CBR250RR knocking sound at low revs

[0li123]

I have a 1992 CBR250RR,

Just recently I have noticed a faint knocking sound coming from the engine at low revs, between 2000-5000 I have only noticed it in gears 1,2 and 3 but I think this is just because these are the only gears that I use within this range. It doesn't seem to have any effect on the performance of the bike but surely cant be a good thing. If anyone has any ideas what might be wrong please let me know, id greatly appreciate it.

Cheers

[Akzle]

I have a 1992 CBR250RR,

Just recently I have noticed a faint knocking sound coming from the engine at low revs, between 2000-5000


i'd say it's definitely a knocking noise in the engine.



ps. check chain tension.
could be piston slap, could be big end bearing going, could be no problem.

[0li123]

i'd say it's definitely a knocking noise in the engine.



ps. check chain tension.
could be piston slap, could be big end bearing going, could be no problem.

it doesn't make the sound when stationary and idling, only when I am taking of or at very low speeds, so does that rule out piston slap?

[Akzle]

it doesn't make the sound when stationary and idling, only when I am taking of or at very low speeds, so does that rule out piston slap?

via the awesome powers of the internet, i can tell you for sure, that you have a honda.

and unless you're lying, i can tell you for sure, that there's a knocking noise happenin with the engine.

it doesn't rule out piston slap. or anything else.
did you check the chain?

[0li123]

via the awesome powers of the internet, i can tell you for sure, that you have a honda.

and unless you're lying, i can tell you for sure, that there's a knocking noise happenin with the engine.

it doesn't rule out piston slap. or anything else.
did you check the chain?

Yes I have a Honda and yes I have a knocking noise happening with the engine. I have checked the chain and I think it could do with a tighten and a lube.. I Have had a couple of big rides equalling about 2000 km since I last tightened it so would probably be a good place to start

[FJRider]

Yes I have a Honda and yes I have a knocking noise happening with the engine. I have checked the chain and I think it could do with a tighten and a lube.. I Have had a couple of big rides equalling about 2000 km since I last tightened it so would probably be a good place to start

Forget the chain. Sort the knock out first. A well lubed chain won't fix that on the side of the road.

You will hear the knocking sound as power is applied. (won't hear it at idle as no power is being applied)

As for what it is ... revving an engine to 19,000 rpm wont help it's longevity ... for long. Things wear out ... tolerances get excessive ... bearings fail ... gudgeon pin wears ...

Bluntly ... everything inside the engine casings get loose. Later on ... something lets go.

Take a guess what actually lets go. Everybody else will ... but keep riding it ... and we'll see who's right.

[FJRider]

Oh and MY guess is main bearings ... :beer:

[Akzle]

well OP, now you met our resident-retard FJ.

as some kind of lesser mortal, i don't expect you to be able to identify what the noise is or where it's coming from.
noise of the chain jumping the sprocket will be transmitted through the entire gearbox/case/engine.

how many kms has the bike done?

[Asher]

Try answering "who's there" everytime it does it, eventually it will get so annoyed by you it will throw a big end bearing in protest.


The obvious way to check if its the chain or not is if it does it with the clutch in. Or take a fairing off and hold your hand over the top and bottom of the cylinder and try and feel where the knock is coming from.

[Paul in NZ]

I have a 1992 CBR250RR,

Just recently I have noticed a faint knocking sound coming from the engine at low revs, between 2000-5000 I have only noticed it in gears 1,2 and 3 but I think this is just because these are the only gears that I use within this range. It doesn't seem to have any effect on the performance of the bike but surely cant be a good thing. If anyone has any ideas what might be wrong please let me know, id greatly appreciate it.

Cheers

Does the knocking sound happen when you are applying throttle to the engine and go away when you are on the over run?

If its just a sound it can be pre ignition or pinking but if its a vibration it may be something as simple as a loose engine mount etc.

