my new bar on my stihl 034 looks burnt on the bottom why?

All of the previously mentioned items but sometimes the bar oil can leave a nicotine style colouring to your bar but multigrade car oil doesnt - I am not saying use engine oil in your saw but noting that bar oil can do this. typically a blunt chain is th usual culprit - make sure it chips the wood when cutting and isnt making sawdust.
Seasoned hard wood can make more heat than unseasoned.

Steve
March 2009

Lack of oil

Incorrect oil in reservoir

Chain overtightened

Chain dull or blunt

Twisting the bar whilst cutting

Incorrect chain fitted

.....or a combination of several of the above

pleasant
March 2009