I've HEARD of older motors (is it an ancient weed wacker?) interfering with WIRELESS systems because older motors do not have 'the proper ignition noise surpression' ...otherwise I'm with grounding..but since it's not an electrical motor....borrow a weed wacker from someone or bring your own and see what happens....
This is CABL.com posting #355599. Tiny Link: cabl.co/mbEFD