Hayter harrier 56 intermittently lost its spark

[Martin]

I have a problem that is confusing me. I have a harrier 56 that I'm trying to repair at the moment, it started life as a normal harrier 56 I think 560h, but customer wanted electric start fitted so that was done somewhere else and for the last 3 years it has come into us as it looses its spark on electric start but it sparks and runs fine on recoil. We have checked continuity from key to battery, from battery to starter, from starter to coil and everywhere else. Everything looks good and we can't work it out.