I have been rebuilding a cbr600f and I was able to get it running, ran strong but the next day it wouldn't start at all,

It will on occasion hit giving a backfire

I have rebuilt the carburetors, new pulse generator, new battery, I have also checked the coils and wires they are still at the correct resistance as stated by the manual.
it almost sounds like a timing problem so I replaced the CDI with one from eBay, but i still can't get this to run ... looking for any suggestions,

Im thinking that it is an electrical issue but since it ran for awhile (about an hour) I'm at a loss

Thank you for any help you can give

Mark

 

Spark, fuel, compression to make it run. Which are you missing?

 

its all there spark, fuel, air and compression

It seems like a timing problem and if its not electrical then maybe its mechanical like the timing chain slipped a tooth but then would explain why it ran before, Im thinking a sensor, relay, or diode

Mark

 

It will still run if its a tooth off, just not well. Compression will be down. What are the compression #s for all 4 cylinders?

 

I would take another look at the carbs.

 

I agree with Hamlin. The carbs need to be impeccably clean, particularly the pilot circuit. The pilot jets need to be taken out and individually cleaned. You need to be able to see light thru them. I probe with a strand of copper wire. Pilot screws need to be taken out and carb cleaner and compressed air sprayed both ways thru the pilot circuit. Pilot screws should be set at 2 1/4 to 2 1/2 turns out and then adjusted per manual when hot.

These bikes will will be hard to start if the pilot circuit isn’t clean and set right.

To test the theory spray a little starting fluid in the carbs. If it fires and revs...carbs are not clean.

 

I would like to thank everyone for their input , I checked the compression got a new cdi card, new coils and i even checked to make sure that the cams were at top dead center, after all that still got the backfire... in the mist of planning hari-kari it dawned on me that the only this i didn't replace were the spark plugs!!! Since the bike was running i didn't think of the plugs as being the problem but guess what they were the problem!!

I have since replaced the plugs and she seems to be running fine... i know i will have to tweak it a little but it runs!! and I just wanted to say thank you for all of your encouragement and your knowledge!!

Thank you

Mark