Wrong brake lever or broken master cylinder?

I'm on an 08 yz450f. Had a bad wreck in practice and broke both levers. I went to a vendor there and all he had was an 07 yz250f set of levers. He said they were the same. They looked similar so I took them. They fit but after I rode around for a bit, my front brake locked up. Once I took the brake lever off, the brake unlocked. Is it the lever or did I jack up the master cylinder? The pin that the lever contacts with hangs freely but seems to compress the brake properly. I never paid attention to how the pin functions before so I'm not sure if that's normal. I ended up running the race with no front brake.

Any help would be nice.

The '07 YZ250F lever should have worked, but it may not have been the correct one for that bike either. The brake locked because the lever fit incorrectly, pushing the piston in farther than the fill port in the master cylinder. Then, when the fluid heats up, it can't escape to the reservoir, and applies the brake instead.

The lever is wrong, simple as that. Compare with the original one at the point where it contacts the piston. You'll see what I mean.


Get yourself some bendy levers!

I've seen several times an aftermarket lever do what is happening here. The levers are real close and fit but need to be filed down to allow piston to retract all the way as Gray has stated. This sometimes happens even if the lever is supposed to be an exact fit for the particular bike. This is one of those things that really gripes me about aftermarket stuff. A lot of it does not fit and work as good as OEM....

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