Vic gives good info. You might also do a search here for "water cooled regulators" . The cooling system has to be well maintained -- personally would not run on muffs, but others might see that differently. Look for signs of overheating on your rectifier/regulator. It's an expensive little puppy to replace, so worth finding all the info. you can. Believe the R/R will be the problem for charging and tach operation (think you should see 14.2 amps at about 2000 rpm if the system is working, but check threads for info.)