engine knock when mower deck engaged ?

[k+s 1277 1]

I have a k-301 kohler engine runs good I put it on my 76 b-100 this is the second good running k-301 12 hp. funny they both knock when I engage the mower deck. I changed out the clutch still knocks. any ideas?? guess I better check the points first, I set them at 18 on the other engine I had on it and it still had a knock but not as loud, im running unleaded plus gas in it. has new points condencer,coil,spark plug.?

Edited May 30, 2015 by k+s 1277

[Digger 66 3,476]

Kind of ironic that the knocks occur on two different engines with the s a m e  deck .
I'd be checking the deck pulleys / spindles  out for smooth operation 

[19richie66 16,879]

Deck bent? Blade tapping a baffle? Idler pulley arm loose and thumping? Just a thought.

[Racinbob 10,256]

I can't imaging it's coming from the motor. Something on the deck or it's drive is amuck.

[k+s 1277 1]

thankyou for your comments gentlemen, but the noise is coming from the engine. I did try setting the points at 18 knock not as loud just wonder if its the aftermarket points. because that's why I changed the motor,because of the knock in that motor they both do the same,i took the mower deck off and going up hill it knocks a little. it has me stumped. any other ideas besides tearing it down and rebuilding it??.

[Digger 66 3,476]

You could test for pre-ignition by dumping some 92 in the tank & see if it goes away .
Then at least You'll know if you have a spark timing issue .

[Fordiesel69 199]

Please make a video.  I will be able hear if it is spark knock or rod slap.  Knocking kohlers are kinda common.  Its how bad the knock is that determines how long the engine will last.  If the rod is too loose, it may only make it a few more hours.