ybr 125 trip meter/speedo

Hello guys.

My ybr fell over the other day. Rolled off the side stand. Landed on the left side, no real damage but the trip meter reset knob took a whack. Since then, the trip meter can be reset, but only clocks up to 7miles, then sticks.

I've taken the speedo out to inspect the innards - but there doesn't seem a way to get it open. Is this a factory sealed unit? Or is there a way into this that I've missed?

I use the trip meter as my fuel gauge, so its loss is a pain. Is buying a new unit the only option here?

Your help greatly appreciated.

Thanks, Tony