Hi I have a cbr600 I have recently bought and it was parked up for around 2 years, it starts but not running right, the carbs have been cleaned and didn’t make any difference what could I check next? Thanks

 

Have you checked all the cylinders are firing? Check if all headers get hot.squirt water on them so you don't get burned. check all plugs are sparking. is the fuel fresh ?

D.D.

 

When was last time valve-clearances checked and adjusted?

If it idles OK, but dies when open throttle, carbs are not factory-fresh clean. Many expert mechanics have had to pull carbs 4-5x for ever deeper cleaning before they were restored back to factory-fresh clean OEM condition. You actually need carb restoration, cleaning is not enough.

1. completely disassemble carbs to every last nut, bolt and individual component. If it can be further taken apart, do it. Take lots of photos and videos so you can put it back together properly. Compare to factory service-manual, just in case previous owners modified anything. Needle jets upside down is common mistake.




2. Completely disassemble emulsion-tube and pilot jet.


3. clean out all secret hidden passages in carb-body with PEA-based fuel-system cleaner and . Note: spray “carb-cleaners” no longer work due to removal of chlorinated compounds. Thanks a lot crunchy-granola, tree-hugging, bark-eating smelly hippies! For different model, but yours will be similar:



4. Poke out all lateral bleed holes with soft copper wire. Dried petrol turns to plastic and cannot be dissolved again. Must be mechanically scrubbed away. Also poke out all bleed-holes in carb-venturi towards float-bowl.


5. Ultrasonic soak everything for days. Micro soda-blast everything before reassembly.


6. Replace all rubbers: float-valves, pilot-screw O-rings, fuel-rail O-rings, float-bowl seals, slide-diaphragms if needed.


7. Set float-levels to stock. Verify with external wet-test when back on bike.


8. Do rough bench-sync. Then fine-tune with manometers


If you skipped any if these steps, that’s why bike isn’t running right. When carbs are restored back to factory-fresh clean, it’ll run like brand-new off showroom floor. That kind of restoration requires lots of specialised equipment and decades of experience on hundreds of sets of carbs and even destroying some in process of learning. Best to send to pros for expert restoration, reasonable fees and quick turnaround.

https://customcarbservices.com

 

thanks for the reply, 2 headers are piping hot but other 2 are only warm, there is spark and fresh fuel. I’ve left it for a few weeks as been working and now it running a bit worse again, thanks

 

It certainly looks like you will need to have another go at the carbs

 

If the two hot are 1&4 and the two warm are 2&3 or t’other way about then suspect a coil - check for a spark on the colder cylinders.

 

This could be as simple as cheap nasty chinese fake plugs. If it's 1 and two cold (as above post), swap two working plugs with non running cylinders plugs, see what happens. If the problem moves with the plugs, buy 4 new genuine plugs.

D.D.

 

True, lots of countrefeit NGK and Denso plugs out there. Even major retailers like Advanced Auto has been hoodwinkled…

Easy test is just swap 1 & 4 with 2 & 3 plugs and see if heat levels swap.

Can also measure coils and plug wires. Plug caps often gets worn out where they clip onto wire. Usual fix is to disassemble, trim off 1/4” from plug-wire and re-install cap.

 

Thanks for the advice everyone , will do some checks you have mentioned and hopefully get to the bottom of my problem, thanks again appreciate the advice .