I have a 70cc kit on a Honda NU50 Urban express. Spent the day cleaning carb, and upjetting to an 88 from an 85. I also put on a pod air filter rather than the stock filter.
It had been bleeding oil from both exhaust port and spark plug hole. Plug was sooty looking but not really oily looking. Lately it had been making an odd popping noise in the exhaust when I've been putting the bike away. It kind of sounds how metal does when it gets really hot and cools in the air. It had been running really slow.
After the changes above, I took it riding and it really goes fast. At WOT it's fine, but when I throttle down to about 10 mph I hear this putt, putt, putt noise. when stopped and on stand, it still made that popping sound like metal contracting.
I put the stock air box back on and will try WOT with that again to see how it feels. Any ideas of what else I should look for while I have it out? If the stock filter setup slows it back down, ideas? I figure I can try putting the new filter on, but I guess I'm concerned it will run too lean at that point with that strange noise.
Any help is appreciated.