yz 85 bogging down

recently had a friend purchase a 2007 yz85 from california less than 1000' above sea level. We live at 4100' MSL. The bike from the get go was very boggy at run up... totally ok when at high rpm (unlike our 2005 yz85). Plug is fouled (black, wet, like super rich). Not sure what to do about it any help would be appreciated.

Carb might need cleaned out,or it might be a jetting issue.

I gree with kx100. Maybe try cleaning out the carb. Then if that doesnt solve anything i would take a look at you jetting, you could be running to rich.

BTW what fuel-oil ratio are you running?

32:1 on mix.... replaced the spark plug as a temp fix.....more responsive through out for now.....

Thats good man but maybe try mixing 40:1, but if thats working for you then i wouldnt change anything, but usually that helps out

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