Hello all. Im new here and to the bike scene. I recently picked my first bike up, 1997 CBR 900. I need some help getting the bike running. When the bike cranks it will sometimes back fire and shoot flames out the exhaust. The bike did start once for about 2 seconds then died. The previous owner said he replaced the stator, rectifier and the pulse generator and he said that the bike would start up every now and then. I pulled the plugs and they look fairly new however they were black and had gas all over them. If any one can help me i would much appreciate it. Thanks

 

If the plugs were black & had fuel on them then they are fouled & should be replaced. Have you heard the bike run before you bought it? Has it been sitting for a long period of time? Is the battery fully charged?

 

it could be CDI is the problem.

 

I picked up a new set of plugs and will install when I get home tonight. It had spark but it wasn't very strong when it was turning over.

 

I put new plugs in and turned it over and it back fired. Threw some staring fluid in there and she backfired then started up. My father kept spraying it in the carbs to keep it running and we noticed it backfired numberous of times and the bike wouldnt stay running unless i kept giving it throttle. I hooked the gas tank up and tryed starting it and nothing. Any ideas?

 

Ok guys/gals, heres where im at. I pulled the carbs of last night and took them to work and cleaned them. I noticed the valves look very weird to me. Im not familiar with how they open and close and i noticed 3 cylinders were closed or close to close, and 1 cylinder was noticably open. I decided to check timing because the bike is backfiring on startup. I pulled off the cover by the cam chain, Put cylinder 1 at TDC and the T lined up with it. I then proceded to lift the valve cover so i can see if the IN and EX were lined up with the head. Every thing was lining just fine so im not really sure where else to go about this. I would like to get the bike running ASAP so if any one can help it would be much appreciated. I have a few pics also if needed. Thanks

 

if you knew somebody that had CDI , u could borrow and test it..

faulty CDI Symptom: backfired, rpm will dropped when u are revving..

 

when me and my father actually got the bike started i could rev it up wit no problem other than a few backfires.
I was told by the previous owner that he though it could be the CDI box. I dont know any one with a bike like mine for me to test the CDI box and i cant see me dropping $100 into a CDI box for it not to fix my problem. Its a gamble so im trying to rule out all other possibilities before purchasing.
I was thinking timing because it was backfire while cranking with brand new plugs in it.