Coronet vibration after new blade belt

[apbling 0]

Hello All,

New member here, so I apologize if I'm in the wrong section. I have what I believe is a '95 Simplicity Coronet w/ the 12.5 HP Kohler hydrostatic, 34" cut. It was a hand-me-down from my folks. This mower has been great and, unfortunately, been neglected - not in the sense of being left outside, but just very little maintenance has been done, however it just keeps going...

Anyway, I ate the blade belt yesterday. Replaced with an OEM one and life went on, or so I thought. I get a very odd vibration now. It is a very rhythmic cyclical vibration... like hum hum hum HUM HUM HUM hum hum hum (repeat) when the blades are engaged. Does not affect the cut at all. Does not do this when the blades are disengaged and did not appear until I got the new belt. My blades are older and need replacing, so I figured maybe they were out of balance, but I am wondering if maybe it's something more. I am assuming there are bearings on shafts for the blades - could one of those be going out and now it shows up with a nice tight belt? I even disengaged the blades, released the tensioner and spun one of the blades 90 to see if maybe they were each timed just right to cause the vibration (there is only 2 blades). This may have helped a little, but not much. I would think that a blade that is not balanced would cause constant vibration, not a cyclical rhythm.

[apbling 0]

I'd like to also mention, the vibration is worse in the thicker grass - in the more thin spots of my lawn the vibration was closer to not noticeable.

[BLT 718]

First question, is your belt tensioner free and doing its job? They tend to sieze up and the drive belt gets sloppy. When running the tensioner is real active.

[steve-wis 637]

Also, you say you ate the old belt. I would check the pulleys and make sure there is not a pc. of old belt or some buildup on them. The other thought I have is that it may take a bit of running for the new belt to be "broken in". New belts are stiff and sometimes need to run for a bit to work out the stiffness.

Steve

[apbling 0]

Thanks for the reply guys. I thought about this more last night and did some more internet searching and see guys talking about this issue, but noone has mentioned a rhythm to their vibrations - I see stuff in the pulleys, bent spindles, blades etc.

Earlier this year I did sharpen my blades some, didn't balance them because they are at end of life anyway. After re-installing them, I could occasionally smell a little belt burning - I thought this was odd, because all I did was sharpen the blades. It didn't do it that often, maybe 3 times since May and I cut my 1 acre weekly.

Also, the old belt - it was cracked and old and potentially the original even. Also, I guess I should have been more clear on eating it - it didn't break in 1 place, but two, and pretty clean break. One piece was maybe 6" long and the rest of it was intact. No big messy fray. Odd part is, no vibration with the old one, and I'm thinking maybe it's always been there, but was maybe so stretched and sloppy it was dampened out some?

As for the tensioner, it released freely and spun nice. I spun each spindle and it was free, but when I applied the tensioner, one of the spindles did make a little dry scraping noise, but nothing out of this world.

Also, I never thought the new belt might be stiff - the old one appeared to be black rubber. The new one ($51 later!) is white and I'm told its Brigg's new kevlar belt. It was coiled up pretty tightly too, so maybe that is my issue - it did seem to get better the more I cut... I'm a little embarrassed by the lack of maintenance this poor mower has gotten, but this thing is seriously a champ. My folks cut their 3 acre lawn for about 15 years with it before giving it to me and other than just maintenance, it keeps going and going.

[MikeES 458]

It could just be a bad belt, I have had a similar rhythmic noise on my drive belt and could watch the idler/clutch pulley move in this same rhythm. I changed belts and everything is fine. I think the belt had a flaw (not that I could see), like one section maybe a little bit narrower than rest of the belt.

BTW, it was not a simplicity belt.

Also check the deck pulleys to see if one has opened up on one side (flanges spread apart), which would act like an egg shaped pulley to the belt.

[Brettw 1,134]

but when I applied the tensioner, one of the spindles did make a little dry scraping noise, but nothing out of this world.

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Maybe it's me, but that is a fair amount of sharpening. I maybe sharpen mine once a season. Unless you have a blade balancer and a very good grinding system, with that much sharpening it is likely a blade is out of balance.

[apbling 0]

BrettW - I should have been more clear - I sharpened my blades 1 time, early in May. I did it with a super highly calibrated eye and benchtop grinder (so, really, not good at all haha). I had smelt some belt burning after the sharpening, but only a handful of times.

[johnmonkey 4]

...for the next belt (if it breaks)...after the failure, carefully check the temperatures of the tensioner, bearing housings and any other pulleys. If anything is too hot after a short run, then that could lead to the problem. I've also removed the deck and all the belts to free spin everything...if there is any grinding noise = replace. Good luck. JH

[apbling 0]

Ok, had some time last night to inspect. Took the belt off and examined it - I thought I had what looked like a little kink or something - then I realized the part that looked odd was there from how it was coiled up from the dealer. I could EASILY just twist my hands in opposite directions and the belt folded up like a lawn chair to its original out of the package shape....So I am thinking this maybe is my source of vibration and hopefully it'll damped out as the belt wears and loses its "memory" of being in its package.

I also did free spin/inspect the spindles, tensioner and main pulley - all of them looked good. I fired up the mower and engaged the blades in my driveway and watched - the tensioner did bounce a little, but not much, and I do recall seeing some movement on that through the years, so I don't think its doing anything it hasn't for the past 15 years. If I apply pressure to the handle of the tensioner to pull the belt tighter, things did smooth out, so maybe that spring isn't as strong as it used to be as well, but overall it looks to be operating properly.

At this point, I'm going to replaced the blades anyway since they are near end of life and keep using it. I really think after cutting 1/2+ Acre (so, maybe 35 min) with the new belt and it still having this "memory" is a good indication that maybe is my problem. I'm hoping the belt will break in some more. I used to work at a retail store that carried Murray and MTD mowers and parts. The belts we carried weren't coiled in a 9" diameter coil like this one, but a larger diameter coil...

[lugnard 73]

It does sound like a belt thing and probably will subside or you will get used to it. You could pick up a green belt of the right size from say Napa or the like or even just a regular belt and try that to see if it changes or goes away. Then put the "good" one back on and have a spare. I panic when I don't have at least one spare belt on the shelf!

Harry

[apbling 0]

Well guys, I took the ol' mower for a spin yesterday. Vibration was all but gone on the thinner/shorter areas of the lawn. Just the smallest vibration in the thicker stuff, especially when I was going too fast. I think I'm also in need of new blades because in the ticker areas I'm leaving a few blade trails un-cut, unless I slow down (it's mainly in the spots when I'm turning). But, the good news is the vibration seems to be almost gone with use.

Thanks for the help!