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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3977
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Have a Suzuki DT75 1987 that has been having issues few

Customer Question

Have a Suzuki DT75 1987 that has been having issues for a few years. The motor had been rebuilt at a Suzuki dealer years ago by a less informed family member of mine. They did new piston rings, bearings, full workthrough. The engine runs perfect in any type of open throttle. When I attempt to start it I can get her to start by lifting the fast idle lever on it half way and then I'm able to lower the lever. After messing with the carb adjustment screws per the Suzuki manual 1.5 turns out I started getting this Squeak like sound really can't describe it other than that is squeaks like a chirp.
had the boat in the water and was able to keep her easily running for a solid half hour once I had her above idle. When bringing her to a lower speed she chirped once and then stalled on me. Other times I can put it in idle and it will run fine but then just die randomly.
I'm almost thinking a fuel issue but have replaced the fuel bulb, and entire gas tank. I'm not sure if maybe I still have a carb issue or what it is. Last year it was stalling when attempting to go into reverse. This happened once while out on the water this year so far.
Submitted: 2 years ago.
Category: Boat
Expert:  Charles replied 2 years ago.
Hello, my name is***** will be assisting you today.Yes you do still have an issue in the carbs. It sounds like ither one is out of adjustment or the idle passage is still dirty. The setting of 1.5 turns is just a base setting. You will need to do just a bit of fine tuning to get the motor running its best. Have it backed into the water and warm before adjusting on it.
Customer: replied 2 years ago.
Charles,I appreciate your response but do you have access to the actual factory specs on my specific model engine? I figured out I actually had the wrong service manual for a newer dt75 and realized that on my year model the carbs must be Synced using vacuum gauges. I also need to be able to monitor RPM's while doing so. On my engine I still haven't been able to figure out how to hook a tachometer up to it. I have seen Tachometer units on ebay for the DT75 but am not sure if I need one of these or just the actual gauge. Any ideas?
Expert:  Charles replied 2 years ago.
The use of a vacuum gauge is not normally needed on a two stroke engine. The carbs sit directly on the engine block and there is not any where to hook one up,. for a tach, you can get a timing light that has that function built on or a small hand held tach that has a wire that wraps around the number one spark plug lead. Same as on some jet skis.
Customer: replied 2 years ago.
Charles,Please find attached some images from the side of my engine. I have the carbs rebuilt again. Followed the factory spec for setting the air to fuel ratio but am getting a horrible idle now and some engine coughing. I believe the timing is off but I'm having an issue mentally understanding each adjustment to bring the timing down to retardation at idle. Any hints you can give me based on these photos would be great including labeling the actual items your talking about directly on the images.When the engine starts I have to bring the fast idle up which causes the RPMS to shoot up high right after it starts. It then settles down put runs real rough and if I lower the fast idle it dies completely. I'm under the impression that the timing is off because I did at one point have the timing mechanism off without knowing what it was about a year ago before I became a bit more experienced.
Expert:  Charles replied 2 years ago.
on the timing arm leading up to the flywheel, there is a bolt. That is the stop. Tighten that bolt a few turns to lower the timing.
Customer: replied 2 years ago.
Charles wouldn't tightening that bolt cause the timing to advance not lower?
Expert:  Charles replied 2 years ago.
No, with the way that the trigger is set in the engine, moving it forward would lower the timing.
Customer: replied 2 years ago.
Charles,Took the boat out on the lake yesterday to try and get her tuned in. It appears while running at idle around 1,000 rpm with the fast idle up a bit she is showing a timing to the right of the T mark which I assume is top dead center of about 6-7. Lowering the timing any further causes it to stall out. Suzuki seems to be calling for a timing of around 3.. So I was able to go into gear and out of gear but if I hesitated increasing the throttle as I switched into our out of gear the engine would stall from the back pressure of going into gear rpm's would drop to about 500-600 and stall. What linkages do I want to focus on to fine tune the actual idle speed now from the photos I sent you.Think we are just about done here just need to get the final tunes in place.
Expert:  Charles replied 2 years ago.
Try adjusting it on the rod where it attaches to the carb.