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View Full Version : 2009 CB400 *weird* sound



Tenacious C
27-06-2011, 11:10 PM
I joined the Honda CB400 Legion a few months back and purchased a like-new recycled 2009 mod. Im L's so a really perfect bike to learn the road-riding trade but theres a thing that bugs me a little bit and Im hoping a fellow Legionaire can provide a few thoughts.
Start the bike and give a little stand-still throttle, sounds great, no rattle or tap's. Head out and slide through to a few streets and turns upto 3rd-4th without radical throttle, just 'warming up', sounds good, responds and handles fine.
THEN weird sound #1. Slowing down, say 4th back to 3rd or 2nd I detect this sound that is a little hard to describe. Nearly like the sound of air releasing from a pressured thing, not really metallic or quick "ping" like. You know in a car when you have something in your tire and every rotation you hear it, but on my bike its not every tire rotation but dependent on speed but not rev's. When I hear the sound Ill give the throttle a boot with clutch-in but the sound 'tempo' doesn't change but as slowing down so does the sound, and likewise while accelerating. But the sound is audible in 2nd/3rd, I dont think it exist's in 1st (perhaps too slow) nor in 4th upwards. Although after coming down from 6th / 110k's to 5th / 90k's I reckon there is a whistling sound (werid sound #2) I dont hear it while speeding upto 100+ but I do when coming down... strange.
Well maybe both sounds are normal? I dunno as Im new to the bike. I've done only 300k's since buying the bike and have noticed the 1st "low-mid" range air-release sound since I got it but only recently the "high" speed whistling sound (finally got my confidence upto to hit the highways!).
Would really like to hear some feedback from other CB400 riders.

bennjamin
27-06-2011, 11:13 PM
might be chain

too loose/tight/dry/over lubricated. which is slackened when decellerating...just an idea

Tenacious C
28-06-2011, 09:00 AM
Nah, definately not chain. Would expect that to be a constant and more metallic sound. Anyways, checked the chain and tension is pretty much spot on.

bennjamin
29-06-2011, 06:31 AM
Checked the rear gasket/ring clamp where the exhaust connects to ymthe muffler ? Might be loose/ too tight ? Checked oil level ?- low will give more obvious transmission whine in the first 3 gears too

Tenacious C
30-06-2011, 01:18 PM
Thanks for the advice, I have checked the chain recently and tension is fine, no kinks and well lubed.
If the sound is related to moving parts, I dunno which one...
Someone suggested air-filter? Could it be possible that a ill-fitting air-filter could be responsible for air-suction sounds?

bennjamin
30-06-2011, 07:04 PM
Thanks for the advice, I have checked the chain recently and tension is fine, no kinks and well lubed.
If the sound is related to moving parts, I dunno which one...
Someone suggested air-filter? Could it be possible that a ill-fitting air-filter could be responsible for air-suction sounds?

yeah ofcourse it can - IF it is ill fitting tho , there would be other issues such as the airbox not fitting properly , and ultimately the tank not fitting properly. Something that would be noticeable. Tell us this
Is the noise directly relative to engine revs ? IE sound gets louder higher revs ?
And , is the noise directly relative to engaged in gear or neutral ? IE same noise at same RPM , in gear and not in gear etc ?

Tenacious C
02-07-2011, 12:28 AM
Noise is not related to rev and not related to having gear engaged or not... just to baffle things futher!
But I reckon I might have received some advice that is close to the mark. Front brakes. Could very well be a combo of air-flow around the slotted disc and / or pad's slightly rubbing the disc. Tomorrow Ill take it out and if I get the sound Ill try squeezing the front brakes and see if the sound remains.

Tenacious C
27-07-2011, 03:08 PM
Quick update, sound was from slight scrape on the front rotor/s from brake pad. Appears that if I use front brake while handlebars are turned to left then the *weird* sound is audible. Fixed with a quick nudge on the brake lever.
No biggie, thanks for all contributions.