Spark Plugs
#1
Spark Plugs
Hey All,
I ride a 1990 FXSTC EVO.
My cylinders are burning differently.
Front cylinders is burning hot and had detonations. I measured the gap and it was much larger than .040 and the rear is black and sooty.
I had a lot of backfires, then I replaced the plugs
This happens after maybe 60 miles on new plugs.
Could this be a coil or plug wire issues?
I thought maybe the battery, but I would think that both plugs would be black sooty if it was a weak battery.
Any thoughts?
Thanks,
Joe
I ride a 1990 FXSTC EVO.
My cylinders are burning differently.
Front cylinders is burning hot and had detonations. I measured the gap and it was much larger than .040 and the rear is black and sooty.
I had a lot of backfires, then I replaced the plugs
This happens after maybe 60 miles on new plugs.
Could this be a coil or plug wire issues?
I thought maybe the battery, but I would think that both plugs would be black sooty if it was a weak battery.
Any thoughts?
Thanks,
Joe
#3
Ok, inquiring minds wanna know.... What's with spraying wd-40? Where are you spraying it, and do you do it while it's running?
#5
#6
I'm no mechanic, but maybe an air leak will cause some issues with your plugs? As simple as these things are, I'd look into the manifold leak and then work your way through; plug wire may be the culprit, but why is one too lean? You have something strange going on. I can see this happening on a EFI bike, but a simple carb'd bike? I'd say you have some air getting in, but again, I'm no mechanic. I hope you figure it out, cause I'm sure it will help us all someday.
#7
Join Date: Dec 2010
Location: Coromandel Peninsula New Zealand
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#8
#9
#10
Did you try snugging all the carb mounting bolts and intake bolts? Really sounds like an intake leak on front cylinder. The extra air coming in leans out the mixture ( radically in your case) causing the symptoms you have; preignition, overheating,and plug failure. I would not ride it until it was fixed or you'll burn a hole in that front piston.
On a normally running Twin ( with carb) the rear cylinder plug will always look hotter as that cylinder has a harder time getting air to cool it.
On a normally running Twin ( with carb) the rear cylinder plug will always look hotter as that cylinder has a harder time getting air to cool it.