3 Cylinders!!!

G'day people!
So i just recently gave the bike its first proper clean, and tidy up since i have had it, basically pulled all the nuts and bolts of the body apart cleaned her up, made everything look nice and tidy!
Anyway for some strange reason now its running on 3 cylinders.. Now i did wash the bike but i have doubts thats the issue.
Story goes:
Rode bike after clean up for about 30 minutes, everything seemed to be running ok..... then pulled up at a set of lights and for some strange reason bike is idling fine, give it a bit of a rev to take off and it make a loud snap backfire noise... so i assume maybe fuel ???
Anyway about 2-3 minutes laters it starts to run on 3 cylinders and sounds like a bad arse WRX engine thrown in there!!!
Any ideas wat it might be ?
So i just recently gave the bike its first proper clean, and tidy up since i have had it, basically pulled all the nuts and bolts of the body apart cleaned her up, made everything look nice and tidy!
Anyway for some strange reason now its running on 3 cylinders.. Now i did wash the bike but i have doubts thats the issue.
Story goes:
Rode bike after clean up for about 30 minutes, everything seemed to be running ok..... then pulled up at a set of lights and for some strange reason bike is idling fine, give it a bit of a rev to take off and it make a loud snap backfire noise... so i assume maybe fuel ???
Anyway about 2-3 minutes laters it starts to run on 3 cylinders and sounds like a bad arse WRX engine thrown in there!!!
Any ideas wat it might be ?