86 EZGO Marathon Baffling Symptom

[SgtP]

I've been having a frustrating issue with my 1986 EZGO Marathon cart. I replaced all the oil and fuel Ines, removed and cleaned the carb, changed the air filter and spark plugs. Then I proceeded to confirm there is spark when the pedal is pressed. The strange issue is with the spark plug removed everything moves with no indication of any problems. The generator, clutch and fly wheel are all moving freely with no abnormal sounds being heard, and fuel is being pumped to the carb. When I put the spark plug back in, everything stops or rotates in a surge like motion and doesn't pick up enough rotational speed to fire. I'm really at a loss and can't get any help where I'm at, as the nearest cart repair shop is two hours away.
Any ideas or suggestions would be greatly appreciated. Thanks.

 

[Diode]

Battery, starter generator or solenoid
Put a voltmeter on the battery and try to start it how low does the voltage go

 

[SgtP]

Fully charged Deep Cycle battery, charged by trickle charger. Started at 13.3VDC and after 3-5min ends up around 12VDC, it slowly drops depending how long I hold down the pedal waiting for it to kick over.

 

[SgtP]

What I really can't wrap my head around is why the generator rotates moving the belt to the crank and clutch, which in turn moves the drive belt with ease when the spark plug is out, but as soon as I put the plug back in, it struggles to move the same pieces!?!?

 

[classycarts]

With the sparkplug removed you eliminated compression. Everything should rotate freely.

Sparkplug removed, stick you finger in the sparkplug hole. Do you get the same results as if you had the sparkplug in the head?

 

[SgtP]

So would it be a safe assumption that the generator needs to produce a certain amount of torque to overcome the compression? If so, the fact that I have no idea how old this generator is as my wife bought this cart four years ago, there's a good chance that the brushes are to far gone to produce the required torque ?

 

[Diode]

Now put your meter on the leads at the starter generator and check the voltage when cranking

 

[SgtP]

Battery - 12.6V
Solenoid - line 12.6V load - 12.3V
Generator top - 11V, bottom - 11V, commutator end fwd - 11V, rvs - 11V
Terminal block top - 11V, bottom - 0V, fwd left - 0V, right - 11V, rvs left 11V, right - 0V

 

[Diode]

On the above test did you hook the negative lead to the batteries or to the generator

 

[SgtP]

Battery, wasn't sure which was negative on the generator.

 

[Diode]

The body of the generator is negative you could have a bad ground strap

 

[SgtP]

Where would that be located? I don't see one attached to the generator.

 

[SgtP]

So I just went out to try and get some measurements withe the negative against the generator casing, and of course Murphy's law, the darn thing cranked and fired as if there was never a problem. Ironically it's the same thing it did to me after installing the new muffler and replacing the oil lines. Then after two trips up a trail behind the house, it didn't want to crank at all as described in my original post. So in terms of measurements, I was getting 12.6 or higher between 14 - 15 depending on how much gas I was giving it. Now I'm paranoid to even take it out of the driveway with the risk of it crapping out on me and having a long walk home. I'm still no further ahead figuring out what the problem is at this point.