Brake Fluid

[jt03rubicon]

For a 1980 with stock front disc brake, the owners manual recommends using SAE J1703B brake fluid. Is this equivalent to DOT 3 or 5?

Thanks for the help.

 

[PrinceJ57]

Pretty sure that's DOT 3

 

[Tomterrific]

DOT 3 but the easiest to find is DOT3/4 which satisfies both the 3 and the higher 4.

I strongly suggest you flush the system with new fluid by pumping the brake lever while using the caliper nipple as a valve. Keep the new fluid flowing until it comes out clear at the caliper. Do another flush in about a month because the new brake fluid will pull contaminates from every nook and cranny and get dark again.

Tom

 

[Gordon]

On the cover (master cylinder) of my '80 states to use DOT3. 3 &4 are pretty much the same, 4 has a higher boiling point, but same chemically. DOT 5 is a silicone based fluid, not compatable with DOT3-4 rubber part's. My Harley takes DOT 5, tried to use 3, swelled every rubber part to the point of locking the brake.

 

[jt03rubicon]

Yeah, using a DNA master cylinder...I will go with DOT 3.

Thanks for all the help.

 

[jayel]

On the cover (master cylinder) of my '80 states to use DOT3. 3 &4 are pretty much the same, 4 has a higher boiling point, but same chemically. DOT 5 is a silicone based fluid, not compatable with DOT3-4 rubber part's.

My Harley takes DOT 5, tried to use 3, swelled every rubber part to the point of locking the brake.

that is Dot 5 rubber parts not compatable with Dot 3 fluid, not Dot 3 parts not compatable with Dot 5 but you should use what is recomended but you all ready know that

 

[jt03rubicon]

Ok, so my my master cylinder is a GMA and the manufacturer recommends Dot 5 brake fluid. Now, to make this build economical, I would like to use the stock 1980 brake caliper.

Will this set-up work using DOT 5 fluid?

 

[jayel]

I would say you need to do some reading and research
http://search.avg.com/?d=4dd6f5e6&i=23&tp=chrome&q=using+dot+5+in+place+of+dot+3&lng=en-us&nt=1
but maybe if you ask MMM at ( http://www.650central.com/ )he could give you the best anwser, the best brake guy on the forums

 

[5twins]

Yes, the Yamaha brake components are compatible with DOT5 but you must thoroughly clean the DOT3 or 4 out first. That usually involves flushing the component or disassembling and cleaning it with alcohol. In your case, I would recommend a disassembly of the caliper. These bikes are so old that the brake components are usually all crusty inside with dried up brake fluid residue. Flushing isn't going to get that crust out and it's DOT3 based crust. That's why I think you should take it apart.

 

[Gordon]

I agree with 5Twins, but go a step further, rebuild the caliper with new seal's. The silicone fluid is absolutly NOT compatable AT ALL with the glycol based fluid's. A rebuild kit is not a whole lot of money, and with the new seals the system should be pretty clean. To flush out the line's, you can use warm soapy water, then clean water to flush out the soap. Blow dry with compressed air, and the lines should be good to go. I have a GMA on the bike that I tried to use DOT 3, won't work.

 

[jt03rubicon]

Thanks for all the help! One step closer to getting this thing on the road.