The spark problem your haveing sounds like a weak coil - check your wireing back to your coil and see if its shooting through to ground. if not then try a different coil. sounds liek it´s just not a hot enough spark to ignite but still enough to give you a jolt. LOL The value of your 1979 XT500 : Excellent: $1,675 , Very Good: $1,250 ,Good: $800 , Fair: $400 This is according to NADA Consumer guidlines. I bought a 250 for 400.00 and it runs like a scalded cat. But I am Getting a xt500 this weak cause I want more GUTS on the road. I have seen them non running all the parts there for as low as 75.00 all the way up for a really nice restored xt500 with low miles at 2500.00 - it just depends on your area and teh condition and really, if you have more than a few lookers who like old diggers like these.