Bad VR?
 

I can hear air being forced out of the caps on the battery on my 102, does that mean my voltage regulator isn't working? Or would there be another reason for the battery overheating?

It's probably overcharging. Put a voltmeter across the battery terminals with the engine running. Anything more than 13.5V or so means the regulator is malfunctioning or out of adjustment.

I don't have a volt meter, I can borrow one though. I do have a spare VR, should I try swapping them out to see if that fixes the problem?

I would do as Matt suggested. Obtain a good quality DVM and measure the voltage. That will tell for sure.

There's no excuse for not having a multimeter when Harbor Freight usually has them on sale for $2.99. It's a tool you need to have if you are going to be working on one of these machines.

Had a nice $80 one from one of my electrical engineering classes, decided to sell it when the beer fund got low! I find a test light works for 99% of the time, this case being the 1%.

If no harbor frieght is close most parts stores have bargan bins with cheap meters in them.

In my world, I have found the higher the price of the meter, the better accuracy and durability. IMHO, that a good meter starts at about $50.00 and goes up. I once bought a $10.00 cheapy and I got exactly what I paid for. A piece of Chinese junk and after a few uses, threw it away. No accuracy, cheap case, and cheezy test leads. In my line of work, I use meters (Fluke) that run $200.00 and better.

That's probably true, but for measuring battery voltage, checking for continuity, etc, they work just fine. I have two of them; one at home for checking stuff on the Cubs and one down here in FL for troubleshooting cars appliances. My only complaint about them is the data sample rate is glacially slow.

Voltage was reading high so I switched out the V/R and all seems to be working fine.