kazuma cheetah 125 speed problems misfireing :(

[adamaj]

hi guys ive recently bought a kazuma cheetah 125cc 4 stroke when i bought it it had no mot but everything seemed ok it was a kickstart as the guy we bought it from said that he tried to use electric start but just caused him problems so we kicked it over first time no problem.so we rode it home and got 65 mph no problem.

now ive just had it mot'd they replaced the wheel bearing a rewired a new light as old one wasnt road legal and they put the electric start battery pack on my bike as it was now getting colder and would need to up and go without any problems to work. so i payed my money and went on my way.

i tried the electric start as we left but nothing happened but was eager to ride so kicked it over and after 5 or 6 failed attempts my uncle kicked it over and we went on our way immediatly pulling a way seemed sluggish and slow the bike started misfiring backfireing and i tried to give the bike full throttle but the bike just spluttered like it wanted to give more but couldnt i managed to get 39 mph on the way home and wasnt pleased

does anyone have any ideas what this could be what i would need to do a list of things would be great as i can tinker over the weekend please let me know as soon as possible thanks guys