VTR250 Spark Plug Arcing

[Dr. Frankenstein]

I got a chance to get back out to the garage and do some tinkering with that VTR250 I brought home a few weeks ago. I got the front forks fixed but didn't have any spark, so checked that out thoroughly and found the connector from the coils was disconnected. Hooked that back up and Voila! I had spark on both plugs, and a pretty good one too! BUT - since the engine is painted black and I didn't have anywhere shiny to place it on, and not knowing if the paint would interfere with it, I used a screwdriver to give the spark somewhere to go and cranked it over.

I got a good spark, but I also saw a nice arc from the plug body to the frame, which is also painted black, and no, I wasn't touching the frame with the screwdriver. The rear plug does not arc. So, do I have a bad plug, a bad boot, or other gremlin?

I haven't had a chance to get some new plugs in it yet, but I'm thinking that might be a solution. It's not arcing through the boot, just the body of the plug, jumping a gap of about an inch. Why would it do that?

[CYBORG]

hairline crack in the plug comes to mind.

[Dr. Frankenstein]

That's what one of my biker buddies said too; I'll change out the plugs and see what happens.

[CYBORG]

often the crack is so small. or even so short, it is hard to see with the naked eye. magnifying glass can help

[CYBORG]

or, just try a different plug

[Dr. Frankenstein]

Yup; put in two new ones and Vroom...!~ Quite the difference. But Dang - $10 a plug?? NGK CR8EH-9's...I was going to get four, thinking they were like $3 apiece...are plugs going up or is it me? Maybe it's the rarity of the bike, I don't know.

[CYBORG]

no, your right. Price of all plugs have gone crazy......at least from back in the day