I have 3 Marlin Levermatic model 62s (30 Carbine Short throw lever) that consistently fail to extract military ball ammo.
I want to disassemble to check extractor spring tension or possibly work on and modify the extractors.
Is there a simple/pattial disassembly method that I can do where I would have access to the bolt and not have to take all the lever activation pieces apart. (I understand that this rifle has lots of springs and gears in it's lockwork)

I have a 57M that I am sure is same action. I replaced the barrel so I've had it apart several times and it is not a big deal to remove the bolt.

Like you, I have extraction difficulties with mine. I suspect it is because my extractors are either worn or improper (they are different than the illustrations on the Numrich site) and I've been meaning to disassemble it again and look closer. I'll try doing it in the next day or two (but apologies if I take longer as I have this magically appearing Christmas honeydo list that always seems to grow faster than I can get rid of it!).

You probably have this already, but here is the Numrich page with the exploded view:
http://www.gunpartscorp.com/ca...cts.aspx?catid=11773

I have both a 30 carbine and a 22 mag version of the levermatic. The trigger assemble and lever are enclosed unit. If I recall correctly there are two screws holding the front of the trigger group to the receiver and a pin with a screw on the left side going into the pin holding the rear of the trigger group. Remove the action from the stock pull the trigger group and the bolt comes out very easily. Reminds me a lot of taking apart a 10/22. Only real trouble I had was getting the action out of the stock. To be honest I don't remember how I did it. I think I had to pull the metal plate off the stock for the lever to clear or the lever had to be in a certain posisiton but I don't recall exactly.

There are numerous pins in the trigger group. But the side plates of the group are held in place with screws so there is no real worry of it self destructing. If there is any concern just cover both ends of the pins with tape prior to taking the trigger group out of the receiver.

I had extraction problems with my 22 mag. Some super fine steel wool wrapped around a cleaning brush on a short cleaning rod chucked in the drill cleaned up the chamber and polished it to mirror bright. Extraction problems are gone.

I got a couple of responses that helped, so I went ahead and experimented.
Bottom Line: YES, THERE IS A SIMPLE WAY TO PARTIALLY DISASSEMBLE.
The lockwork for the rifle is totally contained between two metal plates.
It is not necessary to totally disassemble to get access to the bolt, etc.

The lockwork and two metal plates are designed to stay together and to pivot down on a pin at the forward section of the assembly.
To release the assembly for pivoting, remove two screws which are just behind the pivot pin (a medium diameter pin at the front of the assembly) then remove the large screw at the rear of the assembly. Note: One of the rear screws is actually hollowed and tapped to accept the opposite side screw.
After the front and rear screws are removed, the whole lockwork will pivot down and allow access to the bolt and any other parts.

I found no problem with the 30 carbine chamber. I can see very slight reamer marks, but don't believe they are enough to cause extraction problems I am having, sinc ethe extraction problems occur with 3 different rifles.
The extractor has a strong spring and when a cartridge is in place, the extractor seems to fully and properly engage the extraction groove.
My belief is that when a case is hard to extract, the pressure on the extractor causes the extractor to release itself from the case.
Since the stuck case requires very litle force from a cleaning rod to free it, a small improvement in holding strength of the extractor may be sufficient to overcome sticky cases remaining in the chamber.
My thought is that the extractor could use a slight angle change so that it would "dig in" and be less likely to pull free when a case is hard to extract.
Anyone hav thoughts about this idea?
I plan to try and buy an extractor and do the mod to it, and not take a chance at ruining the factory extractor.

If you have three of these and all of them have extraction problems I would look into the ammo. As long as things are apart polishing the chamber would not hurt. The spent round should simply fall out of the chamber no tapping however light of cleaning rod should be needed.As for the extractor. Two things to try. Filing like your thinking for more engagement may help. Other thing to try is a heavier spring. Heavier spring might be a lot of trial error. Need heavier to grip the rim for extraction but not too heavy that it won't snap over the rim when chambering.