Hi everyone hopefully someone may be able to help I’ve got a 1993 Honda cbr600 f2 that’s had some running issues recently so just wanted to know if anyone knows what may be at fault, bike was running fine then one day on the way back from a ride it began to run on only 3 cylinders so since then I have given it a service while it was laid up including new plugs then replaced the ignition coils now By this time it has also developed for 3 cylinders to not running at all here’s the odd bit I replaced the coils and thought all was well because I then started it and let it run up to temp and it ran fine exactly as it had done before so I thought great and then waited till there was decent weather the next week and bam the issue has returned exactly as it was, the only thing I did think is it could be one of the vacuum lines caught as I roll it down a ramp to get it out and maybe one was caught when I did that but I’m not sure where all of them run, probably worth saying too I took the carbs off and cleaned them while it was laid up.

any ideas let me know?

 

Not having the vacuum lines connected will cause bad running. If you're not sure where everything goes and are not able to follow the workshop manual, you probably need to take the bike to a mechanic?

 

no all vacuum lines are connected and besides it doesn’t run at all, tried a mechanic too but every one near me is booked for months at the moment. I just can’t understand why it ran so perfect again and then decided to stall out and not run again for no apparent reason?

 

First, how did you determine it was running on only 3-cylinders? Did you measure temperature of each header tube and found 3 of them at 575F and one at 75F?

Or is bike just stumbling and not running smoothly?

Can be numerous causes of that... The stumbling was probably just transition from running fine to not running at all.

1. post photos of old spark-plugs that you pulled, numbered in order.

2. measure impedance of primary & secondary windings of both old and new coils. Post all 4 numbers here. ohms 1-4 = ???

3. do compression test twice. Second time after squirting 1-2cc of oil down spark-plug holes. PSI 1-8 = ??

4. measure petcock flow-rate. How many CC petrol did you collect in 10-sec?



5. what vacuum-level was required open petcock fully for maximum flow?

6. did vacuum-level stay steady? Or did it drop and you had to keep pumping to keep vacuum at same amount?

7. insert vacuum-T into petcock vacuum line to re-connect carbs AND measure vacuum at same time. Crank engine for 5-10s. What vacuum-levels do you measure when engine is cranking? InHg=??


These are steps that pro-mechanic would do anyway. Straight out of manual. You might as well do them yourself and fix this.