CBR250RR knocking sound at low revs

**Akzle** · 28th November 2012, 06:24

Originally Posted by 0li123

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

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

rebuild time!

**p.dath** · 28th November 2012, 06:45

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** · 28th November 2012, 08:32

Originally Posted by 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.

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

seriously - check the underseat storeage for midget occupancy

**ducatilover** · 28th November 2012, 09:18

Originally Posted by 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.

$100 says it isn't

**p.dath** · 28th November 2012, 12:16

Originally Posted by ducatilover

$100 says it isn't

Haha. Doh.

**FROSTY:Me** · 28th November 2012, 15:18

Originally Posted by FJRider

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** · 28th November 2012, 18:17

Originally Posted by FROSTY

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.

Originally Posted by 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.

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:Me** · 28th November 2012, 19:07

Originally Posted by FJRider

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-** · 28th November 2012, 19:17

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** · 28th November 2012, 20:01

Originally Posted by 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.

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** · 28th November 2012, 20:11

Originally Posted by 0li123

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** · 29th November 2012, 05:35

Originally Posted by 0li123

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** · 29th November 2012, 16:51

Originally Posted by Akzle

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-** · 29th November 2012, 17:21

Originally Posted by 0li123

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.