Electrically befuddled

Meadowhawk

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Ottawa, ON. CANADA
Hello all. Hoping someone can help me eradicate the little gremlin living in my 82 Yamaha XS400RJ. She's a work in progress and was running fine but now will not start. Fuel is flowing and 100 psi pressure on one side and 135 psi on the other. I pulled the plugs (which are only a few weeks old...NGK DR8ES-L) and there's no spark from either side. However, a screwdriver in the plug cap does give off a spark when held near the cooling fins (from a good distance as well). A neighbour suggested an alternate spark plug from a car...which gave off a great spark from an even wider gap than the original NGK. I tried the original NGKs again with a much smaller gap and I did get a very weak spark, not enough to start the motor up again when I put them back in. Has anyone ever experienced this issue?
 
wonder if the spark plugs should be a non resistor variety?
100psi is low needs t be 170ish
Thanks for the response. I was thinking that also, about getting spark plugs with less resistance, but then I wouldn't know which to buy. I'm also thinking that just might be putting a band-aid on a much larger issue which I don't want to be dealing with when I'm far from home.
As for the compression, while testing it my neighbour said anything north of 100psi is good, so your comment had me look it up in my manual, which says between 113.8 ~ 156.4 psi. so now I'm somewhat concerned about the lower compression in my left cylinder.
Another thread came up whereas someone else had a similar issue and it turned out the carbs weren't set correctly and letting in too much fuel in the bowl, which somehow fouled up the plugs. I'll be testing for that next. Hopefully that's the issue because it's a quick fix.
 
Your neighbor isn't wrong but I wouldn't say anything above 100 is good, but rather it will run. Taking the engine into consideration is important, for example a new lawnmower engine may only show 80 or 90 psi, but then it needs to be low for pull starts. When I first got my 78, it ran with one cylinder at 90 and the other at 120, but not well. I also had a cracked head so I did a head job and rering. After that and some break in, both now read 140.
 
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