Track Coming Off KX91-2

davey4000 · Jun 21, 2011

I have an opportunity to buy a mini ex at a good price. The owner says one track will jump off in tight situations even though the tension bar has been maxed out and the track shortened. I know nothing about excavators. Is this an expensive fix?

Bob Rooks · Jun 21, 2011

Could be. Check the "toe in" on the track frames. Shouldn't be any at all. Also check idler tracking.

davey4000 · Jun 21, 2011

Thanks. I guess I'll be taking it to a shop if I decide to buy it. I don't know how to do either of the things you mentioned.

Bob Rooks · Jun 21, 2011

Just for a rough measurement mind you, measure the distance between the track frames at the first and last roller (not the roller itself). They should be the same give or take 1/4". If not, $$$$$$ to repair
For the idlers, lay a straight edge or a taught wire across them fore and aft. They should track true to the track frame. Not too expensive, probably a bent yoke, which is not uncommon.
If the drive sprockets are out, move on unless you are rich.

davey4000 · Jun 21, 2011

Thanks for the tips. I figure you already guessed I'm not rich or I'd be buying a new one!

Bob Rooks · Jun 22, 2011

davey4000 said:
Thanks for the tips. I figure you already guessed I'm not rich or I'd be buying a new one!

Ha ha. Believe me, I understand.:laughing:

Builder · Jul 4, 2011

Other "experts" here told me I was "crazy" or "drinking again", etc. when I told them one of the things I didn't like about my mini-ex is that it loses a track once in a while when going over rough terrain.
Guess I'm not the only one.....
Something could be bent, you might want to consider other units because it's a PITA to deal with. Especially when it's used to make money.

davey4000 · Jul 8, 2011

Well I took a leap of faith and bought the machine. I'm in the process of doing all the 2,000 hour maintenance before I start working with it. No, I'm not using it to make money. I'm getting ready to retire and use it on my farm. I guess I'll have time to fool with it and not worry about it costing me my livelihood.

I do have another question. Probably the first of many. The little round "window" or gauge as they call it, for observing the hydraulic fluid level is cloudy. If it's not cloudy the fluid level is above the window and a strange color. I will be changing the fluid and filters and was wondering if the gauge can be cleaned or should I replace it? It doesn't leak or anything. I suppose I can also check the fluid level with a clean dowel, which I haven't done yet.

Bob Rooks · Jul 8, 2011

Several things can cause hydraulic oil to look bad, and there is a reason for them:
1) Cloudy:
a) Whitish in color: water emulsification (can be combined
with a suction air leak).
b) Tan or yellowish: Areation: (can be combined with the
wrong oil that won't release entrained air fast
enough).

2) Color:
a) Charcoal (blackish): High presence of cast iron or steel.
Also, neoprene, rubber, or buna-n components breaking
down.
b) Dark brown / red: The oil has been toasted and fried,
usually accompanied by a pungent smell.

All of the above conditions require changing the oil and filters.

Builder · Jul 9, 2011

Although it's an expensive, I would suggest changing the fluids when buying any used equipment. One of the negotiating tools I use when buying used equipment is to have the seller pay to have the fluids changed as part of the deal. If this doesn't happen, I do it myself.
You'll feel better knowing all fluids have been changed and the proper fluids & filters installed anyway.