Mysterious clunk on throttle roll on -03 F4i

[soad]

Ok, SO! I need some help trying to figure this one out.

On my bike(2003 CBR600F4i, 43,xxx miles) there is a strange "clunk" that i get on throttle roll on. it happens in any gear, at all ranges of rpm. the higher the rpm, the more pronounced it is, too. no matter how slowly and smoothly i roll on the gas, it will always appear if i am coming from a no throttle situation.

my chain and sprockets are good, and properly lubed and adjusted, my cush drive is good. everyone i talked to said it was that so i replaced them. still there.

this clunk, it feels very...mechanical. like, there is too much clearance between two parts, and when i let off the throttle, the gap is too big. when i lay on the throttle, the gap closes very quickly, causing the clunk, and it lurches you. i took my bike to mid ohio last year, and it made me kind of scared a few times in the corners.

It's kind of like if you were cruising, and you pulled in the clutch and revved it up a little above your cruising rpm, and just dumped the clutch.

seeing as how i plan on hitting the track a lot more often this summer, this problem concerns me a lot. it is also very annoying riding on the street.

What could possibly cause this!?!

any help would be greatly appreciated, even thinking out loud. thanks!

[gsxr1000bill]

I know you said it was good but still.....chain!!!

[soad]

Explain this in detail.

Just describing the symptoms to friends that ride, several people said look into the cush drive in the wheel. I replaced them, but the old ones weren't even bad. hardly any wear on them. the problem did not change a bit, so it wasn't the cush drive.

[soad]

Also, my FI light is not on, so no codes. the FI light does work though. one time i forgot to plug in the IAT sensor after replacing my air filter, and it lit up.

[soad]

The chain and sprockets, although not brand new, show no excessive wear, and it is properly lubed and adjusted. that was my very first thought outside of "man i suck at throttle control!"

I figured since the FI light doubles as the CEL, it would be worth noting that theres no DTC's

[soad]

So far, I found ONE post on a stunt forum (F4i's are a very popular stuntbike) that mentions something about a pressure regulator being bad that could cause a problem like this. the OP in that thread replaced his throttle bodies with a used set and ended up with very similar problems. However there wasn't a response in the thread about it after it was posted.

any thoughts on that? or out of sync throttle bodies?

[soad]

Without the bike I can't help. Lima is more than 2 hours from my place. Good luck with your bike. At least it's winter.

this is true. thank you for your help, though. if i can't nail this down by spring, it'll be going somewhere for them to fix it.

[TSB67]

Has anyone else verified that this is actually abnormal?

[Pokey]

Change your chain and sprockets as well, keep it simple and stupid.

[bigd]

Has anyone else verified that this is actually abnormal?

If it's as described...it's abnormal. (at least it's not that way on a 2001 f4i)

[soad]

It is definitely abnormal. this clunk is pretty severe. enough to make my butthole clench on throttle roll on in a corner.

what say you guys about the culprit being a bad swingarm bearing?

[vf1000ride]

Easiest thing I can say to try and troubleshoot the problem is to get the bike up on a rear stand. Put the transmission in gear and then start rocking the rear tire back and forth by hand. Hopefully you will be able to reproduce the clunk and find out if it is inside the engine cases or if it's in the final drive. If it's not in the chain or final drive the next place to look is the pivot at the front of the swingarm. Make sure the bearings that the swingarm pivots on are still good. You can check that with a friend. You need to see if there is any side to side or front to back motion of the swing arm where it meets the motor. Basically somebody holds the bike steady and you try to wrestle the back tire. If the swingarm moves and the rest of the bike stays steady, you found it.

[Al Z. Heimer]

Easiest thing I can say to try and troubleshoot the problem is to get the bike up on a rear stand. Put the transmission in gear and then start rocking the rear tire back and forth by hand. Hopefully you will be able to reproduce the clunk and find out if it is inside the engine cases or if it's in the final drive. If it's not in the chain or final drive the next place to look is the pivot at the front of the swingarm. Make sure the bearings that the swingarm pivots on are still good. You can check that with a friend. You need to see if there is any side to side or front to back motion of the swing arm where it meets the motor. Basically somebody holds the bike steady and you try to wrestle the back tire. If the swingarm moves and the rest of the bike stays steady, you found it.

