Vintage Dirt Bike Q & A

This bike is running great but is killing spark plugs like crazy. My only last issue is spark plugs. I'm going through them like candy. They are shorting out. They are not fouling but literally shorting out. Bike starts great and runs fine and then will just die. Pull the plug and replace it and it starts up again then will die. The plugs will arc from the plug to the case but not in the gap after that. Nice blue spark but nothing in the gap it just shorts straight to the outside of the plug. Any ideas what could be shorting out the plugs? I don't have a battery does that matter. I've been running it without a battery.

the battery on the MT will not affect the Ignition system.do you have a good strong blue spark with a new plug? are you running the engine long enough for it to warm up fully?i would also check the carb and oil pump (if it has one) settings.

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

You ARE describing exactly what a fouled plug shows up like. Arcs inside plug or just jumps across way up inside where you won't see it. The wet fuel carries the current. Your too rich if it is doing that quickly. Are you running the injector? What oil? What plug? Slow speed putting around or riding it hard? When you pull a fouled plug away from head there will be a spark from plug to head. Spark has to try to go to ground.

I'm running about a 32:1 mix. I've been running without an air cleaner because It just came in. I wasn't sure how the air screw worked so that sounds about right. I switched from #9 plugs to #8 and they aren't fouling. Just got a Uni 4 inch filter and oiled it up and its way rich now. When I run out of gas and it leans out this thing runs like a beast for a few seconds before it dies. So hopefully when I get the air screw in I can dial this in. Any advice on screw adjustment would be outstanding. Thanks for all the help so far.