MM BF restoration-more progress

[Retired Iron Peddler]

Our BF has been very slow to almost impossible to crank, depending on the temperature, on 6-volts since it was new and the reason it was changed over to 12-volts (positive ground) many years ago. We tried an 8-volt battery back in the 60s when they were available, but even it wouldn't spin the engine as it should to start. Starting the tractor on 12-volts using the original 6-volt starter has been problem free for at last 20-25 years.

Bill

 

[flusher]

Our BF has been very slow to almost impossible to crank, depending on the temperature, on 6-volts since it was new and the reason it was changed over to 12-volts (positive ground) many years ago. We tried an 8-volt battery back in the 60s when they were available, but even it wouldn't spin the engine as it should to start. Starting the tractor on 12-volts using the original 6-volt starter has been problem free for at last 20-25 years.

Bill

Thanks for the info.

Makes me wonder if MM got a lot of customer complaints about this in the 1950s when the BF was being produced. I wonder if Hercules ran their new engines on a run stand before shipping them to break them in, seat the rings, and loosen up the engine for the 6V starter to crank fast enough to get the engine running.

Going 12V (pos gnd) is on my mind. My concern is that 12V will cause the bendix to slap the ring gear on the flywheel too hard, possibly damaging the gear teeth. From your experience, it looks like this hasn't been a problem with your BF. Need to head for NAPA to get a 12V coil and try this out.

 

[Retired Iron Peddler]

The only caution running 12-volts through a 6-volt starter is not stay on the starter too long. The BF starts so easy on 12-volts, I never have to crank it very long.

Bill

 

[flusher]

The only caution running 12-volts through a 6-volt starter is not stay on the starter too long. The BF starts so easy on 12-volts, I never have to crank it very long.

Bill

Good advice.

When you hit the start button with 12V on that 6V starter, the inrush current will be double what it is at 6V and the heat generated in the starter winding will be 4 times higher. So short cranking time is important. Of course, when the starter is spinning, the back voltage (back emf) will lower the current in the winding somewhat, but smoking the winding insulation is still a concern.

What I plan to do is to hand crank the engine while fiddling with the ignition and carb settings until I get some sort of burp out of the engine. And then hit the starter with 12V and see if I can get the engine to catch.