Looking at a 1984 Jd 490

[animalv]

hello I'm looking at a Jd 490 excavator what should I look for. How hard to add a thumb.

 

[JDCrow]

Lots of threads to be found here on adding a thumb.

Extra valve, plumbing, wiring, thumb, welding. It gets expensive fast.

Personally, I would keep looking for a machine with a thumb. To me big savings in the long run.

 

[mitch504]

Cost of adding thumb depends on your skills and whether you need hydraulics or not. Most thumbs around here are manual.

I used some worn out tree shear blades, (7/8 AR500) and built my thumbs. I probably have $200 US, and 15hrs labor in each of mine.

 

[JDCrow]

ahh manual thumbs. They are almost non-existent here in PNW. Thanks for reminder

 

[mitch504]

When built the one on my 215c, I built it to be hydraulic. The machine was even plumbed for it, all the way to the stick. All I needed was the cylinder and 2 short hoses. Once I started running it, I never got around to finishing it. I can adjust it to 3 different angles, or fold it out of the way by myself in 5 minutes.

 

[animalv]

Yes adding a thumb can get expensive. I'm a heavy duty mechanic. I can do the hydraulics. I will get our fab guys to do the welding. mitch504 AR500 I wasn't even thinking of that, we have some laying around. I guess my main concern is this a half decent machine or do they have issues.

 

[JDCrow]

Father in law has a JD 490d that has around 20k hours. (No joke) he bought it new in 1988 I believe.

It ran hammer exclusively for last 15 years. Had its fair share of boom cracks, but it starts every time and will run all day. Slow compared to today’s machines, but it’s almost indestructible

 

[animalv]

wow lots of hours cracks in boom on this one they put fish plates on each side of the dipper stick up by the cylinder. this one has 8700 hours

 

[JDCrow]

From what I’ve read, booms cracks are the norm on these machines.

 

[excavator]

Probably the biggest issue with the 490D is weak final drives and having one go out will total the machine. Almost impossible to find and the few that are out there are usually priced at half the value of the machine. Around the Langley area I would think you should be able to find a good used thumb fairly easily and plumbing on those machines is fairly straight forward.

 

[skyking1]

It's kind of funny, I want to lose my thumb more than half the time, and you want one.

 

[JDCrow]

It's kind of funny, I want to lose my thumb more than half the time, and you want one.

Could never lose the thumb. Now if a tilt rotator fell in my lap, hmmmm

 

[skyking1]

I spend no small amount of time in trench boxes, and the thumb just sucks for that.

 

[JDCrow]

Ahhh. Yeah wide thumbs that go with wide buckets. The 120 I just got has a “small” thumb. Made for the 24” bucket and it narrows down to just 2 tines, kinda a triangle shape.

But you are right, if you are in loose earth and pulling boxes, a wide thumb would suck. When laying sewer here, it’s all shot rock, some hammering around utilities. So our trenches get really big and wide and shot rock just comes out as it wants too; thumbs don’t get in the way as much

 

[skyking1]

yep it's a 4 tooth thumb, but the big downer is the frankenstein ears stick out past the 24" bucket and it is impossible to keep the end plate on the pin.

 

[lantraxco]

As I recall the 490 is an EX120? You got Langley Excavator there in Surrey, those guys have always been real helpful to me, you might give them a jingle.

 

[Mother Deuce]

Home being the PNW and after working for years with PSM, Highline, Young, Pierce and Jewell compound thumbs that roll out flat with the bucket and finding myself
in the thumb wasteland that is New England... It makes me smile to think of a properly set up thumb with Cat pistol grips for demolition, clearing, stacking and loading.
I am fortunate that the company I work for here, keeps a 300 with a hydraulic thumb. The tradition here, as mitch pointed out leans toward manual thumbs. They work
and they are cheap but are limited in their reach and ability by comparison. Most of the hydraulic thumbs here lack the compound linkage and the cylinder is pinned directly
to the thumb pad. This is dramatically better than manual however it still is unable to roll out with the bucket through its arc. Also the cylinder is exposed to any side load
the pad may endure through either operator error/abuse, thumb pad distortion when closing due to improper design or fabricated out of material not up to the task and
pin and or bushing wear allowing movement of the pad as it closes. In my experience with this set up if you are careful and keep an eye on the thumb for twisting load it
will work for you. skyking1 has a point that if your slugging utilities in, the thumb is probably in the way. Good Luck which ever way you go. There seems to be a plethora
of machines available in the neighborhood that are already tooled up with a PNW thumb and matched bucket. Leave the breaker on the 490... in Redmond you will probably need it!

 

[animalv]

Looked at it yesterday she needs a little work besides bubbles in the rad when running probably head gasket, are these engines prone to this or cracked heads? Cyl 1 runs at 87F 2 & 3 180F cyl 4 140F possibly injectors. I put an offer in but a lot lower then asking price. Other then low on power to walk you would think fix hydraulic leaks, fix up bucket and good to go.

 

[JDCrow]

Looked at it yesterday she needs a little work besides bubbles in the rad when running probably head gasket, are these engines prone to this or cracked heads? Cyl 1 runs at 87F 2 & 3 180F cyl 4 140F possibly injectors. I put an offer in but a lot lower then asking price. Other then low on power to walk you would think fix hydraulic leaks, fix up bucket and good to go.

The engine is simple enough, not sure if it’s a lined engine. Like I mentioned, the 490D has been solid. It’s the main reason I bought the EX120 I did, solid with good part support still. It’s a great sized machine. As long as you are happy with the price and built in yourself some money to wrinkle out some costs

 

[lantraxco]

Probably need to reseal (or rebuild) the swivel joint, that's usually the culprit for low track power.