Strange single clang noise while wheeling in 1st gear

Hi guys,

I have a problem with my bike.
When i'm popping my front wheel up in the first gear (with clutch), when the front tire gets up in the air i hear strange single 'clang' sound coming from the front of the bike.
It's like something is hitting something else. I checked if there is any movement in the wheel or if there is a problem with head bearing (there is no problem with steering) but couldn't find any problem.

What do you think may be the cause?

Thanks,
M.

On my bicycle, it is just the sag coming out of the front fork , when I lift it...?

My thoughts are the front topping out when you lift off. Only in 1st, what about second and third gear wheelies?? Try hitting a jump and see if you hear the same noise.

Could be time for a fork rebuild.....