318 Onan OVERSPEED.

[kketterer]

Hi guys,

I have a deere 318, with the ONAN motor. I have been having an odd problem. The machine starts and idles perfectly, runs to WOT perfectly. However after several minutes of mowing, the engine begins to overspeed. I am able to bring the speed down with the throttle lever, however it's still too high.It will not "fix itself" until the engine cools down. It sounds like a very lean condition.
The carb has been flushed and cleaned. The fuel filter had been replaced.
What next? All intake gaskets, fuel Pump, fuel tank vent, Fuel Lines?

Any suggestions?

 

[scrappy isb67]

Hi guys,

I have a deere 318, with the ONAN motor. I have been having an odd problem. The machine starts and idles perfectly, runs to WOT perfectly. However after several minutes of mowing, the engine begins to overspeed. I am able to bring the speed down with the throttle lever, however it's still too high.It will not "fix itself" until the engine cools down. It sounds like a very lean condition.
The carb has been flushed and cleaned. The fuel filter had been replaced.
What next? All intake gaskets, fuel Pump, fuel tank vent, Fuel Lines?

Any suggestions?

it sounds like the the governor is sticking.

 

[glc24]

it sounds like the the governor is sticking.

+1:thumbsup:
The flyball spacer may have broken,or the cup and race on the camshaft may have excessive wear.


Greg

 

[kketterer]

+1:thumbsup:
The flyball spacer may have broken,or the cup and race on the camshaft may have excessive wear.


Greg

So it guess I should pull the motor and split the case to inspect that?

 

[glc24]

kketterer,Welcome To TBN
There is no splitting the case,but you would have to take the fan shroud off,then the flywheel,then the governor housing cover,in order to inspect the governor. I would exhaust all other options before having to disassemble the engine though.

Greg

 

[kketterer]

kketterer,Welcome To TBN
There is no splitting the case,but you would have to take the fan shroud off,then the flywheel,then the governor housing cover,in order to inspect the governor. I would exhaust all other options before having to disassemble the engine though.

Greg

So I guess I would be looking for "other options" then.. Any suggestions?

 

[glc24]

There are some very knowledgable people over at weekend freedom machines. If you're not familiar,go to the restoration and repair forum,then the hydrostaic drive tractor forum,then post your problem.

Greg

 

[Wayne_H]

So I guess I would be looking for "other options" then.. Any suggestions?

Unfortunately this is a known and very common problem for these machines. The balls are in a plastic thing after you take the flywheel off. It fatiques, your motor overspeeds...

Wayne

 

[kketterer]

Unfortunately this is a known and very common problem for these machines. The balls are in a plastic thing after you take the flywheel off. It fatiques, your motor overspeeds...

Wayne

Hi Wayne, It will run all day long at 3/4 Throttle, But at full, It eventually overspeeds. I will look into the governer again. Thanks.