2005 CBR600RR - Only has about 11,000 miles on it. Always ran great until now. The idle is erratic. When you start riding it's still erratic (trying to cut out) and lacking power until about 2,000 RPM. Then it wakes up and runs normal. Based on the fact that it runs good at 2,000 RPM and higher, I assume the fuel and spark are good, there's no bad fuel, the intake is not blocked, etc. Isn't this more along the lines of sensors or computer controls? Do vacuum leaks only affect lower RPM, or do they also affect higher RPM? Ideas?

 

Maybe could do with a IAC sync

 

It's definitely possible. The manual has you check that after checking five other things. First is plugs. With only 11,000 miles I had high expectations. When I pulled them out, sure as heck they were a good color and the gaps were right on the money. I figured since they're not easy to access, while I'm there I will change them out anyway. But the bike shops was already closed on Saturday evening and will not open again until Tuesday. So I can't refire it to check the IAC unless I go to the trouble of reusing the old plugs. Not worth it for the sake of a day or two. I noticed there's a separate IAC valve for each jug, #3 being the fixed one that you synch the others to. But I also see an IAC thermal valve mechanically attached to the linkage for all four. It has coolant lines in and out, so I assume it changes with temperature. I don't suspect this part, however, on account of the symptoms don't seem to change at all with the engine cold or hot. What worries me the most in the mean time is the possibility of the ECU being the problem. The manual doesn't mention it in the "Poor performance at idle or low speed" section. But isn't there a chance that's where the fault lies? Also, is it possible it could be caused by the MAP sensor? I haven't found anything yet that might be a vacuum leak. I'll have to keep checking. In the mean time, to recap - with the engine cold or warm, the symptoms seem the same. Erratic idle (not too high or too low, just won't stabilize) and erratic RPM combined with hesitation and low power until 2,000 RPM. It also stalls sometimes when you stop. Any other ideas?

 

Dont think the ECU is a problem, dont think its the wax unit , that would give you high revs at start up and settle down once warm, but it could be the flow to the wax unit ,sometimes the pipes get gummed up , worth cleaning out the pipes leading to the wax unit while your stripped down , but would mean changing coolant

 

I had it tore down enough to get to the spark plugs by the time I had checked everything else and hadn't found any problems. I figured even though the plugs had only 11,000 miles on them and had good color and the gaps were perfect, I might as well replace them while I had access. Amazingly, with the new plugs the bike runs like new! It's the goofiest thing I've seen in a long time, but I'm not complaining. It just was surprising on account of Honda says inspect them at 16,000 miles and replace them at 32,000. NGK says that particular part number is good for 80,000! Well, at least the bike is back in business for the good weather. Perhaps this discovery can save someone else the trouble of chasing the wrong things for the same symptom...

 

Interesting discovery! I have 30,000 on my 06 and as far as I know, plugs are original. Sometimes, stuff that shouldn't just goes bad...