Downshifting Issue - Updated: It's back!

FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

Hey all,

Ok! I've recently had a few issues when downshifting. It doesn't happen all the time, and I've not found the commonality in the incidents but ... I've found that when I'm downshifting on my cbf125 I get this kind of whirring noise. It's loud enough that I hear it, and it's not a normal sound. It sounds likes it's coming from beneath me, and not from the tyres/brakes, but I can't see anything because I'm on the bike. Really freaks me out! heh. I think my chain may need tightening, but not much and oil etc all seem ok. It's only got 1600 on the clock. Any ideas?

Cheers

misscrabstick · Crazy Courier Joined: 05 Jul 2013 Karma :

Hmm hard to say , but I think getting the chain checked/adjusted is a good place to start, once that's been put right you'll know that if you still have a noise then it's not the chain.

FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

I would've thought if it had been the chain, it would happen every time i downshift, no? I'll get it adjusted later anyway.

Just thought I'd see if there were any other possibilities to check/change while i'm at it Smile

Thanks

stickybackbob · Trackday Trickster Joined: 23 Mar 2013 Karma :

This may be a daft question but have you checked your engine oil level lately?

CG Sam · Crazy Courier Joined: 08 Apr 2013 Karma :

My CG does this sometimes as well, I googled answers and nothing much came up so I decided to ignore is s it doesn't effect the bikes running
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P. · Red Rocket Joined: 14 Feb 2008 Karma :

Does it go away if you are in neutral and rolling, then holding clutch in and putting into first make the noise appear again?

Noticed my Vara does this, I just started wearing earphones. Laughing

FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

Thanks for the replies!

I'll double check my oil levels when I'm sorting my chain later!

The noise doesn't always appear, and never when i go up the gears. I always ride with one headphone in, which is why i was surprised i even noticed it!

CG Sam · Crazy Courier Joined: 08 Apr 2013 Karma :

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

hi fibob,

when it makes this noise, is it actually in gear in so much that it will drive the rear wheel or the rear wheel will "drive " the engine ????

or does it make the whurring noise and not be "in gear", ie no drive or overrun?? and maybe suddenly "jump" into gear........

does it make the noise when changing gear when its on the centre stand?? be carefull cos if it comes off the centre stand the bike will shooooooot forward and go thru a wall!!!!!!!! be carefull.

may be it is a bit difficult to get into gear on the down shift, do you blip the throttle when clutch lever is pulled and down shifts are made..........to make down shifts easier??

honda g/boxes can be a bit notchy......and clutch cable is in adjustment and well lubed?
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FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

Hey!

Ok, I haven't been able to sort the slack on my chain - I can't undo the damned bolt! Oil levels are good though.

Bikenut - the bike makes the noise when it's in gear, but i cannot replicate it. I do not know the conditions that cause it. It doesn't happen every time i downshift, and it's mainly when i'm going from fifth to third.

I'll try working it through on the centre stand later, and see if that helps wok out what the problem is.

I used to blip the throttle, but tbh it doesn't really make much difference as my revs don't move significantly when i downshift anyway.

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

from 5th to third?????

if you blip the throttle and "speed match " the engine speed to the expected speed in the lower gear, it may shift more easily, but remember that the dogs have to " engage" rather than "ride over each other"........

by dogs i mean......imagine a castle turret or tower, and see the castelations ( sticky upy downy bits ) ..........which mesh with each other and transmit the eng drive.........each gear will have its own dogs with which to engage........see cmnsl for your bike.........i presume the gear selector foot lever mech is all ok?? a pic would help for that.........
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garth · World Chat Champion Joined: 15 Dec 2004 Karma :

If it only does it downshifting I'm going to assume it's when you're on a closed throttle.

I'm going with chain tension.

trevor saxe-coburg-gotha · World Chat Champion Joined: 22 Nov 2012 Karma :

As long as the chain's not daft tight or mad slack it probably won't be that. Looking for about an inch and a half play, a bit more is better than a bit less. But for any noise to be heard, and especially a whirring - I dunno. Maybe a bit of "chattering" if it was really slack and fouling e.g. the centre stand (has the bike got a centre stand, even?).
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FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

P. · Red Rocket Joined: 14 Feb 2008 Karma :

Tighten that chain. 1 inch of movement is sufficient.

FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

trevor saxe-coburg-gotha · World Chat Champion Joined: 22 Nov 2012 Karma :

Keep us informed.
____________________
"Life is a sexually transmitted disease and the mortality rate is one hundred percent."

Mobylette Type 50 ---> Raleigh Grifter ---> Neval Minsk 125

FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

Update....

Never got round to tightening the chain yet. In fact not done anything to it yet, and the noise went and suddenly as it appeared. Very strange!!

ps I will get all my little amendments done, just because the noise has gone, doesn't mean she doesn't need a little service Smile

P. · Red Rocket Joined: 14 Feb 2008 Karma :

STILL not done the chain Laughing

FiBob · Nova Slayer Joined: 20 Jun 2013 Karma :

UPDATE:

The bike came back from it's service last week (2,500 mile service) so everything has been topped up, checked and tightened - but the noise is back!
Now it's not even when I downshift - all I have to do is slow down! Whether this be through letting the throttle out a little or braking. It normally disappears when I get down into second, but if I slow down to third and then pick up speed again it just continues until I slow right down.

Any ideas what this could be? Could it be because it's cold and the bike hasn't warmed up? My commute is only 12 minutes, so I don't know if it disappears on longer journeys.

thanks.

Pol Anorl · Banned Joined: 13 Apr 2010 Karma :

i get a whiring noise in 6th on my divvy it pisses me the hell off to the point i give up and just sit in 5th, stoopid gearbox.

check brakes?
bearings?

which side is it coming from
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