[ducatilover]

Ride it to Te Puke and I'll have a look at it for you :niceone:

I would:
Check, adjust, lube chain.
Check for play on the output shaft
Check the clutch hub and bearing.
Check the steering head bearings
Check for end float on the crank (if it has any, you'd certainly know about it)
Listen for valve noise
Carbs out of sync can make some interesting noises too
Drop the oil and pick up screen and check for sneaky little bearings floating around...

If you're getting piston slap you'll have a fair amount of blow by on a cold leakdown test



Fortunately we can rule out cam chains as it hasn't got one and a stripped tooth on one of the gears doesn't seem to happen

[Fast Eddie]

is there a midget in the underseat storeage compartment? I had one on my 89 cbr250r and he made a hell of a knocking noise until I let him out..

[Akzle]

geez guys. you took long enough. i thought i's gonna have to carry this one by myself... :niceone:

[ducatilover]

geez guys. you took long enough. i thought i's gonna have to carry this one by myself... :niceone:
You could have solved it with all that solid advice you were giving

I know that it's a Honda now and the knocking is his heart beating for his boyfriend

[0li123]

Ride it to Te Puke and I'll have a look at it for you :niceone:

I would:
Check, adjust, lube chain.
Check for play on the output shaft
Check the clutch hub and bearing.
Check the steering head bearings
Check for end float on the crank (if it has any, you'd certainly know about it)
Listen for valve noise
Carbs out of sync can make some interesting noises too
Drop the oil and pick up screen and check for sneaky little bearings floating around...

If you're getting piston slap you'll have a fair amount of blow by on a cold leakdown test



Fortunately we can rule out cam chains as it hasn't got one and a stripped tooth on one of the gears doesn't seem to happen
Buger, thats where I was this weekend and where I first heard the knock, oh well.. it seems a little temperamental as I rode to work today and didn't hear a thing. I will try and check as many of these as I can but im not to sure how far I will get, but thanks for the input. the bike has done 44000km by the way

[Akzle]

...the bike has done 44000km by the way

44k isn't much. but it has probably been thrashed.

rebuild time!

[p.dath]

I'm going to put my money on it needing a new cam chain and tensioner.

Go to You Tube and search for motorcycle cam chain rattle, and see if your sounds like that.

[Fast Eddie]

I'm going to put my money on it needing a new cam chain and tensioner.

Go to You Tube and search for motorcycle cam chain rattle, and see if your sounds like that.

dumbass, cbr250's don't have a cam chain, gear driven cams.

seriously - check the underseat storeage for midget occupancy

[ducatilover]

I'm going to put my money on it needing a new cam chain and tensioner.

Go to You Tube and search for motorcycle cam chain rattle, and see if your sounds like that.
:bleh: $100 says it isn't

[p.dath]

:bleh: $100 says it isn't

Haha. Doh.

[FROSTY]

Forget the chain. Sort the knock out first. A well lubed chain won't fix that on the side of the road.
Hey mon cool ya jets ffor a moment. NO noise in neutral. Noise heard at XXX rpm whilst riding.
Think about it --the SIMPLEST solution is that the chain is just loose. Has a tight spot or maybee theres a hooked sprocket tooth.
Im NOT saying that this IS whats wrong but why not check the simplest stuff first.

[FJRider]

Hey mon cool ya jets ffor a moment. NO noise in neutral. Noise heard at XXX rpm whilst riding.
Think about it --the SIMPLEST solution is that the chain is just loose. Has a tight spot or maybee theres a hooked sprocket tooth.
Im NOT saying that this IS whats wrong but why not check the simplest stuff first.

To quote the OP in the first post.


I have a 1992 CBR250RR,

Just recently I have noticed a faint knocking sound coming from the engine at low revs, between 2000-5000 I have only noticed it in gears 1,2 and 3 but I think this is just because these are the only gears that I use within this range.

At low rev's (on a bike that rev's to 19,000 RPM) you should be able to tell the difference between chain noise and engine noise.

