Joined
·
311 Posts
Sam,StavesacredarK said:
You have either adjusted the plunger screw incorrectly or your new levers have pushed the plunger further into the master cylinder when they are at rest position.
There is a screw on the master cylinder (usually has some kind of seal on it to prevent people from adjusting it) that people incorrectly think it is the lever-to-bar adjustment screw. Although that screw affects the lever distance, it really is NOT a lever “adjustment” screw. As you have found out, you had blocked the master cylinder bleed hole by either screwing in that screw too far, or adjusting your new lever distance at rest position incorrectly.
When the lever is at rest position (NOT pulled-in) the master cylinder seal (i.e. plunger) should rest behind the bleed hole, allowing the fluid to expand back to the reservoir when the fluid expands from the heat from the brake calipers or when atmospheric pressure out side increases.
By screwing in that screw too far you have basically forced the plunger to sit in front of the bleed hole at rest position. With the plunger resting in front of the bleed hole when the brake fluid gets hot and needs to expand, it cannot go back to the reservoir. Instead it will push the brake caliper pistons out causing the front brake to lock up. You are very lucky you did not get hurt or get into an accident.
The same thing can happen on the clutch side. When that happens, the expanded fluid would gradually push the clutch slave piston out, causing clutch slippage and in most cases will cause the friction plates to burn some of their friction material and the heat created by clutch slippage can cause the steel plates to get warped. That means you will need a new set of clutch plates and possibly a new clutch pressure plate if that happens.
There are no visual marks on the brake and clutch master cylinders to let you know where the bleed hole is and how far that screw can be turned in. At the factory they set up the plunger at its proper location and then put a seal on that screw to prevent people from fooling around with it. More than likely you broke that seal/wax when you decided to adjust the lever position.
Locking your front wheel was the hard way of finding out that the plunger was resting in front of the bleed hole. A simple way of find out if the bleed hole is blocked is to connect a bottle with a tube attached to it to the bleed hole on one of your calipers. Put brake fluid in the bottle. Remove some of the fluid from the brake master cylinder reservoir so that the fluid level in the reservoir is slightly above the MIN line. Put the cap back on the reservoir but do not tighten it all the way. Now loosen the bleeder valve on the front caliper and try to squeeze in some of the new brake fluid from the bottle with the tube attached into the caliper and the lines attached to the banjo bolt through the bleeder valve. If everything is working OK, you should be able to see the brake fluid rising in the reservoir. If the adjustment screw is screwed in too far blocking the bleed hole in the master cylinder, after the caliper pistons are pushed out, you will not be able to add any more fluid to the system through the bleed valve on the caliper and the fluid will not rise in the reservoir. You should try to do this slowly to make sure that the fluid is not spilling out of the reservoir getting on fairing pieces.
If the fluid level is not rising in the reservoir, slowly turn that adjustment screw on the master cylinder CCW while trying to add fluid through the bleed valve, until you unblock the bleed hole in the master cylinder. After the bleed hole is unblocked and the fluid starts to rise in the reservoir, turn an additional one to two turns to make sure the bleed hole is FULLY unblocked.
Another method would be to take one of the calipers off the front wheel. Try pushing the caliper pistons back into the caliper cylinder when the lever is out (rest position) and watch the fluid level in the reservoir. If the fluid level rises, that means the bleed hole is not blocked, if the fluid does not rise (pistons do not go back in that far) that means the bleed hole is blocked.
It might be difficult to push the caliper pistons back into the caliper. First of all there are four of them and if you push one in, one of the other ones might move out. Use a wide blade putty knife and place it between the pads and try to push the pads in. If you have a bicycle tube sitting around put the bicycle tube between the pads and pump some air in the tube. You might need to fold the tube between the pads few times but that should work.
On the clutch side, remove the clutch slave from the case and push in the slave piston back into the slave cylinder. If the fluid does not rise, the bleed hole is blocked. Back out the screw on the master cylinder until the fluid rises. Go another 1 to 2 turns out after the fluid starts rising.
-Fariborz
