Hello Gentlemen I’m looking for all the help I can get and your expertise I’m looking at. 1961 d6 the guy is asking 6k for it says it was recently rebuilt by cat but he has no paperwork it looks rough but I’m hoping this is just cosmetic the good thing is it only about 20 miles from my place in Michigan your options are greatly appreciated thanx Scott  

This machine is a D6B SERIE 44A with d333 motor

dose it still have a pony start? as most d6B had a new style pony that where know as buzz bombs. they cam apart a lot of the time I think they ran 5000. lest just say parts are not very common

If it was recently rebuilt by a dealer, ask what dealer did it and take the serial number and sellers name and they will probably verify if it actually was rebuilt. Nothing looks fresh on that neglected beast.

Hello Scott, That D6B seems to be a fair deal at that price. I don't think anything has been done to the engine for a long time. If the tractor operates and turns okay see if he will move it to your place for you or if he will take a little less.
Look at the amp gauge and see if is showing charging after starting the engine. If it isn't you will have to convert it to a 24V alternator in the future as the 24V generator is no longer available. If you try to have the generator rebuilt please note that the pully nut must be torqued to no more than 30 ft. lbs. as that preloads the generator bearings. If the nut is over-tightened the generator will have a catastrophic failure after only a few hours of operation(Ask me how I know!!) The generator must also be "polarized" before use.
You should only use AW32 10W oil in the hydraulic system, 
The most important thing for you to do is become a "paying" member of ACMOC. This will allow you to access the ACMOC library. The library contains all the books on the basic D6B, the hydraulic system and the blade. The Operation and Maintenance Instructions(OMI) is the most important manual to read before you operate the tractor.
This D6B is equipped with direct electric start.
The D6B "Buzz-Bomb" starting engine actually spun to 6,000 RPM when the throttle was set to "high-idle" to start the diesel engine!
Good Luck!
Craig

 

Get a kick out of all the ' Cat 'exspurts "and their old wife's tales.
That starting motor never was supposed to turn over 5050 RPMs on fast idle, most were set at 4000 RPMs.on other motors.
In any case I would say a motor that may be 60 years old that still works can't be all bad.
Bob

Okay Bob, I might have misremembered the story of the buzz-bomb starting engine that original owner of my D6B told me about the starting engine when the tractor was new.  He lives in New York State and said the first starting engine got it's oil from the diesel engines crankcase. The little engine had to run without oil until it could raise oil all the way up from the diesel engines crankcase. He said the first starting didn't last very long. He told me Caterpillar's solution was to add an oil pan to the starting engine. That solution made second engine last longer but it failed too. The modification to the front belly pan to make room for the new starting engine's oil pan can still be seen on my D6B. He then converted the tractor to direct electric start.  In any case, that high RPM starting engine was a failure. To see how big a failure it really was read pages 25-27 of the memoirs of Caterpillar Tractor Co. Service Representative Merv Rennich "Beer and Diesel Fuel." 
I included a true story about Caterpillar's Delco 24V generator's pulley to illustrate how easy it's to make a costly error due to lack of information. It caused me to buy a new generator, generator pulley, fan and belt set back in 1979. 
Craig
 

Hello Scott, After I looked at your photos again I noticed that the left track adjuster must have failed and is now being held in place by a block of wood. That should be fixed if you buy it.
Craig

 

There are more questions than answers on evaluating a tractor by picture. The blade itself says used and used hard. But no other big signs of big time abuse show right off. One thing I see in the same picture as the spacer block in the track adjustments shows the best in, right above the front carrier roller track looks to not be flexing. But looking in person is the only way to know for sure, a real guess from a picture. Which is good in it generally indicates more life left in the rails and pins and bushings. But a pain to fix. But track adjustment looks out to the end, not good. So look at pins and bushings to see how out of round they are.

What do you know about the operation of the earlier Cat's ? The release the steering clutch and apply brake to make turns. We need Sasquatch to do a you tube rather than explain it each time. But you cannot know if you don't get a chance to learn, so don't be afraid to ask more questions. But you may know a lot already, so not trying to put you down ether. If it turns and pushes ???????? Then worry about the paint.

The seller needs to do something more to prove any work has been done to that tractor. But on the other hand moving it 20 miles versus 200 miles adds up fast too. So check oil levels in transmission, final drives, hydraulics and the engine. My motto most days is a leaking final drive is one with oil in it, rather than being dry. But big leaks need fixing.