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Discussion Starter · #1 ·
The last few days I've had a rattling noise while engine breaking on my 300F. It's kinda loud and sometimes sounds somewhat squeaky. When I press my hand on the front of the tank or on the plastic shroud the noise would go away. I took off the fairings and made sure the front tank bolt was tight, I also tightened down the side fairing support bolts. Everything seems tight near the front wheel (reflectors, etc). I figure its something under the tank or attached to it.

Any ideas? Is this something worth taking to the dealer? I'm under warranty still...
 

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It sounds like the infamous fuel cap rattle.
You can trawl through the screeds of previous posts about this at your leisure if you wish, but cut yourself a good lunch first :laugh:
 

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same problem, only happens when im creeping or going over bumps....

not the fuel cap, although the fuel cap contributes sometimes...it has its own rattle.

been driving me crazy, it comes, then goes, then comes back and disappears again....sounds like coins in a plastic cup.

imo its originating from inside the tank.

will be dissecting in a few days
 

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I don't think it is related but when I heard a rattle that sounded like it comes from the tank on my bike, you know my rubber cargo strap under the seat that holds manual and insurance card, it came off twice by itself and makes a huge racket. I can't understand how it happens it is tough to stretch it back over.
 

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This might be the same rattle on my 300F I have mentioned, but I can't find it. I even coasted down a hill with the engine off and I can still hear my rattle when I go over a little rough road. Mine sounds more like a BB inside a tin cup. Someone on another forum suggested it might be the BAS...the safety mechanism behind the light that shuts the bike off when the bike is not upright. Apparently there is a BB or something inside that switch. He said it rattles like a BB which makes me think that might be my rattle too. There is a YouTube video of how to bypass the part, but it is a safety mechanism, so all I want to do is find out if that's it. I don't have my service manual yet and I could not get the nose cone off to see the part...got it loose, but I was either missing a fastener, clip or something cause I couldn't get it off. When I get my manual, it's the first thing I am going to check. I can't rule out something inside the gas tank either, but mine does sound a farther forward of the tank. You have to know some Honda engineer KNOWS what we are likely experiencing, but would never speak up. Oh yes, I should mention I had a flapping noise when I was off throttle...different noise and that was due to detonation and solved immediately when I filled with premium gas which is all I now use in this bike. It shouldn't take premium gas, but mine needs it.
 

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what your talking about is the drop sensor, i thought about that as well. It can be removed and the bike will still run.

anyway, im dissecting this ***** tomorrow and getting to the bottom of it. Driving me nuts.
 

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Let us know what you find. I don't have a loose gas cap or any loose fasteners and can't push anywhere to get my rattle to stop like some people. The radiator is down there too and it could even be something related to that...something rattling around. Mine is also not 100% of the time...but it's more like 80% and it just started a couple weeks ago. I've tried moving and shaking the bike to try and produce the sound but that doesn't produce it, so it may not be something in the gas tank cause it seems like you could hear that by bouncing or moving the bike from side to side and you can't. The fact it rattles just coasting in N with the engine off seems significant, but even without a helmet I can't locate the darn rattle.
 

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Discussion Starter · #9 ·
I have a rattle when I apply the rear brake! I read that it might be the brake pad moving around in the caliper and there are a few ways to remedy it. It doesn't bother me as much when I know where it's coming from and that my bike isn't going to have an issue.
 

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My rattle sounds like the same rattle KRS1 has. I suppose we could be talking about different things. For sure mine is coming from somewhere up front. I don't see how a brake pad could be making my sound which sounds like a small metal item bouncing around on plastic, like something could be inside the nose cone. I can't rule out anything coming from the instrument panel cause that's where it sounds like it's coming from. I just can't get it to make the noise unless I am coasting on the bike and hitting small bumps, but it is definitely loud enough to hear over the engine...at lower rpms anyway. For all I know it could be there at higher speeds too, but motor, air, and road noise may be obscuring it. Off throttle at low speed is how I first noticed it. In or out of gear, engine off or on, makes no difference with my rattle. I just can't reproduce it when I'm not on the road.
 

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Discussion Starter · #11 ·
My rattle sounds like the same rattle KRS1 has. I suppose we could be talking about different things. For sure mine is coming from somewhere up front. I don't see how a brake pad could be making my sound which sounds like a small metal item bouncing around on plastic, like something could be inside the nose cone. I can't rule out anything coming from the instrument panel cause that's where it sounds like it's coming from. I just can't get it to make the noise unless I am coasting on the bike and hitting small bumps, but it is definitely loud enough to hear over the engine...at lower rpms anyway. For all I know it could be there at higher speeds too, but motor, air, and road noise may be obscuring it. Off throttle at low speed is how I first noticed it. In or out of gear, engine off or on, makes no difference with my rattle. I just can't reproduce it when I'm not on the road.
Do you always have the rattle or does it appear occasionally? I haven't heard my front rattle since I created this thread, but I was also not able to reproduce it.
 

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sounds like a loose screw in there from assembly..
thats one solution described by a member of
cbr250r forum..
another similar location being under front tank cover,
another lower site same loose screw lower fairing
underbelly [dropped there in assembly presumably]

if its not happening 'in or out of gear, engine off of on'
then it cant be an engine noise, which is handy..

nuisance taking instrument panel etc apart
but easy to check tank cover or under-fairing..
 

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My bike is a CB300F and the belly fairing is completely open so nothing is down there. I never thought of the plastic cover over the gas tank. That could be it too. Thanks. Mine is there every ride, but not all the time. Just when I go over rougher pavement at slow speeds.
 

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i found some info on the net and tried it, so far no noise....its gone

BUT

i want to verify this over 2-3 days before i post a link to the original person who figured it out. Because this noise comes and goes, comes and goes and comes and goes.

will reverify in a couple more days.
 

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ok id have to say that the rattling has been cured completely, its been 3 days now and ive ridden through everything trying to make it rattle again...its officially cured.

credit where credit is do, info was from this guy: CB300F Rattling Noise
 

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Thanks. I'll give it a try. The good news is, nothing that he has mentioned would be a problem down the line...just a nuisance. Until you discover for sure what is causing the rattle, you never know if it is just the beginning of some bigger issue...like detonation might have been with my first rattle.
 

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bike has gotten a bit smoother also, since the tank isnt resting on the frame any longer...fitment of the side fairings is also better as he mentioned. The black plastics arent rubbing the top tank cowl anymore either... although i dont know if this was an isolated case or if everyones plastic parts are touching each other.

the washers needed for the tank bolt is pretty big.

goodluck, i may end up keeping the bike now, was on the verge of selling it because of the rattle, but - its gone now :D
 

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Looks like you need to remove both side fairings then 2 socket near the front holding the tank cover. Then the tank cover pops up and out from the two grommets..one on each side in the middle of the cover to get to the picture showing where he added the washers...for anyone who dent have a service manual.
 

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yes you just need to undo the side fairing bolts, but dont need to remove them , they hang in place, just scoot them over.
 

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I checked out the are. Then I put the seat back on with fairings and tank cover off and rode around. I still have the sound. I don't think its coming from those mounting bolts. I do see a lot of loose rubber webbing that is probably flapping. That could be what I'm hearing. Ill try and see if I can't keep it from flapping maybe with duct tape tomorrow when I have better light.
 
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