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Discussion Starter · #1 ·
I get a noise ONLY when my bike is in the 4-5k rev range.

outside of 4000-5000 rpm the engine sounds fine, however when I hit 4k it makes an odd noise.

Also it seems to be more intense when I am getting low on fuel.

Let me try to explain the nosie:

It sounds like a piece of rubber hitting a fan,, or maybe the low rumblings of a toad or frog...

Kinda hard to describe the noise, but does anybody have any inclination to what it may be?

thanks
 

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Have you checked under the pillion seat for a frog or a toad?
There's some pretty out of it insect life in South East Asia ;)

Seriously tho, I must be one of the lucky ones as my bike doesn't make any strange noises.
Suggest aftermarket pipe to drown it out... :D
 

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I understand the pain! Mine kind of sounded like when kids put cards in their tire spokes. Taking it to the dealer on Wednesday, but from everything I heave read, they all seem like either easy fixes or just normal. Keep us updated!
 

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there's a chance is just a normal noise for that engine. How many miles do you have on the odometer? if it's not fully broken in yet, it might smooth out after a little more wear. other possibilities are a loose nut or bolt on some plastic parts that amplify vibrations across a certain range of frequencies. does it make the same noise at those rpm's in all gears? or is one gear in particularly that creates the noise at those rpms? I accidently dropped my bike in my driveway, but was able to grab the high side handlebar and at least slow down the tip and prevented any scratching, but the left side turn signal is a hair loose now, and it will give me some noise at a certain frequency, but faster or slower and it doesn't vibrate. Likely its completely normal, but definitely let us know how it goes with the dealer.
 

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The noise at 5,000 rpms is well-documented on the CBR250R forum so it's been around several years although I don't know how common it is. I don't have that rattle, but I did have the fuel cap rattle. Berk Engin has a YouTube video about the engine rattle at 5000 rpms on his CB300F and it's talked about in the comment section a little, but check out the CBR250R forum. I hope it isn't related and don't think it is, but you know Berk Engin's engine blew on his bike.
 

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Switching to an R3 may be a solution? :p

I have a CBR300r and wish I got the R3, its just a lot more expensive here in thailand, the CBR is made here and is ultra cheap.

Its not a even a comparison, the r3 is a better bike.
Just messing with you! ;)
 
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Discussion Starter · #8 ·
there's a chance is just a normal noise for that engine. How many miles do you have on the odometer? if it's not fully broken in yet, it might smooth out after a little more wear. other possibilities are a loose nut or bolt on some plastic parts that amplify vibrations across a certain range of frequencies. does it make the same noise at those rpm's in all gears? or is one gear in particularly that creates the noise at those rpms? I accidently dropped my bike in my driveway, but was able to grab the high side handlebar and at least slow down the tip and prevented any scratching, but the left side turn signal is a hair loose now, and it will give me some noise at a certain frequency, but faster or slower and it doesn't vibrate. Likely its completely normal, but definitely let us know how it goes with the dealer.
It makes the noise in any gear usually at 4k most strong
 

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One of our other members had an on-going issue with an annoying rattle then he pressed down on the fuel cap one day when riding and it stopped. Not sure what the cure is but worth a try.
 

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Here's how to check for the fuel cap rattle: https://www.youtube.com/watch?v=u7V6QzuiaUU TAP with your fingers all around the fuel cap, don't just press. If there is a spot that makes a rattle sound, you will have the fuel cap rattle. You can actually press down and rotate the cap slightly either clockwise or counterclockwise and possibly stop the rattle.
This rattle is not related to if the bike is even running or not and you could be coasting and get it since it is a vibration due to bumps on the road (at least mine was), although engine vibration could contribute. It took me 2 months of rattle before I finally figured out how to diagnose and fix the problem. A new fuel cap might work too.
 
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