Rain Issues

[old son]

The engine in my Gen 1misses quite a lot when its raining hard. I think I need to cut the HT leads down and make a new joint. Am I right I need to unscrew the lead from the cap. cut 5mm or so off and refix

I don't think it can be much else, if I spray with WD45 before I leave the bike behaves much better.

Thanks