master cylinder swap problems

did the bar swap on my 550 this week, and the first master cylinder i got was for a regular 550, but the sight window leaks, so i got a different mc off ebay for a 05 ninja 250 (pretty sure it would work). Went to hook it up today and i get no pressure at the lever after i bleed the air out of the m/c before moving onto the caliper bleed screw. No matter how much pumping, smacking, jiggling, etc seems to make any kind of pressure at the handle. Swapped the other m/c i wanted to replace back on and was able to pump the handle a few times and bleed the air out and get pressure at the handle, so i know there was no huge air pocket in the lines.

Did i screw up and the 05 ninja mc isnt compatible? or does it seem like i would need to rebuild it? Ive never had one go bad, so i wasnt sure if rebuilding it was what is needed, or if there was something different about the ninja 250 m/c.

All thoughts, opinion's, flaming are welcome.

well i was pissed off about it not working, went back out to the garage to mess with it a bit more, turns out it does make pressure, you just have to have the handle pulled basically all the way in to lock the front brake up, and by lock it up i mean me pushing against it with my weight. So i guess that would mean that the piston diameter is too large....or too small?

figured id follow up so if anyone else was searching for this, the piston diameter of the 05 ninja ex250 is smaller than the piston diameter of the kz550 piston. lol anyone want a m/c for a ninja 250?

If you use a pump/vacuum bleed system to inject the brake fluid, the ninja 250 MC will work just fine.

It will still require a litle more handle, but not much. When that gets ral bad, you should blame your lines, not the MC.

Best of luck.

huh thanks for the response. It was just annoying to be able to switch back to the other m/c and have it work fine, handle only pulls about halfway and its locked, where the ninja needed alot more pull, basically to the handlebar and locks. I don't have a vac, but might try and swing by the parts store before they close tonight. Mitey vac should be ok?

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danhalen wrote:

huh thanks for the response. It was just annoying to be able to switch back to the other m/c and have it work fine, handle only pulls about halfway and its locked, where the ninja needed alot more pull, basically to the handlebar and locks. I don't have a vac, but might try and swing by the parts store before they close tonight. Mitey vac should be ok?

Yeah, should be fine

Thanks for the reply's !

thanks for the input guys, finally figured out what was up with the m/c problems. Stock mc is 14mm, 1st replacement i bought was a 5/8" even though the guy had it listed for a kz550, and ninja is 1/2". Didnt have time to buy the vacuum bleeder that night so i did the old clamp the lever back with a bungee cord trick. Thanks again for the input.