Satoh 650G won't stay running under full load

[Ironbird]

Hello, I hope you can assist me-

I recently purchased an old Satoh 650G, I believe it has the 70-72 Mazda 4-cylinder gas motor in it. The problem I am having is as follows:

I have to choke it quite a bit at low idle when I first start it up and wait a few minutes for it to come up to temperature. I can then give it some gas and bring the RPM's up so I can start to drive it. At that time I can fully open the choke and it runs fine. Seems normal so far right?

Anyway, once I bring the RPM's up to around 2500-3000 I turn on my
PTO and start to mow. It will go for a few minutes and then the motor will act like it is losing power and the RPM's will decrease. I have to reach for the choke again to keep it running. The bottom line is that it seems like once I try to put a full load on it (driving with full PTO on) it stalls out. Once it stalls out it is somewhat hard to start and next to impossibleto get the RPM's back up without stalling again. I have already changed out plugs, wires, dist cap and rotor as well as the coil. For the fuel system I have totally drained the fuel tank and replaced old gas with new 93 octane fuel. One of the fuel hoses looked bad so I replaced that as well. Likewise, I replaced the fuel filter for good measure. I have cleaned the carb out with carb cleaner. I thought that the fuel pump may be bad but when I disconnect it and check it (move mech arm up/down) I seem to be getting good vacuum from both ends.

I'm about at my wits end. Do you have any suggestions? Would replacing the fuel pump with a small electrical unit be the next thing to try? If it comes down to replacing the carb what is available?

Thanks for any guidance you can give. .

-Ironbird

 

[CCWKen]

I seem to be getting good vacuum from both ends.

If this is the fuel pump, something is wrong. One side should have vacuum and the other side pressure. Having to run the choke sounds like it's starving for fuel.

Here's a few things to check:

1. Fuel tank strainer
2. Fuel pressure
3. Carb float setting
4. Sticking carb float valve
5. Leaking vacuum line or intake gasket

Hope this helps but 3k rpm seems a bit high for that engine. To prolong gearbox life, engage the pto at idle and then increase throttle.

 

[mit]

sounds like fuel starved.the pump should spit out fuel when you move the mechanical arm.could be a defective valve in the fuel pump.you are possibly getting a gravity feed to the engine which is not sufficient to run the engine.check out the fuel pump more closely.also check the vent on the fuel cap.

 

[rwalls1]

I am having a similar problem with my 650G. The mechanical fuel pump on mine has been replaced with an electric one. It seems to work fine for about 10 min. and then stops. I am thinking of buying a new pump, but need to know what psi the fuel pump should be. Anyone know?
Thanks
Ron

 

[mit]

A pump of this type should be adequate for your application.the pump needs to be low pressure for a carburator application.

 

[Beaucefus]

3 1/2 # pressure on that fuel pump,
also check intake manifold gasket, good luck