NSR 125 engine 'knocking'

[wcr]

Recently bought NSR 125 R-1 (2003) with 15k miles, hearing a knocking sound from the engine I replaced the piston and rings (barrel is fine) as I assumed it was piston slap.

Not so, as I started it with new piston the dreaded knocking is still there. It's not the drone you normally get from big end/crank bearings, it sounds more like a clutch spring coming loose and hitting the side casing ( its not that as the noise remains exacty the same with clutch in or out)

The noise go's away above 3,000rpm and gets quieter as the engine gets warm.

Not yet had the side casings off but a previous owner has as there is blue RTV sealant (instant gasket) around the NS casing.

This knocking is rather loud when cold, quietings down slighly when hot, disapears when above 3-4000rpm.

[alains]

it could be the balancer or it's bearing
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