Low fluid pressure below 55 degrees

[SinisterMatti]

I recently replaced my front master cylinder with a Hughes Handbuild one and threw on a SS braided brake line for good measure. Everything works great during the day, but early in the morning when it's below 55 degrees F outside I have to pull the brake almost to the handgrip to get any stopping power. Later in the day after everything has warmed up the brake works perfectly. I never noticed this problem with the oem master cylinder and brake line. Any ideas why this is happening and if there's anything I can do to prevent it?

 

[pamcopete]

What type and brand of brake fluid did you use?

 

[retiredgentleman]

That's a very dangerous condition. I would remove that new M/C and put the stock M/C back on, before driving the bike again.

The stock M/C was made in Japan (Nissan I believe), and is a high quality unit.
These aftermarket sellers are selling a M/C made in China/Taiwan, for a low price, but guess what, they are low quality too.

These are brakes we're talking about, buy the best quality that you can, because your life may depend upon it.

When I wanted to change the size of the bore of my M/C, I bought a brand name that you may recognize (Brembo). Yes it cost about twice as much as the China/Taiwan units, but its safe and reliable, and worth every penny.

 

[650mark]

consider dumping that aftermarket stuff and put a rebuilt oem setup back on. fwiw, I've restored 5 xs650's now, including my current ride, all with original brake systems and I've never had a single failure or issue with any of them. I've rebuilt the m/c and the calipers with quality kits but again, never a problem after many thousands of miles. of course, ymmv... but get good brakes!

 

[SinisterMatti]

What could cause it to have lower pressure in the colder weather than the normal day though? I'm using the Yamaha brake fluid recommended for the bike.

 

[pamcopete]

What could cause it to have lower pressure in the colder weather than the normal day though? I'm using the Yamaha brake fluid recommended for the bike.

You may still have some air in the system which loses pressure with the cold air. Try bleeding the system again.

 

[retiredgentleman]

What could cause it to have lower pressure in the colder weather than the normal day though? I'm using the Yamaha brake fluid recommended for the bike.

Really cheap, poor quality rubber seal ring used on the M/C piston??

 

[SinisterMatti]

Really cheap, poor quality rubber seal ring used on the M/C piston??

My stock MC was a mess, and I'd rather not pay for another used one that's going to look like crap. What MC would you recommend? I see you said Brembo makes a good one?

 

[retiredgentleman]

My stock MC was a mess, and I'd rather not pay for another used one that's going to look like crap. What MC would you recommend? I see you said Brembo makes a good one?

I can only recommend what I have experience with.................that would be Brembo.

 

[SinisterMatti]

I can only recommend what I have experience with.................that would be Brembo.

I'm just trying to figure out what model others are going with. I went onto Brembo's site and according to them the only product they have that works with my 1978 XS650e is brake pads.

 

[retiredgentleman]

I'm just trying to figure out what model others are going with. I went onto Brembo's site and according to them the only product they have that works with my 1978 XS650e is brake pads.

I bought my Brembo M/C from www.bevelheaven.com.

 

[SinisterMatti]

So something like this? https://store.bevelheaven.com/Brake-Related-Parts/13mm-REC-Brembo-Master-Cylinder-Front-Brake/

 

[Punkskalar]

Aaron

I've never had that problem with them, I run them all year long on our personal bikes (my employee was riding in 30 degree weather 86 miles one way last year for a few weeks when his car was broken down)

Are you using Dot3 or Dot4 Fluid? If you have moisture/contamination in the fluid, it could be stiffer due to that. I would recommend a flush and new fluid. I have always run Synthetic fluid from a NEW bottle. Open containers will absorb moisture and cause issues as well.

Brewdude wrote an article a few years ago for The Horse, and recommended changing fluid every year for maximum performance - depending on how long you've had that system operational, it may be a good time to drain and re-bleed.

Let me know if you have any more issues, and If so, we'll replace it no questions asked.


Hugh