws, but make sure you do not run the motor too lean? Plugs will be white and dry, even look like they have gotten too hot. A slight chocolate tan is a good color.

Running the fuel cleaner may find something that didn't get totally clean.

Good luck.