GCK60-BX loves to eat shear bolts. Any ideas?

[MDL]

I have about 16 hours on a GCK60-BX grass catcher and have already been through 3 shear bolts. There are two shear bolts in this unit, one at each end of the blower unit's driveshaft which runs between the grass catcher's two gearboxes. The shear bolt on the power side keeps breaking.

I mowed with the tractor the first 2 times with no problems. The third time I mowed the first shear bolt snapped. I figured it was operator error and I had overloaded the discharge chute with some heavy or longer grass. The shear bolt was replaced and all was well. The fourth time mowing I decided to use a slower travel speed and make narrower mowing passes in order to keep the amount of cut grass going up the discharge chute down. I got about half way through the lawn (about 1 acre) and ZING there goes another shear bolt. Funny thing was I was passing over an already cut area of the lawn. So, I replaced busted shear bolt #2 and finished the lawn. I went out yesterday just to dress up the lawn, which had recently been cut, and got about 1/2 way through.....ZING! Shear bolt #3 went to the big bolt pile in the sky. I'm about to put a hardened bolt in that driveline because I'm frustrated but I know the shear bolt is there to protect the blower's gearboxes and the tractor PTO. I can't imagine Kubota meant for the shear bolt to be replaced before each mowing. So, I reach out to the wealth of knowledge here in TractorByNet-land as ask for your thoughts, ideas, and so on.

Something else I want to add....yes, the discharge tube from the deck to the blower was clear as was the deck's boot. The grass bags were only 1/3 full. I operate the tractor at about 80% throtle (I go full throttle and just bump it back a tad because the tractor is still on break in hours). It's always the same shear bolt that fails.

Help!

 

[stevenw]

I have the same bagger and I have about 32 hours on it now. I have never broken a shear pin. Are you engaging the PTO with the idle all the way down? That's what they recommended. I have clogged it with thick grass twice and still haven't sheared a pin. I would recommend you contact the dealer and have them check the bearings, gear box etc...something may be binding up. Did you check the gear lube in the unit? Troubleshooting while I'm typing. I also run mine at about 2700-2800 RPM's 2/3 throttle.

Steve

 

[JWE]

I have the same catcher and have never sheared a bolt in about 8 hours of operation.

I engage the PTO at or under 2000 RPMs and mow at 3100 RPMs.

John

 

[MDL]

I'm thinking that one of the gear boxes has a bad bearing or other such problem which causes it to heat up and then cause enough resistance to make the shear bolt give way. I noticed the impeller side gear box has some oil blow by past the drain plug. I can't imagine I'm doing anything wrong at this point so its time to get the dealer involved in some real trouble shooting or parts swapping.

Thanks for the sanity check guys.

 

[brinet]

I have about 370 hours on my tractor, BX2200 (about half with the bagger) with only one shear bolt problem. This was due to running over a stick and the stick JAMMED the chute and impeller fan. The shear bolt was cheap to replace. The cheap plastic impeller fan was $80!

BTW, does your impeller make a very annoying low pitched noise? Even with ear protection it is VERY LOUD!

 

[noreault]

Mine is on its third season. I have had a pretty consistent problem with the shear pin about every 10 to 12 hours of use. Putting on ideal to engage seems to help, but it does shear without a heavy load. BTW, there are two bolt on the drive shaft between the gear box and the fan that is inside the case. I managed to shear one of those. A real pain to change. I did put a hardened bolt on that one, but wouldn't think of it on the regular shear bolt.