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Hi there,
I have spent the last 3-4 years battling a 85' DT85. A couple weeks ago, I had finally gotten it running like a dream. I fixed and replaced a laundry list of things in the past year working on it. I took it out, it finally idled perfectly, and WOT was great. 2 miles later it seized at around 2500 RPM, shaft was obviously stuck, and had to get towed home by a friend. Turned out that the lower unit had a serious water intrusion and the gearbox seized.
Luckily found a used lower unit that fit the motor online, replaced the old one, everything fit perfectly. Go to start it, won't start the first time, try again, get a loud backfire. And now it won't start again.
It was running perfectly before the lower unit freeze, and now won't start. I have checked the obvious things. There is strong spark on all three cylinders with a gap tester, used a testing light to check if the plugs are conducting. Checked the spark order. There is definitely fuel flowing. Checked compression. 125+ on all three cylinders.
The only thing I can find left online is timing. I have the manual, and it discusses static timing, which I easily checked when throttle advanced, the line on the timer matched the upper seal housing line. The only other thing I see is dynamic timing. This requires the motor to be idling, so I'm not sure what I can do with that.
Does anyone know what a seized shaft at 2500 RPM could change to cause a motor to not start. Again I have Spark, Compression, and Fuel. Is there something I'm missing with timing? Any help would be appreciated. This motor has so much potential, I was so excited by its performance before it seized. I am now about ready to drop it in the river.
I have spent the last 3-4 years battling a 85' DT85. A couple weeks ago, I had finally gotten it running like a dream. I fixed and replaced a laundry list of things in the past year working on it. I took it out, it finally idled perfectly, and WOT was great. 2 miles later it seized at around 2500 RPM, shaft was obviously stuck, and had to get towed home by a friend. Turned out that the lower unit had a serious water intrusion and the gearbox seized.
Luckily found a used lower unit that fit the motor online, replaced the old one, everything fit perfectly. Go to start it, won't start the first time, try again, get a loud backfire. And now it won't start again.
It was running perfectly before the lower unit freeze, and now won't start. I have checked the obvious things. There is strong spark on all three cylinders with a gap tester, used a testing light to check if the plugs are conducting. Checked the spark order. There is definitely fuel flowing. Checked compression. 125+ on all three cylinders.
The only thing I can find left online is timing. I have the manual, and it discusses static timing, which I easily checked when throttle advanced, the line on the timer matched the upper seal housing line. The only other thing I see is dynamic timing. This requires the motor to be idling, so I'm not sure what I can do with that.
Does anyone know what a seized shaft at 2500 RPM could change to cause a motor to not start. Again I have Spark, Compression, and Fuel. Is there something I'm missing with timing? Any help would be appreciated. This motor has so much potential, I was so excited by its performance before it seized. I am now about ready to drop it in the river.
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