Very loud clapping noise from bottom end of engine!

Hi all,

This 2018 WR250R has been sitting for about a year and only has 800 miles on the clock. Already had to replace the fuel pump, fuel pressure regulator and lift pump (4.7gln IMS tank) in order to get the bike running again. However, when idling and opening the throttle rapidly, there is VERY loud tap/clunking/clapping noise that appears to come from the bottom end. Sometimes it will even kill the engine doing that.

See this video. Its most evident towards the end of the video:


Any suggestions are welcome.

First of all, it is alarming that you had to change the fuel pump, regulator, and secondary pump on a three-year old bike with less than a thousand miles. I had to do all of them, but over a period of five years on a 2008 bike that has more than 20k miles and has been used hard.

To the specific problem, it could be a crankshaft or piston issue, but it's difficult to imagine how this could have happened to a bike with just 800 miles. If it were me I would start by the least invasive tests and go from there, i.e. do a compression test first, if below specs then check valve clearance, etc.