85hp suzuki cuts back to 1/2 throttle

[Gregg Lutz]

I have 1987 suzuki dt85 2stroke motor runs wot for about 600yds then cuts back to1/2 throttle and slows down no wake speed pump bulb and hit choke does not change rpms shut off and start right back it will go to plane for a shorter time,wait 10 min it goes just like cold.There is no alarms no lights.compression is 120-130 pulled air box watching fuel spray looks like it is not running out.water coming out of motor is not hot

 

[James R]

Re: 85hp suzuki cuts back to 1/2 throttle

The alarm could be defective. Throttling back by the motor is usually the result of an oiling problem. If it is an oiling problem you should run on 50:1 for safety until the cause is known. Try disconnecting the tank level switch connector and try the motor. If that does not do it then try disconnecting the oil flow switch connector and try again. These oiling systems rarely fail. Could be bad oil, a blockage, or air trapped in the pump system.
Some of the models have water flow and temperature sensors. Again, these can be disconnected to check each for failure.

 

[Gregg Lutz]

Re: 85hp suzuki cuts back to 1/2 throttle

Hi James,
Thanks for responding. Checked alarm, alarm is good. Checked float level on oil tank by lifting float and problem still happens. Oil lights showing full of oil and tank is full. I am going to check to see if oil is pumping. Do you have any suggestions on how to check if the oil is flowing? 1987 does not have water flow sensor only temperature sensor. Pulled thermostat and tested, it is opening properly. Already mixed oil in gas. If you have any other suggestions feel free to throw them out. Not having much luck.

Thanks again,
Gregg

 

[James R]

Re: 85hp suzuki cuts back to 1/2 throttle

Did you disconnect the pump flow sensor and try that to kill the warning buzzer.
Checking the oil flow is not too difficult. A manual will give the flow specs for your motor. Use a 50:1 mix whilst testing.
You will need to remove the oil tank.
I use a graduated in milli liters siringe. Hang the siringe above the pump and connect to the pump intake with a suitable piece of clear plastic tube. I fill the siringe and tube with the oil first to minimize air in the system. Disconnect the pump mechanical link from the carb.
Your specs will tell you to run the motor at a particular RPM for a specific time with the pump fully closed, record the amount of oil passed shown by the level in the siringe. Do the same with the pump held fully open.
This will tell you the condition of the oil flow.
Remove each oil line at the intake manifold. With the motor running observe that oil is oozing from each line.
If satisfied put it all back together.
If not satisfied it could just be air trapped in the pump. You will need to open the bleed screw whith the motor running to push the air out and then try the test again.
These oiling systems are extremely reliable.
Incidentally, if the oil has been sitting in the tank without use for a couple of years it could have congealed.
I run Penzoil Synthetic Blend 2 Stroke in all my motors and all seems to be well. Get less smoke as well.
Hope this helps.

 

[Gregg Lutz]

Re: 85hp suzuki cuts back to 1/2 throttle

Thanks again will give it shot this weekend

 

[Gregg Lutz]

Re: 85hp suzuki cuts back to 1/2 throttle

Hi James
Well this weekend turned out to be 3 weeks problem still there will run all day 3/4 throttle mainly use for local fishin dont need to go fast just going to keep searching for the problem thanks for your help
Gregg