Slow Monster rebuild

350TSS · 23-06-2020, 03:09 AM

I have been putting off today because I hate working with brake fluid especially when you have finished parts either painted or awaiting painting. The plan was to spend about 3 hours bleeding the clutch, the front brakes and the rear brake.
I started with the clutch, nipped up the banjos, filled the master cylinder and pumped the lever slackening and tightening the bleed nipple above the banjo on the slave cylinder. After 20 minutes no more air appearing so all seemed good.
I then tried the clutch action, permissable free play, then like hitting a brick wall, an absolutely solid lever, no disengagement of the pressure plate. nothing. WTF.
My first thought was that the problem had to do with the alternator case which I previously cracked and had to have welded and the hole for the clutch push rod had to be re-drilled and one of the clutch slave cylinder attachment threads had to be re-tapped. Perhaps it was all misaligned and causing the issue. The slave was removed and the pushrod was free to move. Maybe I had misassembled the clutch itself, so the pressure plate came off and the plates and the hub were taken off and re-assembed. All was fine at that end of the pushrod.
Suspicion then fell on the Chinese slave cylinder so I swapped it for one off the S4 parts bike I bought which I knew worked. But that meant cleaning it up and re-bleeding with the new slave.
The result was the same. A completely solid lever. WTF.
The clutch master cylindeer is definitely pumping fluid, the clutch pipe is definitely delivering fluid, the slave banjo is passing fluid to the bleed nipple above. The banjo /bleed nipple came off the aforementioned S4 mongrel and worked there but, for some reason, in both a brand new Chinese slave and a previously perfectly functioning S4 slave the pistons are not transmitting hydraulic drive to the push rod. My only thought was that the pistons in both cylinders were too far withdrawn and that somehow the piston skirt was blocking the entry port for the brake fluid to get into the cylinder and behind the piston.
Stumped, I left a bungee cord applying pressure to the lever to see if magicallly, overnight the problem would disappear.

23-06-2020, 03:09 AM	#11
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	I have been putting off today because I hate working with brake fluid especially when you have finished parts either painted or awaiting painting. The plan was to spend about 3 hours bleeding the clutch, the front brakes and the rear brake. I started with the clutch, nipped up the banjos, filled the master cylinder and pumped the lever slackening and tightening the bleed nipple above the banjo on the slave cylinder. After 20 minutes no more air appearing so all seemed good. I then tried the clutch action, permissable free play, then like hitting a brick wall, an absolutely solid lever, no disengagement of the pressure plate. nothing. WTF. My first thought was that the problem had to do with the alternator case which I previously cracked and had to have welded and the hole for the clutch push rod had to be re-drilled and one of the clutch slave cylinder attachment threads had to be re-tapped. Perhaps it was all misaligned and causing the issue. The slave was removed and the pushrod was free to move. Maybe I had misassembled the clutch itself, so the pressure plate came off and the plates and the hub were taken off and re-assembed. All was fine at that end of the pushrod. Suspicion then fell on the Chinese slave cylinder so I swapped it for one off the S4 parts bike I bought which I knew worked. But that meant cleaning it up and re-bleeding with the new slave. The result was the same. A completely solid lever. WTF. The clutch master cylindeer is definitely pumping fluid, the clutch pipe is definitely delivering fluid, the slave banjo is passing fluid to the bleed nipple above. The banjo /bleed nipple came off the aforementioned S4 mongrel and worked there but, for some reason, in both a brand new Chinese slave and a previously perfectly functioning S4 slave the pistons are not transmitting hydraulic drive to the push rod. My only thought was that the pistons in both cylinders were too far withdrawn and that somehow the piston skirt was blocking the entry port for the brake fluid to get into the cylinder and behind the piston. Stumped, I left a bungee cord applying pressure to the lever to see if magicallly, overnight the problem would disappear. Last edited by 350TSS; 23-06-2020 at 04:08 AM..