Brake Fluid

For clarity, my '05 HD is the only one I've seen with DOT 5 specified. My '91 and my '07 both spec'd DOT 4. Only a guess, but it may have been tried for one or more years to get away from paint damage, fit and finish being so important to their owners. The company may have gone back to 4 due to inadvertent cross-contamination by their dealership mechanics. I found no detectable difference in brake performance after flushing the 4 and moving to the 5.

"I suspect that if Norton used cast iron they would have specified DOT 5 fluid."

But, of course, there was no such thing as DOT 5 back then...or DOT 4, for that matter. DOT 3 was it. And really, did anybody have trouble with it?

Trouble...only when it leaked out and hit the paint.

Im going to risk the 5.1 and see how it goes. Ill
keep a close eye on it and if it leaks will just have
to muscle up and do a rebuild.