Engine knocking at idle when hot!!!

harperm · 07-21-2008, 12:37 PM

Hello everybody! First of all, allow me to introduce myself. Mark's the name, and I have just bought m'self a CBR600F4 (F-X for us Europeans). Now, I have utterly fallen in love with the bike, but it has started to make a rather alarming knocking noise when idle. It is totally quiet and sweet when it is cold, and even during warm-up, but after a good run, when I pull up at lights I can hear and feel through the grips a knocking coming from the engine. It idles at around 1200 rpm, and I will get about 4 knocks a second. If I rev the engine to about 3000 rpm, the knocks speed up with the engine, then disappear, possibly drowned out with the engine noise. If whilst stationary, I put it in first gear, hold the brakes on and very gently allow the clutch out to just biting point, but without applying any throttle the revs drop to about 900rpm, and the knocking goes away. Basically, if the eninge is under any sort of load, even very light, there is no knocking, but as soon as you roll off the throttle, the kncoking noise comes back, and is consistent with the engine speed. Makes no difference in-gear or clutch in or out, but it does seem to be eminating from the lower rear of the engine, say around the moutning joint where the rear shock sits, perhaps around the gear change lever even.

I have searched far and wide for an explanation, but as yet I have found none. I will say it is a medium knocking, and not a rattle, the same sort of sound if you lightly knocked on a car window with one of your knuckles, but as I say, disappears as soon as yoiu pull away.

Ideas, or theories are very wlecome, and I am sure this will be an interesting thread.

Thanks all, and I really look forward to keeping in touch via the forum (with happier tales)

Desert Blade · 07-21-2008, 1:35 PM

Knocks at idle, gets bad at mid range and dissapears with higher revs? Could it be your cam chain tenchioner lifter? Its a rather common F4 problem. Unless of course you have oil light flicker or anything like that. Then it could be something REALLY bad.

Fox

harperm · 07-22-2008, 6:03 AM

Well, it dissapears really after 3000rpm (audiably anyway). It seems to pull ok, even in mid-range, but I am new to this particular bike, so my judgement is worth a gnat's knee.

Red Rider · 07-22-2008, 8:17 AM

dark4ce · 08-25-2008, 8:16 AM

Hi there, i too poses a honda cbr600 f4 (2000 model) and have the same problem. I don't think it's the CCT cause i had it replaced for about ..4-5 months ago (from then on, i only drove for about 5000km)... i remember i had the knocking when the CCT was damaged, changed the CCT, the ratling sound of the chain went away, but the knocking remained...

Now i have another problem, a vibration somewhere at 3000 revs ..at 5000 it goes away and comes back in power at 6000 while slowely disapearing at 7-8000 revs (probably the road and engine's vibration cancells it out)..i've visited a mechanic and he said it's the clutch..told me to buy some parts..made an order,the parts will arrive in about 3 weeks ...if the knoking goes away with the vibration,i'll keep you posted...

What i'm most afraid is that the knoking comes from the CRANKSHAFT /PISTON assembly... and that's a bugger

ReDevil · 08-26-2008, 11:02 AM

can it be the valves not sitting properly in the seat when it idles, this would generally go away with higher revs. I have a GPX250 with the rocker and that generally gives a knocking / tapping noise when the adjustment goes wanker.. not sure how the F4 has adjustments to the valves.

dark4ce · 08-26-2008, 11:08 AM

in my case it certantly isn't the valves making the sound, its a verry strong knocking sound... i know how the valves sound like and it's not that..it's something massive... and the sound comes only when the engine is hot... by that time, the valve pills are hot (they're volume increases) and usually, the taping sounds of the valves goes away ...

harperm · 10-01-2008, 12:24 PM

Right, had the CCT replaced, and no different. It is comming from the bottom of the engine, and it is obvious the noise if eminating from the bottom end of the crank assembly. Imagine lightly tapping the engine casing with a hammer two or three times a second and you get some idea of the noise. I can even feel this being transmitted throught the handlebar grips.

auh · 10-22-2008, 6:13 AM

I'm having this exact same problem on my F3. I recently changed the oil but I'm going to do it again and put some of that motor flush through it to make sure none of my oil passages are clogged.

If anyone else knows anything though I'd love to also find an answer to this problem...