What is this noise?!

[Houseboater]

I finally got another Blaster but seems she is in need of some work. Its an 03 that my uncle had for a few years. He rebuilt the top and bottom end about a year ago and never had an issue since. A few weeks ago it started making a strange noise which I have found on a youtube video from someone else with the same noise.

The bike starts first or second kick, runs great and has all the gears. Shifts smooth etc. At the time of the rebuild he also installed a new clutch.

Anyone know what this might be and if I should be worried?

Vid Yamaha Blaster Engine Noise - YouTube

 

[harley1-5]

sounds like piston slap I would leak test and then pull top end and check clearances

 

[Houseboater]

Kinda what I was afraid of. Ill do that on one of my off days this week.

 

[harley1-5]

yea if it is piston slap and you keep running it it will eventually break the piston skirt and contaminate the crank bearrings and possibly do lots of other lovely expensive tricks

 

[Sauce440]

same noise mine makes but not as bad. its piston slop

 

[Jradd127]

If it is a slap deff correct it, I'm just got one from user error on mine & am now paying about what I payed for the bike to fix it