2005 bomb gtx 500ss

i have a 2005 GTX 500ss i bought for the girl friend ,, sled is mint... took it home last season , ran it in the shop and shut it off and lost spark ,, tried just about everything i could without throwing parts at it. spoke with guy i bought it from ( language barrier ) he said it happen before,, told me to spin the electric starter and pull the tether off at the same time. a couple time and the spark cam back.. ran it for the winter ,, may of happen again , but this worked each time.. now it time to get it out for the winter and no spark again.. tried his trick which makes no sence anyway , but still nothing . has to be test i can do to find what part is failing.. i not a sled mechanic , don't like small engines. and i don not like the way they over complicate a simple system.. help is needed.. thanks