Looking for the Source Coil Partzilla part# 3M285512-20-00. Partzilla list several other years/models but it's still not available. What is another source coil that can work ? I do see on the bay one for a Yamaha golf cart part# 8G8-85511-20-00 could this work ? I'm not an expert on these ignitions so any help is certainly appreciated. I was told that a YZ ignition might work but I would lose some bottom end which does not bother me.

Thanks

You generally can't use coils from other models.  And yes, no longer available though sometimes NOS coils pop up on ebay, 

As I said in one of your other threads, your ignition has a history of strange issues and even replacing the coils with new may not work.  As much as that doesn't make sense, I've found it to be true.  (I have a 1980 MX175 ignition with both coils replaced and it still doesn't run right) I think the flywheels might go bad or something...  it's slightly smaller than the DT175 version. 

Thank you for replying

In searching for one I did find Rick's Motorsport Electrics in New Hampshire will rebuild your source coil relatively inexpensive. I sent them an email for the specifics and it appears you just send them the source coil, the stator plate and lead wire harness.

Off of their website:

This part fits the following vehicles:

Rebuilt Yamaha Source Coil 22_Y114 for a 1990 Yamaha Dirt Bike RT100
Rebuilt Yamaha Source Coil 22_Y114 for a 1992 Yamaha Dirt Bike RT100
Rebuilt Yamaha Source Coil 22_Y114 for a 1993 Yamaha Dirt Bike RT100
Rebuilt Yamaha Source Coil 22_Y114 for a 1994 Yamaha Dirt Bike RT100
Rebuilt Yamaha Source Coil 22_Y114 for a 1995 Yamaha Dirt Bike RT100
Rebuilt Yamaha Source Coil 22_Y114 for a 1979 Yamaha Dirt Bike MX175
Rebuilt Yamaha Source Coil 22_Y114 for a 1980 Yamaha Dirt Bike MX175
Rebuilt Yamaha Source Coil 22_Y114 for a 1981 Yamaha Dirt Bike MX175

Maybe you'll have better luck with that than I did. 

More info...  my original stator coil measured within Yamaha specs.  So did Terry's.  The Ricky Stator coil I got ran different but still not right.  I did a bunch of parts swapping and testing...  even used an oscilloscope.  Terry found a NOS Yamaha stator coil for his, you can see how great it worked in the video.

If your stator coil is out of spec then maybe it's worth a shot. 

Spec is here:

Cool thanks

The scope data showed lower voltages from stator coil on the "bad" ignitions than the DT175 stator that runs great.  Since I literally had 4 different stator coils...  two of them new..  I suspected it might be the magnets in the flywheels were not as strong as they need to be or something?

DT175 CDI box is the same part and I swapped around several of those with no improvement or change with the "bad" stators.  I wish I would have had a good MX ignition to use the flywheel from but all I had was the two flywheels from the "bad" ignitions.  

As I probably said already, others have had that same mysterious ignition issue with the 80-81 MX175 and nobody ever fixed it...  some didn't try...  all ended up replacing the ignition system with one from a running bike and/or a different model.