I am trying to find some add-on sound effects for my new MOXF8. I have a MO6 and a PSR 423. The 423 actually has some effects that I wish the MOXF had. The tire screech, crash, jet plane, etc. I contacted Yamaha and they said I could not copy from the PSR and import to the MOXF. Does anyone have any other suggestions?  Thank you.

Here is one source for free sound effects.  These are in Mp3 format, and would need to be converted to WAV to utilize.

Here is another source of sound effects (thanks 5pinDIN).

You will need a Flash board installed in your MOXF.

Do you know how to prepare and LOAD WAV files into the machine?

If not, take a look at This Document and also This Thread.

Those extra SFX were part of the Yamaha XG format compared to only the few SFX of the GM format.
Another option could be -
Some can be found in the MOXF PDR64 SFX Drum Kit Voices or find the respective waveform and tweak it

Thank you very much for the responses. I will attempt to import a WAV file. I could convert the mp3 to WAV through Audacity.