Problems with the cutting deck

[Bange]

Evolution:
I placed an angle bracket with several holes that represent different angles of the steel cable to the axis of the tensioner pulley support... in relation to the initially chosen point, the vibration improved a lot in holes 2 and 3, getting very little at maximum rotation, but at low rotation, almost no improvement is noticed.
It could be that I'm too picky, but if it resolves low, the high will also be resolved satisfactorily.


I also replaced the original bearings on the brake arms with ball bearings... I haven't tested it yet, but it's already been noticed manually that it was very soft and this should reduce the noise a little.

As the diameter of the new bearings are larger, I had to readjust the grooves in the tensioner pulley support.

 

[Bange]

I think I'm working with cold iron... everything I've been doing seems to have little or no effect on the vibration item... it's possible there are several causes and I'm eliminating each one, but the main one remains.
I don't have anything to turn the engine slowly, so I removed the spark plug, the belt and scratched the key to see the pulley turning and I didn't notice any play in its edges, but I noticed a variation in the groove that could be the root cause.
Removing this pulley must not be easy without the specific tool and I would like to remove it and analyze it on the lathe... does anyone have any tips to make the procedure easier? HELP!

 

[bertsmobile1]

You are solving a problem that does not exist as the deck should always be running at full speed
There is no such animal as a vibration free deck even more so when powered by a single cylinder engine that produces power pulses
Because the engine pulls forward on the left side , you get a twisting moment every times the engine fires ( 3500 rpm ) so you get a 3500Hz vibration for the engine alone.
Add to that the belt has a join so every time the join runs over the pulleys it will cause a vibration, a problem many lathe users have that can cause chatter , particulalry if the lathe has a flat belt drive
Next vibration causer is the actual shape of the deck itself as the blades are identical but the air space above them is not

When Victa made the Vortex push mower, they found that over 80% of the noise was generated by the blades so they made a weird blade carrier ( swing back blades ) and strange curved blades with no flutes to eliminate the under deck noise and they are quieter than a Honda in use which says a lot for a 2 stroke engine

Greenfield mowers ( local brand ) have a true parrallelogram lifting system that has bushes at every pivot point and that removes both noise & vibration

 

[Bange]

I agree that the cutting speed is always maximum, but I use it a little lower for sites with only leaves, which don't need high RPM.
As I said before, it could be that I am very demanding and if the low is resolved, the high will be very smooth.
Without the weight of the cutting set, the vibration of the motor alone is practically non-existent and I would like it to remain the same with the deck, so analyzing the pulley on the lathe is what is missing, as the rest has already been settled... apart from that, just a Spartan solution, which is my plan "B".

 

[Bange]

Well, unable to turn the engine shaft very slowly, I tried to set the lowest possible speed by moving the carburetor and the problem is now evident, leaving no doubt (for me) that this is the root cause of the deck oscillation.

 

[GrumpyCat]

That pulley doesn't look to be true.

 

[bertsmobile1]

Yes

 

[Bange]

Just like I didn't understand!?!?

 

[Bange]

An internet seller says this pulley is the same for Murray and Husqvarna LT 131 and LT 151.
Do you confirm this?

 

[bertsmobile1]

Find the part number
Use that to search on an after market site .
If you get a hit then click on the More info / specifications etc and yo will get a list of all of the mowers it fits