The Big Twins
We now see Twins out of India as large as 28 horse power!
Most of these large twins make their rated power at 1000 RPMs. As you might guess, the flywheels are smaller in diameter to stay within the rim speed limits of cast iron.
To date, I have heard of 10/2s 12/2s 16/2s, 20/2s 24/2s 25/2s and 28/2s
Most of the engines 20hp or more are making their rated power at 1000 RPMs, but expect to see all kinds of things as everyone is building a variant.
When you get into these engines, it is important to note the vendor and even the serial number before you order parts! Following is an example of the center support bearings we have come across so far!
Above: Center Main support bearings
You can see all of these are different! If you have a "big Twin"; you can't just expect to get a standard bearing because they are different! As you might notice, the Ashwamegh bearing is used, Scott Emery brought this one over so we could photograph the three difference sizes we have discovered thus far. I was hoping we could use the Jkson bearings as I have found that Ashwamegh offers some pretty poor support for their products, (to their dealers anyway), but fact is, if the engine was properly prepped and clean, these bearing should last for a long time. The Ashwamegh bearing is full of sand, and it appears that the Ashwamegh employee responsible for cleaning the sand out of the case was on holiday when this engine was built.
I have yet to hear of a twin racking up the hours that a 6/1 does, 6/1s seem to run forever and can be rebuilt in minutes, but the big twins, I'm still waiting to hear about one running for the long term. Since they are new, it may take a while to build their reputations..