Powder coat / front brk and clutch lever

I was bored the other day so I decided to powder coat the front brake and clutch lever's on my 09' & 11' YZ450F's. Well, the powder coating went really well, looks like i had bought them, but the front brake seemed really sensitive afterwards. Like very little effort needed to apply the brakes, Almost too tight.

Do you guy's think that the small amount of powder coat that is inside of the plunger socket on the lever has anything to do with it? I bled the brakes and the 2011 and seems to be more like stock but the 09 is still very hard.

took the front brake lever off the 09, cleaned out the powder coat in the socket portion where the master cylinder plunger engages, reinstalled the lever and the brake is still too tight.

all i did was remove the lever, paint it then reinstalled. no adjustsments were made. so why is the brake so sensitive?


Brake levers tend to have a small amount of "pre load" on the plunger. Basically it keeps the plunger far enough inside the master cylinder bore to lessen the possibility of contamination(air, water etc.. among other reasons). When you removed the lever this could have allowed the plunger to move up in the bore to a place it doesnt normally occupy. When you reinstalled the lever the fluid displaced by the increase in volume below the plunger would have been pushed into the caliper effectively moving the piston in the caliper closer to the pad. You should be able to bleed the brake and solve the problem. Keep in mind when bleeding there is minimum distance the lever should be from the grip while bleeding. Also I've noted in situations like yours the the air they may have been drawn in tends to be really fine bubbles that are difficult to bleed out. Patience will go a long way in the process.

Edited by to hare or not

Thank you for the detailed explanation. I will trouble shoot accordingly from what you have stated. I'm going to remove the master cylinder cover(remove a small amount of fluid), then place a small clamp on the brake caliper and push the pistons in, hoping this action will force any air up and out through the fluid resevoir. Bleeding the brake the conventional way didn't help.

Thank you again!

It was detailed, but not completely correct. In normal operation, the master cylinder piston always returns to a position that opens the fill port at the bottom of the reservoir when the brake is released. This allows the fluid to fill the caliper and line as the brakes wear, and to back up into the reservoir as it expands with heat.

What may have happened, although nothing you have said accounts for it, is that the piston may now be closer to closing off the port, which is where real braking begins, than it previously was. Remove the master cylinder cap and push the caliper piston back. It should be reasonably easy to move, and should push fluid back into the reservoir (watch your eyes). If it won't do both, don't ride it until you find out what's pushing the piston in too far at rest. The brake may apply itself as a result of heat expansion in the fluid if it can't move back up.

Bleeding the brake won't help. Air in the line would have the opposite effect.

All due respect grayracer I agree with everything you said with respect to the fill port and return position. However the condition I described can and does occur. If the plunger seal is moved to an imperfect area on the bore air can be drawn into the system I've seen it many times on various systems(admittedly I've only had it occur with hydraulic clutches on bikes). What I've noted on master cylinder disassembly is typically the piston in some cases is not allowed to seat by various factors of control lever wear and or previous incorrect installation dirt contamination etc..when this happens corrosion can occur with dust seal failure and cause air to be drawn into the system once the plunger is allowed to return to its "normal position". Once the air and or moisture is in the system its displacement can cause the problem I described in my earlier post which is brake sensitivety. The OP didn't elaborate on level of sensitivety or the effect of continual application. Of course we all know that once your past the initial additional volume effects of the contaminate and lever pressure is increased the air and or moisture will compress and cause the brakes to become soft. The times I've experienced this effect is when air has in someway gotten trapped beyond the fill port in the very small area that is normally created when the piston is fully retracted. The only way I've been able to remove this air has been by small continual applications of the lever followed by a full bleed. Looking down in the reservoir (with safet lasses on and mouth closed as I can attest) You will see tiny fine bubbles coming from the the fill port orifice. If you do the small lever pumps too fast a tiny squirt of fluid will get you as the piston moves past the port. The reason I mentioned bleeding first was because it was the quickest way to rule out the problem I mentioned as well as yours since it will not bleed properly if the piston is being held too far in and of course you have the added advantage of new fluid which most peopl need to cycle out anyway.

What may have happened, although nothing you have said accounts for it, is that the piston may now be closer to closing off the port, which is where real braking begins"

" Do you guy's think that the small amount of powder coat that is inside of the plunger socket on the lever has anything to do with it? "

This is why I had asked the question above

I really appreciate the help guy's. Thanks

My apologies. When I don't sleep fir a couple days nothing in my noggin works right. Ignore half of what I said trust everything grayracer said. And to answer your question in short no a small amount of powdercoat should not make a difference.

It shouldn't, but it depends on how thick it is, and the thickness of the coating can vary on small, irregularly shaped objects like a brake lever. You might try cleaning out the dimple with a drill bit just until you hit bare metal, or see if there's an adjustment on the end of the M/C plunger where it contacts the lever.

One other thing that could have happened also is that you may have had a small bubble living at the top of your brake line for a while that you weren't aware of. Then, when you worked on the lever, the bubble, if there, could have been dislodged into the reservoir, and your previously "normal" brake feel became tighter as a result of being bled. Either way, air in the line will not ever make the brake tighter or stiffer or more responsive; quite the opposite.

As long as the system passes the flow back test I mentioned above, you don't have to worry about the lever pushing in too far. From that point, you should be able to "adjust" the lever to the feel you want.

today i back flushed the front brakes on both my bikes. the feel is "much" better now. we have thursday night practice at a local track so i'll test them out then.

thanks again for the help guy's!

Edited by stroker101

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