(quoted from post at 23:14:27 08/01/21) We went to see the machine. Overall in pretty good condition.
1. One of the large idle wheels was damaged on the inside edge. Initial thought was rot from sitting a long time but it could have been rocks.
Is this normal. Is it a huge problem? For us as hobbyists if the machine is 60% worn out it will still last a lifetime.
2. The tracks are very smooth. No cleats at all. Is this a certain type of track? Would it impact its traction significantly ? Would this make it impossible to move in snow?
Bill
Damage to the idler is likely from impact after being worn thin. Is it normal, yes it can be, if worn out and/or has seen impacts. The idler should be replaced.
The pads (plates on the track chains) are worn smooth. That is a sign of high wear. Depending on the type they were there should be 1 tall grouser (on a dozer) or three short ones (loader use). The grousers are like tread on tires, no tread, no traction. Most likely it would have poor performance in snow. It might move it self but forget pushing or pulling anything.
Yes, an undercarriage at 60% would last a hobbyist a long time. Sight unseen, from your description and questions here, I would say the undercarriage is not at 60%, but well beyond 100% worn out, and then some. Did you read the article on undercarriage I posted the link to for you? Did you measure anything or just eyeball it? Without making the proper measurements and comparing those to the manufacturer's specs, your percentage number is just a number you, or a someone, chooses to think it is. It has no verifiable basis to establish the actual percent worn.
The parts, like idlers can be replaced, there are some used ones out there, that may be better than the ones on it, but they will be worn for the most part. Like anything once and a while, a NOS one may turn up, but that is rare. You can contact Lavoy, at the link he gave you, he may have the parts you would need, he works on those crawlers.
New 420 undercarriage parts are pretty much NLA. If you wanted to renew it the fix is to go to 350 undercarriage parts for idlers, rolls, chains and pads. The 350 sprocket rims have to be cut off, fitted and weld to the 420 sprockets after those rims have been removed. A proper undercarriage renewal could be in the $5000 range.
Sorry if some of this sounds harsh, but your description says worn out undercarriage to me. They are good little crawlers and can be fun. They can also be money pits, look with your eyes open.