Well we just replaced the headgasket and valvecover gasket, and forgot to replace the tensioner. We had our bike mechanic look at it and he said to put a new tensioner in and it would run fine...when starting it, it will idle but the chain is so loose it will just jump time and you can hear the chain skip...
I have all the parts necessary to fix it, and its deffinitely a reasonable price...heres some pics.