motor trouble... im stumped

[Pont400ex]

Rode the 400 this morn, rode fine all day until i hit a stretch of more than a mile or so. Had it 5th gear pinned, then at the end of the straight away the engine cut out and bogged down almost like it was out of gas but it wasnt, kinda felt like the back wheels locked a bit, and it sputtered but didnt stall, but when i got back on the throttle it would hardley move. Some black smoke out the exhaust. Let the bike cool, tried to start it back up, wont turn over but sounds like it wants too. Where should i start too look.
Mods are bored to 408, high compression pistion, stage one hot cam, big gun rev box, full yoshi. thanks

[iownatoyota]

check your coil to see if the connection is bad from the coil to the spark plug, i have a bad wire on mine and it cuts out sumtimes causing a similar reaction, its quick and easy so its a decent place to start, but it sounds like u should do a compression test too.

[pitkendall]

take the timing cover plug out and put a 17mm socket on it with a ratchet or strong arm and try and turn the motor over by hand i hate to say it but sounds like it may have gotten oil starved or was just ran real hot from runnin wide open for such a long time and seized something up

[Gibson]

^^i agree. it probably over-heated and burnt something up.

[ngates788]

almost sounds like you might have fried your piston

[timmy400exfast]

pull your filters first see if there clogged if they are you prolly took out the piston same thing happened to me exept theres a filter a the bottom of the oil tank check that one to cause thats the one that got me