How about something sarcastically silly like
"If you can read this, you just lost!" or
"Sucks getting beaten by a 600, doesn't it?"
I know that last one from personal experience......
Got spanked up in the canyons by a REALLY good rider on an R6. He had the damn thing leaned over so far, I thought for sure he was about to lowside....so then he downshifted and beat me to the marker by oh, let's say about 1/4mile..........pesky little 600's! 
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Cosmo
'97 Katana 750
"If you can read this, you just lost!" or
"Sucks getting beaten by a 600, doesn't it?"
I know that last one from personal experience......
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Cosmo
'97 Katana 750