Hi Shannath15, welcome to the men's shed
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I have copied one of your photos and surrounded the crankcase of the engine in purple and I think I can just make out the number -green arrow.
That 125cc motor is a pearler of a powerplant that will last a long time with the 25:1 fuel mix. You must mix 200ml of 2 stroke oil to five litres of petrol to make up the fuel for these. Never ever put in pure petrol without this oil mixed thoroughly in first. It's fatal.
