Is it really a bad idea to mix them or is that just legal gobblygook the manufacture tells you?
Long story short. Previous owner made it a point to tell me that my '83 Roadster takes ONLY dot 3 and that is what he put in it. It is clearly marked dot 5 on the master cylinder lid.
I have the rear master cylinder off of the bike. Will it be good enough to refill it with dot 5 and then bleed it out?

 

NO
You cannot mix DOT 3 and DOT 5. You cannot use one to purge the other out. Use only the type of fluid that is printed on top of the master cylinder cap. DOT 3 & 4 are NOT compatible with DOT 5.

 

What he said. Absolutely not. You must use the fluid required for your brake system.

 

better check with somebody at HD, don't think an 83 xl came with dot 5, might be a newer caliper.

 

It will eat up the rubber seals.

 

I'm thinking DOT5 was not invented in 1983. The previous owner probably replaced the lid and that is why he specifically told you to use DOT 3 and not DOT 5 that it says on the lid.

 

Check with previous owner about having replaced the cap. I believe piasspi is right.

 

Get a factory manual for your year Sporty. Or check the owners manual, and go by what the book says is supposed to be in there. Don't screw with your braking system, and don't take someones word for it, imho

 

nooooooooooooooooooooo!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!


dot 3 and dot 5 are NOT compatible! Your brake system will leak for EVER if you put in 5 when you should have put in 3. Double, triple, and quadruple check with the p/o about what he put in there to include showing you the bottle of brake fluid!!!!!!!

If you mess it up you will know it for sure!

 

Ok ok ok I can take a hint. You don't have to more than 4 or 5 times lol.
......going back out to the shop to check the front brake master cylinder and to consult with Mr. Clymer.