40HP runaway problem

[TerryB]

My 1986 40 HP sat up for a while. The VRO system has been disconnected. When started, the motor CAN run well and smoothly but more often races at maximum RPMs and can only be shut off by disconnectinh the gas supply. Can reconnect gas supply and the same thing happens. I need some direction on this PLEASE!

 

[tashasdaddy]

Re: 40HP runaway problem

check if timing plate is moving correctly. could be stuck. also check throttle linkage.

 

[TerryB]

Re: 40HP runaway problem

Thanks, Tashasdaddy, I appreciate your reply. I have to ask: Should I pull the flywheel and clean everything associated with the moving parts around the coil/sensor area?
TerryB

 

[nightflight]

Re: 40HP runaway problem

Similar thing is going on with my 90,see my post.. let me know what you find. I was suspecting fuel leaking around a float or primer. Not a linkage thing or ignition.

 

[JB]

Re: 40HP runaway problem

Thermal runaway does not involve ignition, if that is what is happening. Needing to disconnect the fuel suggests that it is a thermal runaway. That is bad, bad, bad. Many engines disintegrate in thermal runaway.

But the engine has to be run up past about 2,000rpm without a load for a thermal runaway to get started.

Sticking throttle or sticking stator can start such an event, as daddy suggests.

 

[Randybeall]

Re: 40HP runaway problem

Do not start the engines again till you make sure of what tashasdaddy has told you. I would suggest disconnecting the throttle and shift cables and making sure all the linkages on the engine will return freely to idle stop. Something is not backing off and will lead to a very high priced failure.

 

[Randybeall]

Re: 40HP runaway problem

Ok, I put my thinking hat on while going to a Scout meeting. Check your fuel pump. If it is feeding fuel into the crankcase you can not slow the engine down with out stopping fuel flow. Won't hurt to check linkages but I suspect the fuel pump is where you will find your problem.