New top end on bottom end, very low sound to exhaust

[SpecializedMountainMoto]

I recently put a new top end on a used bottom end that I bought here in the swap shop, the piston is the same type and it is not hitting the plug or anything like that, but I have noticed it has a very deep exhaust tone way different than my other engine (gt2b) and is very slow to rev out. Anyone have any ideas why this may be? I already checked to make sure piston is not backwards (ring guides toward the carb)

 

[maniac57]

Pull the intake and see if the piston is blocking the port at bottom dead center.
I've seen a couple engines that needed the piston skirt trimmed to allow flow into the bottom end at BDC. Might be your issue because of the slow revving.

 

[Greg58]

Don't you mean tdc maniac?

 

[SpecializedMountainMoto]

Yeah that's what I was thinking too TDC, but the piston is the same as the other exactly, neither trimmed

 

[SpecializedMountainMoto]

Also it revs quick with the clutch in, only thing I can think of is I had to bend open the new rings slightly to get them over the piston

 

[Greg58]

If you have a new piston, rings and cylinder how many miles do you have on it? It could just need a little more break in time.

 

[SpecializedMountainMoto]

Only a few maybe it just needs more break in time, but my other motor never sounded like that very deep almost like a four stroke