Front Master Cylinder Problems and solution
Note: This is on a 2009 which has a different front master cylinder (more tear drop shaped than square box) than prior years although I have heard a lot of folks with those older bikes have upgraded with the 2009 master as the earlier master was sub-par. I do not know if this same master was retained for 2010 and later. YMMV but most masters operate on a similar principle.
A bit ago I developed an issue within the first five miles of every ride where the front brakes would begin dragging which would get rapidly worse requiring pulling over to the side of the road. It was infrequent and once cleared would not reoccur that day.
Clearing the issue was done by pulling the lever and letting it recoil on its own several times.
In checking things out I found brake fluid under the dust boot so I assumed that the cups on the master cylinder piston were faulty. I ordered new cups and just to be safe a new spring. I parked the bike for fear that the problem would get worse and I decided it was likely dangerous.
Then life got too busy and I was out of town a lot so the bike remained parked for a couple months. In the mean time I decided to replace my lines with braided steel (HEL).
Finally, at long last, today I got time to tear into things. Sure enough the action of the piston when manually manipulated without the additional force of the brake lever was not good.
Replaced both cups (hint: spring clip pliers work great to stretch the 2nd cup over the piston) and the spring. If the spring and first cup are stuck in the cylinder, a tiny bit of compressed air down the supply port with a rag over the banjo bolt hole will pop those right out. Careful or they will depart for another dimension.
Flushed everything, swapped in the new lines and started bleeding. After a LOT of bleeding and not really getting any additional air I still had no brake "feel" at the lever. I pulled the master back off and consulted the service manual wherein it states that if the relief port is plugged the front brakes will drag. Well DUH! Wish I had seen that note a couple months ago!
The relief port (which is only a couple thousandths in diameter) was almost not visible. I finally found it and blew it open with the needle nozzle on my compressor. There was a lot of gunk blown into the piston space so I had to clean all that up (a .50 cal cloth patch on a cleaning jag works great). After all that I reassembled and poured in some fluid. Activating the lever caused a lot of air to come up through both the supply port and the relief port so I kept working it and tapping the banjo bolt until no more air came up. I almost immediately had a good firm resistance at the lever. Bled everything one more time just to be sure.
While chasing the air out I was using a similar technique to what cleared the problem when on the road and noted that this caused fluid (and air) to jet out the relief hole. So, I surmise that when I cleared the problem I was blowing enough junk out of the hole to allow the brakes to function normally then over night the gunk would settle back and occlude the hole.
This was on the original brake fluid (2009) so bad on me. This fluid was badly discolored with lots of floating gunk.
So, if its been awhile since you flushed your brakes with new fluid you might want to do that before Winter and while you are at it, check the relief port. I got lucking in that this never happened leaned over in a curve. Otherwise, it could have been disastrous.
Only had time for a short ride tonight but the brakes feel entirely different due to the new lines and didn't get any drag as before.
I think flushing the brake system is going to become an annual spring ritual here. I already bleed the brakes after Winter and it only takes a couple minutes to flush and bleed (with a vacuum pump...I have done it the other way, once, never again).
Sorry I didn't take any pictures. I was in "solve it mode" and not thinking about documenting the adventure.
2009 Kawasaki Versys
SWM Engine Guard; Windscreen de Jour on a MadStad bracket; Motowerk Peg Lowering kit & Stand Big Foot; ProTaper ATV Low bars; Stebel horn; KTM Duals Rear Rack; Coocase 36L topcase...and more to come
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