lawn mower engine knocks at startup

[hemitom]

Sounds to make like the hub is fine , with the blade removed there should be very minimal movement on the shaft, which you are describing.

 

[The motor guy]

so then what else could cause the problem? Wouldn't it be knocking at high rpm if it was a rod knock?

 

[hemitom]

I would tend to agree that rod knock would increase with r.p.m!.
I'm wondering if your having a slight timing issue.

try swapping your old plug back in.

 

[The motor guy]

thats the first thing i did and it still does it.

 

[Propflux01]

I still say either flywheel or blade adapter/hub key. Provided nothing part-wise has been changed before the knocking started. Usually rods start talking when the engine is at speed but not loaded or on the way back down to idle, yours is described as both ways. If there is any slop in your blade adapter/hub, this could account for why your getting it coming up to speed, and going down to idle.

 

[The motor guy]

It ended up being that the engine was loose.

 

[The motor guy]

I can't believe I didn't check this.

 

[01rangerxl]

Glad you figured it out. That can happen sometimes, but usually by the time it is noticed the deck is severely damaged.