OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Model 45: Loud Clunk When Engaging Blades

hey guys. Today when i fired up my 20in cylinder morwer. I let it run for a minute lowered the revs right down and engaged the blades. As they engaged there was a loud clunk noise. i took a video but not sure how to post it.

anyone know what it could be and how to fix it.

Youtube video

[video][/video]

Hi 8lueoval,

Well I see you were a happy camper yesterday, I'm sure you know what I mean.

As far as your issue is concerned, can you please take the chain case off and take a close up photo of the drive train set up as I feel this is where the issue lies.

Cheers,
BB

nope i don't get what you mean? haha

post a pic in a second

Hi 8lueoval,

Well Frosty won the Championship over the weekend didn't he and you're a Ford man ?

Anyway regarding your issue, there are two parts that play a major role.

The first one is how much cork is in the primary clutch as I fear there may be none left and if that's the case you have a metal to metal situation and that will create a bang as its a cone (wedge) scenario which is one of the most major grip and bonding situation. The cork would act as a dampener to this gripping action.

The other thing I wanted to ask you is there any reel and bed knife contact at all if you rotate the reel by hand while the machine is not running (of course)?

Both these situations will work against each other, so can you inform me regarding the contact issue before we go any further ? also I note that primary Land Roll chain is grossly out of adjustment which indicated there has been quite a lack of maintenance done on this machine by it's previous tenant.

BTW. Can you furnish us with a close up photo of the bed knife and reel contact area. Lay the machine back onto its handles grips and ensure the sun is shining into this area and then snap away.



Cheers,
BB

I had a similar issue recently and found some free play between the clutch cone and the main shaft wood-ruff key. I replaced that key recently when the engine was off and the 'clunk' when you first engage the cutter is gone.

Might be something to check as you can feel that free-play just by turning the shaft back and forth quickly by hand.

Simon

Hi SimRice and 8lueoval,

That was going to be my third option but I wanted to go through the other two issues first, but you are correct Simon.

Cheers,
BB

oh nar i don't watch the races, the reel spins freely, 100% no contact there. Do i need to adjust the other chain? it does sound like it coming from where the chains are.

ANYONE?

Hi,

Sorry but I think I missed your last post on this thread, things have been rather quiet on the lawnmower front with many people doing other things at this time of year.

Next plan of attack is to set up the reel and bottom blade so there is very light contact between the two and see if the issue is resolved.

Also have you tried Simrice's evaluation of the transfer shaft woodruf key wear ?

Cheers,
BB

Hello 8lueoval and Mod BB

I'm sorry I missed your post of ten days' ago too.
It is the silly season at this time.

As BB said, this is a problem solving and elimination procedure.
The first thing to do is make sure you have a 'contact' set as
per the manufacturer's instructions.

When I listened to your video, it sounded as though the reel
was way clear of the bottom blade. In my experience, excessive non-
contact will produce a harsh primary clutch engagement sound.

It would also be helpful if BB had a close-up photo of the reel
and bottom blade (taken from underneath the front roller), to
assess the condition of the blades.

Hope this helps.
--------------------------
Jack

Ill get a picture this afternoon. I thought the bottom blade and reel weren't suppose to touch. Just miss each other?

How would the blade and the reel not touching cause such a loud noise?

Hello 8lueoval and Mod CJ,

Firstly I hear what you are saying regarding the non contact method for the reel and bed knife, but that method as shown in the Reel adjustment video has now been critically reviewed and is classified as obsolete for Scott Bonnar domestic mowers. It is still relevant for various commercial grade cylinder cut machines with far more advanced set ups and tolerances.

So the correct method is to adjust the reel so that you have just the lightest amount of contact and thus it becomes self sharpening, thus regular adjustments have to be made as routine maintenance. This also places a small amount of back pressure on the drive train system which is good.

BTW your reels and bed knife appear to be in very good shape as they've been recently machined and the bed knife replaced.

Once you've done this procedure let us know how you get on.

Also have you checked that transfer shaft for any free play within the primary clutch housing ?

I am heading off interstate today but taking a laptop with me so I'll be able to correspond with you and see how things are traveling along.


Cheers,
BB

yeah brand new bed knife. i dont know much about these mowers (yet) so whats free play in the clutch?

I'm referring to the play inside the clutch housing when trying to hold the clutch body still with one hand while attempting to twist the transfer shaft back and forth and see if there's any noticeable rotation of the shaft.

Cheers,
BB