Fouled sparkplug, poor power and pinging sound

**sgurtman** · 8th November 2013, 19:00

Hey guys,

I have got another issue on my classic scooter (FN 75). I first noticed a pinging sound a week ago. It only happens at idle. I figured it was detonation or pre-ignition so I turned up the idle mixture a bit. The idle speed increased and the sound went away except for occasional pings. When it's happening its a metallic clanging sound that seems to be in line with each rev. I first thought it maybe was a transmission or clutch problem but I'm not so sure now. Reason being, is that my scooter has slowly lost power over the past few days. Top end power seems fine but low end got so bad I tried replacing the spark plug today. So the low end power is back but I wonder if the power loss was caused by whatever is causing the pinging noise. The pinging sound is still there after I replaced the spark so it's not that. I'm not sure what else it could be besides the mixture or spark. I also put the 98 octane gas in so it's not that either.
Any thoughts?

**Drew** · 8th November 2013, 19:16

I would be surprised if you can get it to pre ignite at idle, and not burn a hole in the piston before the end of the driveway.

Anyhoo. Do a compression test I reckon.