i have the same problem
hi there i have the same problem did you find out what was wrong with the bike ..
i just got my gz125 back 6 weeks ago from garage that fixe a leaking carb and now i have loss of power and cutsout after a few miles
looks like my bike is running rich black velvet over spark plug fitted new plug still black velvet coverd
well the money i have trown buying this bike and garage repairs so far looks like i will sell it and do my das
done my cbt july 2011 my gz125 written off by van driver reversing into me at red lights in oct 2011
got a nice shiney unreliable gz125 as a replacement for my written off bike ''ho hum'' car driver 12 years getting bad vibes from motorbikes
any help would be much appeciated