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Hello fellow Kawasaki riders. I am new to this forum and decided to join because I recently successfully rebuilt a Kawasaki Bayou KLF400 4x4 from front to back. This included a complete rebuilt of the top and bottom ends of the motor (including crank, crank case, bearings, seals, rings, valves, etc., rebuilds of the front and rear differentials, carburetor, radiator, front and rear brakes, electrical components, etc, and have learned a lot along the way. I plan to share some of this info with pictures in different post if it will help other KLF400 owners. My first and most important suggestion is to purchase a Clymer manual for the Kawasaki Bayou KLF400. I paid $25 or so for mine new and it is worth it's weight in gold. In my opinion, it is not possible to do a correct and proper rebuild without this manual.
 

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Kawasaki Bayou KLF400 4x4 Front Brake Master Cylinder

Due to age and wear, I had to replace both the front brake calipers and rotors on my Kawasaki Bayou 400. My Clymer manual states the minimum wear thickness of the rotors, so once they are below that thickness they must be replaced, which is why I replaced mine. The calipers were locked up and would not move. It is easier and usually cheaper to just buy new calipers than it is to rebuild the old. I also took apart the master cylinder to clean old fluid and crap out of it. After working through this, I would recommend buying a master cylinder rebuild kit for $17 or so online. Old brake fluid crud, dirt, etc. can build up around the seals and prevent the proper pressure build-up in the system. I include pictures of the old and new parts for reference. They are easy to install with a little patience and some common sense.

After installing the new components and filling the master cylinder and lines with new fluid, I began to try and bleed the air from the brake system via the bleed valves/nipples on the calipers. However, I could never get the system to pump up even though there was no air bubbles coming from the bleed valves on the calipers. As a side note, I put a small piece of fuel line on the end of the bleed valve/nipple and allow it so fill a little with brake fluid. This makes it much easier to bleed the lines (see pictures) and prevents the calipers from sucking in air. Upon re-inspection of the lines, calipers, and master cylinder seals, I found no leaks of fluid or air. However, in the bottom of the master cylinder reservoir, there is 2 holes. One is through hole (it goes all the way through the bottom of the reservoir into the master cylinder) about a 1/16" in diameter and the other is a half drilled hole also about 1/16" in diameter. In the center of the half drilled hole, there is a very, very tiny through hole that also goes through the bottom of the reservoir into the master cylinder. My Clymer manual refers to it as a relief port or hole and does not say much at all about it. This second hole is very tiny and is hard to see with the naked eye and is also very easily filled with old brake fluid crap. On my Bayou, this hole was clogged and I had to take alot of compressed air and some carb cleaner to clean it out. Be very careful using anything else on this hole because you could ruin it, as the master cylinder is only aluminum. Anyway, what I realized was, the air that gets trapped in the brake line up by the master cylinder cannot escape without this second tiny, tiny hole cleaned out. If this little hole is clogged, the air will not be forced down into the calipers, but will hang around by the master cylinder and prevent you from pumping up the breaks. Be very careful, soak the hole in some carb cleaner, and then blast the hell out of it with compressed air. I included some pictures for reference.
 

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