[FROSTY]

To quote the OP in the first post.
At low rev's (on a bike that rev's to 19,000 RPM) you should be able to tell the difference between chain noise and engine noise.
Maybee YOU or I would but by the very nature of a 250 rider they don't have the years of experience we have.Keep in mind too that the engine area of a cbr250 is well wrapped up in plastic fairings.-2 seconds to check a knackered front sprocket or a tight spot

[Dave-]

if you pull the clutch in while moving does it keep knocking?

what we want to know is whether the knocking speeds up with the engine or the speed of the bike.

if you can lift the rear wheel off the ground and spin it (you can pivot it on the side stand and get a friend to spin the rear wheel) does it knock? while you're at it check for slop in the wheel bearings.

do the same for the front.

[0li123]

if you pull the clutch in while moving does it keep knocking?

what we want to know is whether the knocking speeds up with the engine or the speed of the bike.

if you can lift the rear wheel off the ground and spin it (you can pivot it on the side stand and get a friend to spin the rear wheel) does it knock? while you're at it check for slop in the wheel bearings.

do the same for the front.

No im pretty sure it does not so would this indicate that it is to do with the engine and not the chain? probably not as clean and simple as that but oh well just trying to get my head around the issue. what would the fact that it does not happen every time I ride it mean? I will get onto that test to by the way, thanks.

[FJRider]

No im pretty sure it does not so would this indicate that it is to do with the engine and not the chain? probably not as clean and simple as that but oh well just trying to get my head around the issue. what would the fact that it does not happen every time I ride it mean? I will get onto that test to by the way, thanks.

Going up a hill in a higher gear (lower rev's) ... and opening the throttle ... and loading the engine (without a speed or rev increase) will usually show a knock .. if there is one.

Going downwind (at the same speed as the wind) is the time you hear lots of noises that you've never heard before.

[Akzle]

what would the fact that it does not happen every time I ride it mean? I will get onto that test to by the way, thanks.

that it probably isn't much to worry about right now.
(is it the difference between cold start and warm engine?)

engines make noise. it's what they do.

[0li123]

that it probably isn't much to worry about right now.
(is it the difference between cold start and warm engine?)

engines make noise. it's what they do.

yeah fingers crossed that its nothing. but nah first time I noticed it the bike was actually pretty hot and hasnt done it on any occasion when im leaving home at 5.30 in the morning so cold start does not seem to effect it.

[Dave-]

No im pretty sure it does not so would this indicate that it is to do with the engine and not the chain? probably not as clean and simple as that but oh well just trying to get my head around the issue. what would the fact that it does not happen every time I ride it mean? I will get onto that test to by the way, thanks.

or the gearbox.

[GrayWolf]

Done 44,000km's??

Who's gonna open the book on it reaching 45,000km's??? :corn:

[ducatilover]

yeah fingers crossed that its nothing. but nah first time I noticed it the bike was actually pretty hot and hasnt done it on any occasion when im leaving home at 5.30 in the morning so cold start does not seem to effect it.
If it was hot, check your plugs, hell, replace them (CR9E from memory)

[0li123]

If it was hot, check your plugs, hell, replace them (CR9E from memory)

I was thinking of doing that anyway, who would faulty plugs cause that noise?

[ducatilover]

I was thinking of doing that anyway, who would faulty plugs cause that noise?
Pre-ignition on a fucking hot plug :niceone:

[Akzle]

Pre-ignition on a fucking hot plug :niceone:

which brings me back to point Z. - use premium fuel.

[ducatilover]

which brings me back to point Z. - use premium fuel.
And the right plugs. And condoms.

[Akzle]

And the right plugs. And condoms.

never really believed in em.
which i suppose is why my bike runs rough and i have kids.

[ducatilover]

never really believed in em.
which i suppose is why my bike runs rough and i have kids.
:msn-wink: Opposite for me

[Askor]

I wonder if OP ever found the solution..

This made me piss my pants



never really believed in em.
which i suppose is why my bike runs rough and i have kids.