Morning people I recently upgraded the the front calipers on my rvf one of a cbr600rr all bleeding done no air in the system good solid lever but after about a week there's no pressure lever comes right back to the grip no leaks any ideas

What hoses have you got fitted? Did you refurb the master cylinder and is it the RVF one or CBR600rr one?

Are you absolutely certain there's no leaks?

Could be OEM hoses leeching air, bad banjo joint, knackered bleed nipple not sealing properly or knackered m/c seals.

Original brake lines rvf m/c and definitely no leaks

Original hoses will be at least 22 years old then. Maybe time to consider an upgrade? After such a period, even pristine looking hoses will be degraded inside. I replace OEM hoses after 5 years without question.

I'd also consider a master cylinder overhaul kit.

It sounds like you're either losing fluid somewhere or, more likely, there's air getting into the system.

It's only since I changed the calipers could it be a case that the m/c is not compatible with the bigger calipers or does it make a difference is a m/c a m/c

The size of the m/c will affect the amount of "power" in the system but that amount of "power" should remain constant. It doesn't explain the complete loss of "power" you're experiencing. What you describe says to me that there is a fault in the system.


Just one other thing - Have you checked the brake fluid level? On occasion you may need to top it up after the pads have bedded themselves in and the pistons have settled in their relaxed position.

Suspect you still have air in the system that is distributed throughout the system during use to give a "solid" lever and then collects at one point after a period of a week.

I find that brakes bleed better if:

the master cylinder is elevated to the highest point

the caliper pistons are forced fully back and

then pumped out to a point that represents fully worn brake pads (use a plate of metal to simulate the disc thickness) and

then fully compress the pistons again

repeat until there are no air bubbles returning to the master cylinder.

My suspicion is that insufficient fluid is forced through the system when using the conventional method of bleeding from the calipers.