I have an 03 CBR600F4i that has developed a problem that seems to be eluding dealers and myself. When you rev it or ride it hard it feels much rougher than it should and kind of struggles to go. I know it is not right as when I first bought it there was no evidence of this problem. So far the bike has had a new CCT, new set of plugs, Air filter and Oil filter. It has had a full fluid change as part of an intermediate service (12000 miles). I have sytematically checked all the sensors such as the MAP and IAT plus all coil packs and injectors. Some STP fuel injector cleaner has also been run through. All plugs produce a good healthy blue spark and there are no issues being raised on the FI diagnostics.

After inspecting the vacuum hoses which are also all good and each spark/coil pack I checked the throttle body was ok, all chambers are sucking air in quite evenly but when revving the sound from each is very throaty sort of a rough growl rather than a more even buzz and of course there is still what I would term as being a bit more vibration than I would expect. In fact to give you an idea you can feel the garage floor vibrating at around 3500rpm, that's surely not right is it?

I have run out of ideas and things that both Honda and Haynes suggest - the only things I can think of now are valves, timing, compression or exhaust system. Is it possible for a problem in the exhaust system to cause the bike to run rough? The bike still has the standard can and pipes, I cannot see any leaks in the system and have tried to cause it to force out of any gaps or holes by obstructing the exhaust outlet slighty. Exhaust fumes smell normal, no evidence of fuel or oil.

Sorry it's a real tough one but I would like to try and find an answer before I just accept it and live with it like the Honda dealer suggested so any advice would be appreciated. Thanks

 

Have you always owned the bike? (original owner) If not was it ridden hard or stunted? Any smoke? If so what color? I have seen exhausts cause issues, it is fairly easy to undo the midpipe on the exhaust and remove the muffler, I would undo it and start it up and rev it (fun to do anyways) and see if there is a noticeable difference. I had a friend that had a mouse make a nest in his pipe over the winter and it ran like crap till he figured it out........it is possible your stock exhaust could be very clogged if the gas in your area is really crummy or something.

 

Grab a glove, and check if all four of your exhaust pipes near the head are getting hot. If one's cooler than the others, it's probably not firing well. And, yes, I would check your timing, as well.

 

Thanks for the advice so far, yes I have tried the glove & checking if each exhaust pipe gets warm - they all do and I already know that there is a good blue colored spark from each coil pack and plug so I think I can rule out ignition problems on this basis apart from timing.

No I am the second owner but there is no evidence to suggest it has been mistreated and there is a good service history with the bike too. No smoke apart from when warming up but understand this is normal (white color so assume damp in can). Think I will take it off and check as suggested though. The only other thing I thought it could be is a failed gasket on one of the pipes.

 

I would take a can of fuel injection cleaner. Fill the gas tank up with gas, dump the FI cleaner in it and go for a good long ride. Try to run ALL of the gas out of the bike. I think its just dirty injectors, causing a sputtering under load. I would try this FIRST. If that doesnt fix it, then i would look into it deeper. Alot of times, situations like this is just a simple little FI fix with some FI cleaner....Also try driving the bike HARD with the FI cleaner in it. Just incase dirt is in the injector, that should force fuel through it a little harder.....=-)

You would be surprised what a little FI cleaner will do....=-)

PS: Timing usually causes the bike to act up no matter what RPM range its in.

 

it could be a 100 things....but here try these...sync the throttle bodies. check to make sure that the choke(fast idle)isn't hanging up.i would also take the pipe off and make sure that nothing got in the chambers.also a bad regulator used to make the 900rr run like **** so check that plug to see if the contact is good and not meltedor corroded