Weak intermittant sparks (Ongoing Problem)

[MerlinDudley]

1982 XS400J Maxim
I got it running well, and went to take it for a good run! Being low on fuel, I called at the petrol station, and Yes, you guessed it! The bloody thing wouldn't start! I eventually got it started,(bump started it) and gave it a bit of a thrashing, in taking it a long way round, to home! It seems that now, not only bad starting, but it won't rev, over 5K, no matter how hard I try!
When I got it home, I took the plugs out, and replaced them with new ones. Same problem!
Took the plugs out and tested them for sparks (both set's tested) with the result of an intermittant, weak spark.
Now, I'm thinking that it is possible that the HT Leads, are the problem? As they look to be the original's that were fitted from new! I have been ringing around all the bike shops, and motor factors, in my area, but it seems that no one is stocking Copper Cored, HT leads, anymore?
Would silicon cores, work with such an old electrical system?
What is the difference between the two, apart from the obvious, of one having a metal core, and the other silicon?

Thanks in advance, for any help!

Merlin

 

[arfstrom]

The wires are press on's. My suggestions has always been if if you mess with the plugs, or the coil, shorten up the wire, about .5 inch on both sides of the wire (1in total) to get fresh wire onto the spike (coil side) or the screw on the cap side. That will solve most intermittent plug issues. as far as not going over 5k rpm, that would seem to be a carb issue, or perhaps a battery/charger system that isn't working to spec.

I would suggest perhaps the diaphragm, because the carb has 3 segments of operations, first two are lower speeds, and 5k should put you into the high speed function, which if my memory serves, if the diaphragm cant work, then it wont go faster than the 2nd stage. idk for sure.
idk (I don't know)

 

[MerlinDudley]

Working on the starting problem first. Gas tank,seat, and top engine mounts, removed to get at the nuts holding the coils, Coils removed, cleaned up and clipped the ends of the HT leads,and refitted them into the coils. Now is there a thread that I can get, that tells me how I get the resistance readings, for the primary and secondary coils? Sorry if I seem like a dimwit, but, I have never had to take these readings before, in my 56 years of riding, and maintaining my motorcycles (I have been riding,since I was 9 years old!) On a varied collection of bikes from a Honda C50 Scooterette, to a Harley Davidson 103 ci (1688cc)! Therefore any advice would be very much appreciated!

Merlin

 

[arfstrom]

This is short and sweet. not directly ours, but I think you will get the point.