Hi guys,

I purchased a cbr600 f4i 2003 around 1.5 months ago. Right from the get go I found what feels like a dead spot in the rpm.

The bike pulls nicely right up to 6k and then from 7-8k it's really hesitating/bogging then from 9k or 10k onwards it just picks up and fly's like **** off a shovel.

-Bike idles perfectly at 1.5k.
-has no issues revving up in neutral
-Temp sits around 79c when riding. (Never goes above 108c in standstill traffic jams)
-cant see any oil leaks etc.

Bike came with a black widow end can, after reading many comments online it was suggested pc or stock exhaust. Well I've fitted a stock exhaust and it's still doing it.

Local garage took it out for a spin and he said he couldn't feel anything wrong with it. I told them he needed to get up to 7k however given that it was a built up 30mph town setting I don't think he got anywhere near where you would start feeling it.

I know this isn't right, it just feels spluttery and bogging until you get through that rpm range

 

update to this:

I have purchased an OEM exhaust as a few people on another site said it could be from an aftermarket end can. the issue is still present with a stock exhuast.

again no leaks, not overheating bike revs fine. just as soon as you get to 7000rpm there is nothing there.

 

The only thing I can think of would be to check/change the spark plugs. Hopefully someone with a little more expertise than me will chime in!

 

I'm just going to ask a few questions because, well - I don't really have an answer but I know someone here does we just haven't gotten there yet. I'm actually shocked too. @dannoxyz usually chimes in on these kinds of threads and he's pretty good at them too.

Does it have a Power Commander on it? I'm guessing no since you didn't mention it and you did a good job explaining things in your original post.
Does it happen at 1/4, 1/2, 3/4, full throttle or any throttle position?
Is it just a little hesitation or does it fall on its face?

 

Do you know its history? Has anyone been messing with it that you know of?
Have you checked the air filter, could be dirty / blocked causing it to not fuel properly. Mine had a flat spot a little lower c. 4.5-5.5k (but not spluttering) which was sorted by a PC and mapped on a dyno.
If in doubt get it on a rolling road and the tech will quickly figure out whats wrong as it does not appear to be anything obvious. Prob cost $200 but worth it as you are just guessing with replacing parts.

 

Could be fuel-system problem or ignition.

Try fresh tank of petrol to flush out any possible contaminants, water very likely if it's been sitting for more than couple months.

Run through some PEA-based fuel-system cleaners.

- Red Line SI-1
- Techron Concentrate Plus
- 3M Max Strength Fuel System Cleaner #08814
- Royal Purple Max Atomizer 18000
- Gumout All-in-One (might be off list soon due to dropping levels of PEA)

 

Heya, Sorry for the delay i didnt get notifocation of replies.

so,
as i commute 300 odd miles a week on it, i regually go through tanks of fuel so i dont think its bad fuel in the system, as tank gets emptied/filled 3 times a week. bike is never left standing for more than 48hours at the weekend.

I replaced the aftermarket can with a stock can and no diffrence was made.
i had a garage replace the plugs and air filter and no diffrence
had fresh oil at the same time and no diffrence
the garage also checked for fault codes and nothing showing.

to be more precise after watching the rev counter it only happens at 7k. and lasts from 7000 to 8000rpm. after 8k it will then take off like a rocket. which causes other issues in low gears, as twice I've been caught out with the bike suddenly wheeling as if I've hit a powerband or something. it catches you off guard as it goes from no power to a bloody booster switch.

I had the garage check the system and no fault codes showed up. it had a new stock can fitted with no leaks, i also got the garage to fit new nkg plugs and an air filter.
the throttle position does not seem to make a diffrence, i've tried rolling off and back on and it makes no diffrence in the dead zone.

 

hi, did you find out what the issue was? I have the exact same issue at 7k revs, it just goes flat then goes like stink from 8k upwards. So far I’ve just changed the oil, but was going to swap out the air filter to see if that helps.

 

Yes,

For me it turned out to be the downpipes. I just lived with it until my downpipes got a crack. I replaced them with black widows and no more issues.