New Blaster vibrating under high revs

So I am finishing my 3rd Blaster and this one feels really strong with nice clean revving except for the Vibration when revving past around 1/2 throttle.

Stock Exhaust
230 main jet.

Previous owner installed 67mm Piston when the motor seized a year ago.

This Blaster really feels strong in the rev range compared to the other 2 but the Vibration bothers me.

I have checked the mounting bolts and they are secured.
Will check counter balance timing tonight but if that is right, can it be that the oversized piston is causing the slight imbalance? and if that IS the case, how would I rebalance it?

TIA

Nope. It's really small. More like a resonance when revving high.

I am really not the expert but I don't know why the screaming on top revs and slight vibration gives me a feeling the engine is running lean.

with the 67mm Piston added and no other mods, I have upped the Main Jet from 230 to 240 last night. Will take a ride this afternoon and feel if there is a difference. Plug chopping will happen soon though.

PS: The vibration is very small.

Larry's Shee said:

Did you use a reputable shop for machine work?

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Nope, I do all work on my bikes myself. This one, however, I bought and the previous owner did the work. Good question though. Think I will touch base with him and ask who did the honing/boring of the cylinder.

Larry's Shee said:

Do you have the rubber plugs between the find?

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Out of the six, one is missing, front right.

Larry's Shee said:

What mods do you have?

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Bike has no mods, except for the oversized piston that was installed previously when engine seized.

Airbox lid was missing when I got it. I got a new one and installed it because the bike has standard header and exhaust. Also upped the Main Jet to 240 from 230 out of fear of running lean. Havent done plug chops yet but since I upped the Main Jet, the engine temp became noticeably less so I think I am heading the right way.

Larry's Shee said:

Do you know anyone else that has a Blaster? You can compare to?
Have you ever ridden a 2stroke motor cycle to compare to?

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That is exactly what I am doing. I have 3 blasters. 2 have been fixed up and busy with the 3rd.