How much force should be needed to get the backhoe unhooked? I'm pulling back pretty hard on 180 in the picture, but 070 isn't lifting at all, and I'm wondering if that's normal or I'm misunderstanding the mechanism.
If I am understanding correctly.....that is the boom lock for transport purposes. Because the boom cylinder will slowly bleed off (hydraulically) over time. when it does this, you have the whole weight of the backhoe being held by them hooks.
Fire it up......raise boom all the way....and it should go pretty easy.
Not familiar with the M59 though, only the smaller kubota backhoe attachments, in which the boom locks have a detent of sorts where you have to pull OUT and back on the lever. Then it rests in another "detent" to hold it in the "released" position.
On my BH92 it takes no effort at all to pull that lever back. As others said you must pull the boom back first and you will notice the pin that sits against the mechanism that holds the boom back about 1/2”. Then it should release with no effort at all, like you can do it with your pinky finger easy.
I use to have to use the right stick to bang the boom to be able to release the lock. There was a recall on the cylinder, something about the internal cushion kept it from bottoming out enough to unlock. I had it done, they replaced the cylinder.. might check with dealer.
How much force should be needed to get the backhoe unhooked? I'm pulling back pretty hard on 180 in the picture, but 070 isn't lifting at all, and I'm wondering if that's normal or I'm misunderstanding the mechanism.
Once #170 is clear of the latch pin it lifts easily.
You need to raise the boom all the way for the catch on #170 to clear the pin its grabbing onto. If the pin is clear then your catch #170 isn't rotating on its pin and is likely seized. Get out the penetrating oil and let it soak several hours before using a hammer and a block of wood to tap and free the rotation on #170.
Once you get #170 moving I'd pull the pin on #170 to thoroughly clean it and the bore. Use lots of anti-seize when re-assembling it.
WD40 isn't really the best penetrating oil its more like duct tape when you need vise grips.
I'll try moving the boom a bit after work and see if that was just putting it under tension too much. I just got the thing, so I haven't got a feel for it yet. Next challenge will be removing the backhoe and hooking up the top and tilt. I should order some gloves.
Is it bad to let the boom bleed down when parked? Assuming the bucket isn't rusting in a puddle, is it necessary to lock the boom after use?
Is it better to run the engine at low or high RPM for light backhoe use? Like is it better for the life of the hydraulics to run at a certain speed or does it not matter and it's more about responsiveness vs fuel consumption?
Run the engine as fast as needed to get the speed needed out of the hoe. Any faster & it burns more fuel & makes the hoe twitchy & jerky because it's going faster than you are.
The hydraulics aren't going to care really unless you hit relief a lot if your pump has a bit of internal leakage (they all do to some degree) you might need some extra RPMs to overcome that & get maximum hydraulic power. If the engine is a tier 4 with a diesel particulate filter it will a little. A DPF works much better at mid to high RPMs. Low engine RPMs & bogging the engine create more soot. And more soot means more filter clogging & more frequent regens. Not the end of the world as regens are there to clean & regenerate the filter. But best to kick up the RPMs some & minimize the wear.