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Engine Noise CBF250


Guest nathanjoe
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Honda CBF250. 29000 miles.For a while now there has been a knocking noise from the bottom of the engine that get louder around 3000rpm. I've checked the clutch, timing chain and oil pump they all seem fine (as far as I can tell). The noise has been there for a good few thousand miles and the engines never skipped a beat, although it has recently got louder. I'm out of ideas, help!


below is a video of the engine noise, you'll hear the noise get louder when i rev the bike.


https://www.youtube.com/watch?v=SAaLevb ... e=youtu.be

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Its always had the right amount of oil in while I've had it but for previous owners who knows. Seems like just getting to the bearing would be beyond my mechanical skills (judging from the manual I'd have to take the engine out and split in in half). How serious is it? I mean am i just lucking out every time it makes it back home or is it something that can wait?

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Something is definitely loose...


But usually big end bearing knocks are more regular and consistent with the engine than that from the ones I've heard. Still could easily be the problem.


I've known Hondas have clutches that go awry and make death rattles. But it sounds like the crank from that video.

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any suggestion on way of checking that it is the bearing? can it be done without taking the engine out? through a crank cover or somin? its not very clean in the diagrams I've got of the engine whether you can see the main bearing by taking the crank covers off.

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you can drop off the left handfront engine casing but check if it contains oil before removing and see how much movment there is in the crankshaft if you can feel any up and down movement then its fooked,big ends are not so easy to check unless you strip the motor down to check them

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  • 3 weeks later...

Nah mate it's none of the above, I have the same bike and sorted the very same problem out.

It's the camchain tensioner gone weak and you can confirm this by taking out the screw (cover) from the tensioner, stick a small screwdriver in the concealed slot in the tensioner, start your engine and then turn this screw anti clockwise. You will hear the engine sounding as it should, problem is you will have to do a modification to the tensioner as I and a friend have done.

Look no further than this, http://www.bikesandtravels.com/biker.aspx?ride=714

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