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Hi everyone, i searched high and low for help on many forums and had no luck, so im really hoping someone here can point me in the right direction.

I recently purchased a 1994 CBR 900RR for 1300.00 and im having a weird problem with it.

When i fire it up first thing in the morning i hear a quite noticeable knocking sound coming from what seems to be the upper part of the engine.

If i push the clutch in, it seems to go away. Or, if i just wait until the bike warms up, the idle raises and smooths out, it seems to go away as well.

It only seems to happen in the AM or when the bike has been sitting many hours at a time. If i fire it up and let it warm until the knocking goes away i can come back 1,2,3,4 etc. . hours later, start it and it cant be heard.

if you can give me clues or point me in the right direction, i would greatly appreciate it.
 

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Hello Cage - same problem that happens with cars , very basically it takes a min of so until the oil reaches the top end of the motor (especially when oil is cold and thicker) once the oil gets under the lifters the sound will goes away - you can go spend some money and get the lifters adjusted , but not really worth it. This is of coarse presuming that the knocking noise you mention is a slight knock and not a heavy knocking sound (almost like a ticking sound )


Hope this helps

Boc
 

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its a pretty loud knock, i mean, you dont have to listen hard at all to hear it.
 

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Hey ! may be a long shot but is there any chance you can record the sound and then post it on the net -- if we can hear it -- it will be really obvious as to what the noise is - at this stage i am just second guessing with the info you have given

Boc
 

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I started the bike up this morning, so i probably wont be able to replicate the problem today, but ill try to get a sound clip tomorrow morning so you guys can hear it for yourself.

from the responses i have gotten here and at othere sites. . these are all the posibilities i have heard so far.

- need thicker oil

- dont worry about it, oil just havent circulated yet and the cold makes the knock sound louder


- Cam Chain Tensioner needs replaced

- simple, you need a valve adjustment

- 900RRs are just notoriously noisy, i wouldnt worry about it

- could be carbon build up

- could be the transmission if you say it goes away when the clutch is pressed in. .

as you can see, thats alot of possibilities and im just trying to narrow them down lol

anywho, ill get an audio clip
 

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It's normal cold engine noise. The 900rr does this. It's when the noise does not go away when you should worry ;)

Does the engine make any "bad" sounds when you drive it up to 10,000 rpm and then let off the throttle? If it does then check the cam chain tensioner lifter. That's about one of the few things that do go bad on these engines.

The cold engine noises your hearing are: the carb slides rattling, the valves, shims, and buckets have not reached operating temperature yet. When engine parts heat up they expand a tiny amount and then the noise disappears. Very little of that noise is from a lack of oil, maybe the first 10 seconds, these engines have an awesome oiling system. It's queit ingenious how it lubes the top end.
 

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o.k. heres an update, and its not good :(

I decided to take the bike out to see if i could hear it knock in higher RPM's. No knock, but it sputtered, oil light came on, and it just died on me.

I checked the oil and it was a little low, but still had some in there. I walked to the store and got more oil to throw in. It started up, the oil light went off. I got it a couple more blocks, it sputtered and shut down on me again. The temperature guage only went 1/4 of the way up so it dont look like it was running too hot. But now it wont start. Think this problem is contributed to the knock i heard? Or could it just be the carbs need rebuilt or cleaned?
 

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You said the knock goes away once the engine gets up to temperature correct? A bad engine knock never goes away. I'd say if the knock sound goes away the problem is probably fuel or electrical related.

edit: The way you are decribing it the bike is either starving for fuel, or is out or almost out of fuel.
 

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looks like the carbs are the culprit. . ill work on rebuilding them this week and see if my problems start to go away
 

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if you are saying that the clutch is engaged and the knocking noise goes off, its a badly worn clutch basket. but no matter how bad the basket wears out... it will not contribute to the engine sputtering/dying off.
 

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if you are saying that the clutch is engaged and the knocking noise goes off, its a badly worn clutch basket. but no matter how bad the basket wears out... it will not contribute to the engine sputtering/dying off.
it may have a worn clutch basket, but if it is i believe its a separate issue than what was causing the the bike to stutter and cut off on me.
 

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this by the way you discribe it sounds more like piston slap,a mild knock sound which gets less noticable as the engine heats up and the pistons expand,this is definatly not an electrical problem or fuel related.just my .02$
 

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I agree with cwr954. Piston slap usually occurrs after the engine has overheated at some point. The piston gets so hot that when it cools down it reduces to a smaller than original size then expands when the engine gets warm again and the noise vanishes. Unfortunately only one fix....replace pistons. This should not stop the engine unless it is starting to sieze. good luck
 

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hey, i have a 93 blade and i have the same thing happening with mine, at low revs when cold it makes a loud knocking noise. low revs being under 1k
 

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Hi everyone, i searched high and low for help on many forums and had no luck, so im really hoping someone here can point me in the right direction.

I recently purchased a 1994 CBR 900RR for 1300.00 and im having a weird problem with it.

When i fire it up first thing in the morning i hear a quite noticeable knocking sound coming from what seems to be the upper part of the engine.

If i push the clutch in, it seems to go away. Or, if i just wait until the bike warms up, the idle raises and smooths out, it seems to go away as well.

It only seems to happen in the AM or when the bike has been sitting many hours at a time. If i fire it up and let it warm until the knocking goes away i can come back 1,2,3,4 etc. . hours later, start it and it cant be heard.

if you can give me clues or point me in the right direction, i would greatly appreciate it.
Happens to me 2 on my f3 but not loud I d K...
 

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it may have a worn clutch basket, but if it is i believe its a separate issue than what was causing the the bike to stutter and cut off on me.
if the engine stutters and cuts off so frequently (after 3-4 minutes when the engine is started from cold) try checking the valve clearances.
i'd recommend u replace the intake valves + shims + valve seals. the valves are probably laden with carbon. then clean the carb and do a carb synchro, and drop in a new set of plugs. i'm very confident u'll love the bike after its done, taking into count u have good condition clutch plates, clutch baskets, timing chain, and not worn piston rings.

costs some money, but its worth every single cent spent at the end of the day.
 
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