Most common fault you come across?

[Detonation]

My bikes not been starting off the switch for a week now and I thaught it was the battery.
I stuck it on charge and the trickle charger says its fully charged (I'm still gunna leave it on for a few hours)
If its turns out to not be the battery then it's gotta be the starter solonoid.
Starter solonoide seem to be my most common problem.
In just 8.5 years ive Replaced one on my derbi GPR, one on my Zx6E, One on my CBR, one on my VFR, 2 on my Marauder and 1 on my Z750 now I might end up haveing to replace the XJ's one.
I've never had any other fault as many times.
It's the most common thing I replace on mates bikes aswell.

Stuck floats seem to come second

What fault do you lot see the most?

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