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-   -   Husqvarna YTH21K46 Knocking Sound (https://www.diychatroom.com/f106/husqvarna-yth21k46-knocking-sound-656293/)

BigJim 03-27-2019 08:05 PM

Husqvarna YTH21K46 Knocking Sound
 
I just bought a used Husqvarna YTH21K46 mower, the motor and all works great. One thing I am a little concerned about is when engaging the cutting deck quickly, there is a loud like knocking. The noise stops as soon as the engine catches up. If I ease into the cutting deck, there is no noise. Any suggestions what I should check? The fellow I bought it from said it was belt slap.

I got such a good deal I figured if I had to fix something, I would come out ahead.

lenaitch 03-27-2019 08:44 PM

Re: Husqvarna YTH21K46 Knocking Sound
 
I don't know anything about Husky specifically but many mower decks use a spring-held tensioning pulley as part of the belt routing. If that spring is shot or improperly installed it could cause belt slap or allow the pulley to hit something. Just a shot.

BigJim 03-27-2019 10:11 PM

Re: Husqvarna YTH21K46 Knocking Sound
 
Quote:

Originally Posted by lenaitch (Post 5802395)
I don't know anything about Husky specifically but many mower decks use a spring-held tensioning pulley as part of the belt routing. If that spring is shot or improperly installed it could cause belt slap or allow the pulley to hit something. Just a shot.

Thanks lenaitch, I will give that a shot and see if that is it. I appreciate your help.

Windows on Wash 03-28-2019 07:50 AM

Re: Husqvarna YTH21K46 Knocking Sound
 
Where are your RPMs when you engage the PTO?

BigJim 03-28-2019 10:54 AM

Re: Husqvarna YTH21K46 Knocking Sound
 
Quote:

Originally Posted by Windows on Wash (Post 5802565)
Where are your RPMs when you engage the PTO?

I don't really know, I would say about 3/4 throttle. I never ran our old mower wide open, but the manual for this one says to run wide open.

lenaitch 03-28-2019 06:18 PM

Re: Husqvarna YTH21K46 Knocking Sound
 
Quote:

Originally Posted by Windows on Wash (Post 5802565)
Where are your RPMs when you engage the PTO?


Good point.


My JD manual says to engage the deck PTO at part throttle. I always figured it was to ease the strain on the electric PTO clutch but a 'hard start' of the deck drive might set things to slappin' and shakin'. A full throttle start on mine won't cause my deck to bang but other designs might.

BigJim 03-28-2019 09:40 PM

Re: Husqvarna YTH21K46 Knocking Sound
 
I am not sure mine is electric PTO. There is a lever behind the steering wheel that I push upward in a 1/4 circle. I have found if I ease into the cutting deck, it doesn't make that noise. I checked all on the deck today and everything is really in great shape, no slack or wobble in anything.

I thought I had really messed up today though. I had cut several stumps real close to the ground and thought it was low enough the blade wouldn't hit it, but it did. It killed the mower from wide open. I had to pull the lever to disengage the trans then pulled the mower backwards.

I was pretty perplexed about the possibility of messing up the mower that was one day old to me. I tried to crank it and it did crank but wouldn't go forward or backwards. I turned it off and checked every thing, then saw I have left the lever out that disengages the trans. LOL whew, I am a happy camper again.

I noticed the deck was cutting really really low on the right side, I checked several things and found when I hit the stump it bent the blade at a 90 degree about 3 or 4 inches from the outside edge. I went and bought new blades today.

Over all I am really happy with the mower, I guess I will just baby the mower and fix whatever tears up. I really do appreciate all your help.

lenaitch 03-29-2019 04:32 PM

Re: Husqvarna YTH21K46 Knocking Sound
 
Quote:

Originally Posted by BigJim (Post 5803127)
I am not sure mine is electric PTO. There is a lever behind the steering wheel that I push upward in a 1/4 circle. I have found if I ease into the cutting deck, it doesn't make that noise. I checked all on the deck today and everything is really in great shape, no slack or wobble in anything.

I thought I had really messed up today though. I had cut several stumps real close to the ground and thought it was low enough the blade wouldn't hit it, but it did. It killed the mower from wide open. I had to pull the lever to disengage the trans then pulled the mower backwards.

I was pretty perplexed about the possibility of messing up the mower that was one day old to me. I tried to crank it and it did crank but wouldn't go forward or backwards. I turned it off and checked every thing, then saw I have left the lever out that disengages the trans. LOL whew, I am a happy camper again.

I noticed the deck was cutting really really low on the right side, I checked several things and found when I hit the stump it bent the blade at a 90 degree about 3 or 4 inches from the outside edge. I went and bought new blades today.

Over all I am really happy with the mower, I guess I will just baby the mower and fix whatever tears up. I really do appreciate all your help.


Close call. You could have bend something really important (read: expensive). Sounds like you've found your own solution to prevent the noise. It sounds like you PTO could be mechanically engaged. I'm not familiar with those. Maybe part of the linkage was banging or the torque of a high-RPM engagement transmitted some vibration.

BigJim 04-09-2019 11:23 PM

Re: Husqvarna YTH21K46 Knocking Sound
 
Found the problem with the mower, the bolts holding the motor to the frame was loose. Tightened the bolts, no more knocking.


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