I have an early 80's 3.5HP single cylinder two stroke Suzuki with a persistent, recurring carburetor problem. In this forum I learned that many others had same problem. I have solved the carb problem. The Suzuki parts and repair manual do not have a complete parts diagram of the DT3.5 carburetor. Thus it was difficult to properly inspect and clean the carb. The common problem is that these motors will not run at low speed-idle speed. As others have surmised, it is because the low speed fuel circuit is not functioning. Without a proper carb component diagram, it is difficult to remedy.
I examined my carb and found a slotted brass screw facing upright, on the right side of the carb body. I removed that and saw a tiny brass "jet" beneath it. This is the "low speed" fuel supply jet. It is not identified on the official parts diagram nor is it discussed in the repair manual. That jet is not removable, it is permanently pressed into place when the carb was constructed. The orifice of this jet is very small. A sewing needle is small enough to push into the orifice. After removing the bowel & float & and bowel gasket, I soaked the carb in a gallon can of Carburetor cleaner. After, I sprayed the carb with common brake cleaner which quickly evaporates. The Low speed jet was clean and open. The two tiny passages in the carb barrel that deliver the low speed fuel supply alongside the Throttle plate were also open & clear.
I reassembled the carb, and the motor started instantly and ran perfectly at low idle speed.
To prevent further corrosion & blockage of these tiny jets & orifices, do not use alcohol gasoline, use only pure gasoline. The Octane rating is irrelevant. I now have a reliable trolling motor and I know how to fix it if the problem occurs again. I hope this helps others who may search for help as I did on this website.
I examined my carb and found a slotted brass screw facing upright, on the right side of the carb body. I removed that and saw a tiny brass "jet" beneath it. This is the "low speed" fuel supply jet. It is not identified on the official parts diagram nor is it discussed in the repair manual. That jet is not removable, it is permanently pressed into place when the carb was constructed. The orifice of this jet is very small. A sewing needle is small enough to push into the orifice. After removing the bowel & float & and bowel gasket, I soaked the carb in a gallon can of Carburetor cleaner. After, I sprayed the carb with common brake cleaner which quickly evaporates. The Low speed jet was clean and open. The two tiny passages in the carb barrel that deliver the low speed fuel supply alongside the Throttle plate were also open & clear.
I reassembled the carb, and the motor started instantly and ran perfectly at low idle speed.
To prevent further corrosion & blockage of these tiny jets & orifices, do not use alcohol gasoline, use only pure gasoline. The Octane rating is irrelevant. I now have a reliable trolling motor and I know how to fix it if the problem occurs again. I hope this helps others who may search for help as I did on this website.