Knocking Question

[Wisco_blaster]

Hello, new to the forum. I bought my first blaster project that had "piston slap" according the the previous owner. it was taken apart when i got it and had scoring on the cylinder walls and piston. I Just did a top end (the jug is just hand tight) and when pressing the kick start by hand i notice a slight knock sound. Not sure if this is a sign of a bad crank or not. Just would like and opinion is the motor should be silent when spinning by hand.

Thanks!

 

[OConnor Racing]

You should have no up and down play in the rod.

 

[Wisco_blaster]

There was no play up and down, but i could most definitely wiggle side to side. I would just like an opinion before i try and fire it up and trash my new top end bore and hone.

 

[Wisco_blaster]

any other input? Basically asking if when the motor is turned over by hand (pushing down on the kick start) with the head off should it rotate pretty much silent. Or can there be some rotating noise...

 

[Markblaster]

Did you replace the cylinder of get it cleaned up for a new piston? Could it be piston ring catching the edge of one of the ports? Port edges chamfered.

 

[Wisco_blaster]

Yes cylinder was professionally bored and binned to the specific wiseco piston. The ports were also chamfered. I think im going to try and fire it up and see what I've got.

 

[OConnor Racing]

What's the side clearance of the rod?

 

[Awk08]

I think im going to try and fire it up and see what I've got.

what you may have is a pile of broken parts and lost $
"start it to see what happens" isn't in any manual or video I know of


I'd pull the top end and inspect the rod play and clearance as suggested above.