TommyMiller

I have a 2002 cbr f4i. It has a two brothers full exhaust. It starts up and runs fine. The problem is that most of the time when I start off from a stop, the bike tends to sort of bog down for a few seconds. After the initial start up bogging it accelerates at a normal pace. It performs normally throughout the remaining gears. Although the bogging does not occur every time, it definitely takes place during the vast majority of starts. It almost feels like I am trying to get the bike moving but I am in a higher gear than I should be. I have done some research and have found a few others with similar issues but no real solutions. Any help would be much appreciated. Thanks.

theedeadmau5

power commander?

Kusai.Nihonjin.Desu

Where does your idle sit?

TommyMiller

Thank you for your replies. I do not have a power commander on the bike. Do you think that would help? Not sure if this helps or not but it seems to do fine when there is no load on the motor. i.e. when it is in neutral and I rev it up.

As far as where it sits at idle, it seems normal. It sits at right about 1000.

Again, thank you for the help.

theedeadmau5

since you have an upgraded exhaust on a bike where the fuel/air combination may be a little screwed up in the first place, the f4 was honda's first full FI bike put into production, you may need a power commander with a solid map to correct any rich/lean conditions you may be experiencing. your bike is acting weird because the bike is tuned for the factory exhaust and when the aftermarket exhaust was installed the fuel/air mixture was thrown out of sync. first you should make sure your injectors are pumping at 50 psi before you do anything because the cost of the PC and the map can run you over $500 and if they arent pumping at 50 psi then you have an underlying issue with the injectors themselves that needs to be addressed first. if you're at 50 then the power commander should be your next step, and if mapped correctly with the exhaust that you have installed it will correct the fuel/air mixture thus giving you a smoother response from the throttle.

google bike dynos in your area and give them a call for pricing on their mapping charges.

TommyMiller

Ok those will be my next steps. Thank you for the help.

rd91sib18c5r

Your idle is a little low should be 1300, you can adjust it easy. These bikes are pretty
guttless under 5k so if your under that rpm there isn't much power. You can regear it
that would help alot but you wont be able to go over 150,lol who needs to go that
fast anyway lol.

TommyMiller

Yea, the lack of power below 5k is pretty annoying. I do not think that is the cause of the bogging as it does not occur all the time. It seems more like a fuel issue. Does my bike have more than one temp sensor? Maybe one is malfunctioning causing the bike to think it needs more fuel than it does. Like it would need more fuel if it was a cold morning and was just started. The temp display reads between 175 and 225 Fahrenheit depending on whether or not I am sitting in traffic. Maybe the temp the cpu is reading is wrong. Just a thought. Does that sound reasonable? Thanks

rd91sib18c5r

How many miles are on it? have you changed the spark plugs?

Kusai.Nihonjin.Desu

Give the idle screw a little cranking, and see where that takes you.

I second the notion to check the gaps in your spark plugs, but I don't think that would give you problems just in first gear from a stop.

Probably don't want to hear this, but maybe it's the riding technique.

TommyMiller

I recently purchased the bike and it has about 8k miles on it right now. I have not checked the spark plugs yet but will do so soon. I will also adjust the idle screw in order to raise the RPMs at idle a little bit. Hopefully it is my riding technique. This is my first street bike although I have ridden dirt bikes for quite some time. Maybe it is just the way I am releasing the clutch? Thanks for the help.

Shogun_35

Sounds like a power commander is in order. Just ask any single person who ever put a full system on a carb'd bike without a jet kit. Same thing. Gotta have it. Probably be cheaper to buy a used stock header and run the slip on if you can. No tuning required for slip on's. Still a good idea to check plug gap and airfilter. Simple stuff but if there not in good condition it will run a little crappy.

theedeadmau5

this bike isnt carbed

sparse_undergro

I hope anyone doesn't mind me signing up to post my two pence worth.
I bought a Honda CBR600F4i or Honda CBR600FS2, which had been sat around for two years without being used.
I brought it back home in a van and soon started to uncover a history of faults with the bike.
A complete non-starter as you would guess. New battery revealed the fuel pump to be faulty, chewed ignition wires and a stuck ignition barrel. ACF50 cleaned up the barrel and I soldered new connections for the wires and cleaned up each electrical block as I went along.
New fuel pump and new filter worked a treat but the bike still wouldn't start...
Now onto the injectors - cleaned, tested and replaced.
Spark plugs - corroded and rusted so those were replaced. The bike finally started with a huge amount of black/brown/grey smoke as you can imagine!

The coolant was flushed, fairing bolts drilled and replaced, oil and filter changed over along with a front tire and the bike was ready for the road.
Problems - rattling from the exhaust (turned out to be metal dislodged in the manifold)
AND
the bike was bogging down under load - big time! Cold/Hot/Humid. The fuel was super unleaded and the tank had been flushed along with the lines, filter, injectors.
NO FAULT LIGHTS.
Fuel pressure regulator checked and in order. Minimum fuel flow checked and in order. Injectors in order. Spark plugs in order and correctly gapped.

Cam chain tensioner changed over made no difference and a new K&N Air Filter changed which made no difference either.

The symptoms were - driving at normal road speeds in normal conditions. The bike would lag horrendously below 4000rpm and would have a significant notch of acceleration at 8000rpm but no where near what I've experienced before. At 8000rpm and above the bike was a dream. Anything below was a nightmare. Town driving was hellish - at least more than usual.
Also a significant bogging or bog would be felt at wide open throttle (WOT). The bike is injection and the ECU is in good order. No power commander. Standard Exhaust. I had also synchronized the throttle bodies, checked the throttle position sensor and the MAP sensor. YouTube those to give you a good idea of what you're doing. The air temp sensor was also working.

I took the bike to Scotland on a tour from the South East and it was fantastic. If you're in the UK and you haven't ridden to Scotland then you're missing out!! But the bike wasn't improving. 99RON fuel or 91RON fuel didn't make a difference.

On returning home the last item on my hit list was the valve clearances. What an absolute butt ache. More of a butt ache than doing 1700miles in the last four days!
If I'm honest I was dreading it BUT i'm now 100% confident in saying VALVE CLEARANCES ARE THE FIRST THING YOU SHOULD BE DOING AND THEY'RE VERY IMPORTANT!!
Plus it wasn't that bad doing the job. If you're good at spannering then crack on. Stop getting freaked out by forums and YouTube videos and get yourself a Haynes guide and crack on. Getting the cams back in and correctly aligned was a doddle - that was the bit I was stressing about the most.

What can I say - a completely different bike. My only hope is that you've come across this post and despite knowing that its a long and sometimes expensive job to alter you valve clearances - it was well worth it. By the way don't forget to sync your throttle bodies again.

For anyone who maybe interested - ALL of the clearances were out. Some met the lower edge of what would be 'ok' but that wasn't enough for me. I'm not after an old dog to be perfect but the best it could be. The valve shims ended up costing me £30 after moving most of the shims about, a new gasket for the cam chain tensioner and lots of my time and patience.

Stop reading and start planning when you're next going to get it done. It's really not that hard once you know how and I wish you the best of luck. If only I had come across this information in the beginning I would have been much happier. The bike now performs like it should. I had been ranting, raving and swearing at it before. It's a plush ride with plenty of poke, wizz and jizz. Smooth across the entire rev range with NO MORE BOGGING DOWN. I can even safely say that the 'every CBR does that below 4000rpm' is complete horse.
My answer is - they don't all do that. They're just the ones that haven't had their valve clearances altered yet.