Aprilia RS125 2008 Grinding Noise?

[dom12213]

My Aprilia is making a whirring/grinding noise. I really can't explain it, but it is quite loud and unnerving. I have taken the magneto cover off, and nothing seemed out of the ordinary. I have taken the clutch off, and the clutch and all the balance shaft gears etc. are mint. I have checked for crank bearing play, and there appears to be no play whatsoever.

Completely lost to be honest, because short of the noise and slight vibrations that coincide, the bike runs perfectly...

[dom12213]

Here is a video of the bike running.

[Casper]

That sounds like the piston slap i had when i fucked my DT125. New rings of your lucky but top end overhaul is more likely. Drop the oil and see if you have any metal in the oil from the rings.

[Just_James]

Yep, sounds like top end may be unhappy.

Does it feel down on power? I'd do a compression test and take it from there.
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Current Bikes / Projects: 1999 Rieju RS1 50
Previous bikes - 1986 DT125R (field bike), 1989 KX250, 1980 KX420 (with 500cc big bore), 1992 YZ250, 1988 KX500, 1989 XR250R, 1988 VFR400R NC24, 1999 Cagiva Mito 125, 2008 Rieju RS2 50 , 1993 Honda NSR 125

[dom12213]

Pulled the oil earlier, and I don't think there was a single metal shaving I'm it. Doesn't feel down on power whatsoever either. New piston and rings 1500 miles ago according to the owner (who I believe). I haven't got a compression tester to hand, but I will get one on Monday. One other thing I noticed, was when I took the magneto cover off, the starter cog was worn down quite considerably, and the whole assembly was suprisingly loose. Any chance it's the cogs on the starter motor are engaging and grinding?

[Kickstart]