Do this for sure and also rock bike back and forth in gear on the ground not running of coarse to see if something comes up. I am leaning towards a gremlin in the ignition or fuel injection system. Sounds like it could be a momentary lapse in reason in one of the systems. This would cause all the slop in the drive system to go from a pull to coast to pull again. It would be like trying to accelerate and flipping the kill switch on and off. Which would explain the higher the rpm the harder the hit or clunk. Just a theory. Do a wiggle check with the wiring. Especially handle bar to frame where it all the movement is. Not sure if it has a tip over switch but it would be easy to bypass to eliminate as a cause. Do this with the bike running and listen for a miss in the engine.

[ReconRat]

Have you actually looked the frame over carefully for cracks or broken/loose frame members? All the motor mounts? Everything connecting the front wheel to the rear wheel.

Weight transfer will make a frame problem clunk pretty loudly, or a strong feeling of instability.

edit: a problem with carbs or injectors was a secondary choice.

Edited January 5, 2013 by ReconRat

[Hydrant]

I know its prolly not a clunk, but could it be something in the motor?

F4i's (mine included) were pretty well known for having the cam chain tensioner that would have a pretty distinct rattle around 4k rpm through 6-7k. I had mine replaced under warranty, but I know of some guys that put an adjustable tensioner on. Could it be cam chain is going slack then back under tension with the quick on / off throttle?

[TSB67]

I know its prolly not a clunk, but could it be something in the motor?

F4i's (mine included) were pretty well known for having the cam chain tensioner that would have a pretty distinct rattle around 4k rpm through 6-7k. I had mine replaced under warranty, but I know of some guys that put an adjustable tensioner on. Could it be cam chain is going slack then back under tension with the quick on / off throttle?

No.

[bshultz0930]

just curious.. did you actually roll remove the chain and roll each link by hand and make sure that none of them were stiff? i installed new tires on my bike earlier in the summer and when everything was back together, i too had a clunk sound only when rolling into the throttle.. but i didnt feel anything.. i did find though that as well as i maintained the chain, with 32,*** miles on it, there were a few links that were pretty stiff.. replaced the chain and sprockets and the noise went away.. just something to think about.

[Hydrant]

No.

No, what?

That the F4i doesn't have a CCT problem?

[soad]

No, what?

That the F4i doesn't have a CCT problem?

The F4i has the CCT problem, however my symptoms don't really point towards that being the problem.

This weekend is supposed to be warm, so I'm going to find some time to check all of these potential causes out hopefully. I'll get back to you guys and let you know how it went!

[Hydrant]

Gotcha.

I'm trying to think of on mine any other mysterious clunks or rattles and I'm coming up empty.

[soad]

OK SO! I checked the swingarm bearing by doing this:

Removed the rear wheel, and unbolted the bottom shock mount and removed the nut.

I did this under a covered parking space, and it has a large I-beam above it, so using two ratchet straps, I hoisted the rear of the bike up by the subframe(an F4i has this weird bar thing under the rear seat, it was easy and sturdy) and supported some of the bikes weight using a jack under the exhaust. It wasn't the sturdiest, but it works pretty well.

Then I jiggled the shit out of my swingarm every which way, and I couldn't get any play to occur.

So I do believe I ruled that one out. I ran out of daylight today, so tomorrow I will check my throttle cable, and fuel pressure regulator.

Also, I rode it around a tad, the clunk, it is also on throttle roll OFF as well as ON. It's just a lot more prevalent on throttle roll ON.

I don't think I mentioned this before, but i have a PCIII(non usb) and a Jardine RT-One slip on, and the map loaded on the PCIII is the one off the site for a f4i with a jardine rt-one and a K&N filter. however, the problem was still there when there was the stock map on it.

And for reference, here is a pic of my sprocket wear.

Edited January 12, 2013 by soad

[soad]

http://www.youtube.com/watch?v=w_EdGvjGIyo

That is my bike in first gear with the wheel off the ground, and me moving it back and forth. I am pretty sure that this is not supposed to happen, it even SOUNDS like the clunk. Any ideas?

Also, sorry for video quality, my camera is a potato.

[vf1000ride]

Have you taken the cover off the front sprocket and make sure that it is tight on the output shaft? Not sure on your bike how it is secured but if it has a big nut on it and that nut came loose. It could mean the clunking is the front sprocket wearing away at your output shaft.

[cOoTeR]

That is my bike in first gear with the wheel off the ground, and me moving it back and forth. I am pretty sure that this is not supposed to happen, it even SOUNDS like the clunk. Any ideas?

Also, sorry for video quality, my camera is a potato.

I think that is normal while the bike is in gear and you try moving it. But I would check to make sure the spocket isn't wiggling on the shaft. If its not rotating without the shaft moving is say that's fine.