Yesterday, when I went to start up my 1998 Honda Hornet 600, I got a massive backfire. It’s never happened before and I’m wondering if it’s anything to worry about (damaging valves, etc)? The bike ran fine afterwards, in fact it felt smoother. But I don’t know if that’s because I have changed the oil or it’s just in my head.
Cairnsie13, MCN forums
You'll get a backfire when there is unburnt fuel in the exhaust that gets ignited. If, after the oil change, you turned the engine over a few times without starting it to circulate the oil, that could have pumped some fuel into the exhaust system and given it time to form a vapour cloud which you ignited on start up. An oil change can make a bike feel smoother, so it's not all in your head.