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Featured Honda CB400 gear change clunk

Discussion in 'Naked' at netrider.net.au started by evman, Apr 29, 2015.

  1. This is the first bike I have owned, so I'm not sure what is normal, but whenever I change up gears on my 2009 CB400, there is a very loud clunk, before I let the clutch out. Is this normal? It happens in all gears. Being gentle doesn't seem to help.

    It seems to only start once the engine is warmed up. I changed the oil with Motul as soon as I bought it. The clutch lever seems to be adjusted properly. The bike has 16000km's

    Any ideas?



    Thanks
     
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  2. I would say its definitely not normal. Mine doesn't make a sound changing gears that I can really hear, except as its notches into 1st.

    How much oil did you put in it when you refilled it?

    Can you sight the oil in the sight glass with the bike standing perfectly upright?
     
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  3. Yep, the oil level is at the top of the glass when level.
     
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  4. Maybe you need to let someone more experienced or familiar with bikes to take it round the block, and get their opinion. I know nothing about the gearbox, don't live in Sydney, so I'm done.
     
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  5. Is it when the gear engages? or after it engages?

    If you change gear too gently, there is more time for the (layman terms) "gear bits" to increase their differential speed, so more of an abrupt change with the dogs engage.

    you could try engaging gear faster but... first I'd be checking the chain tension. too much chain slack will exacerbate any clunk from gear changes

    happy to pop over and have a look, just not this weekend..
     
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  6. It's when the gear engages, i.e when shifting the gear lever up, before letting out the clutch. I checked the chain when I first got it, and it was fine, but I might double check it again. If I can't figure it out, it would be great if you could look at it.

    I'm wondering why the heat affects it as it's perfectly fine when I first drive down the street in the morning? I've got Motul 10w-40 fully synthetic in it as recommended by the local Honda dealer. (I can't compare to before the oil change as I was more worried about traffic etc than the bike for the few days I rode it with the old oil!)

    Another thing I forgot to mention is when I put it into first from neutral (with clutch lever in), there is a slight jump forward of the bike. Subtle, but definitely there and repeatable. Although the clutch doesn't engage until released a fair way.
     
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  7. That's completely normal.
     
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  8. that jump into first is normal.. is due to the inertia of the gears all suddenly stopping.
    just have brake on when changing into 1st from neutral, all good.

    when I change into 1st after startup, there is a much bigger jump, as not enough oil between the clutch plates.. that clunk is overcoming stiction.
     
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  9. As oldcorollas mentioned, might be to do with the way you're shifting (he used fancy words like differential that I'm not going to attempt to repeat). If you let your thingy speed slow down too much your other spinny bit might be going slower than .. fcuk I need to learn words. Anyway check out this video someone showed me when I asked about gear changes. He specifically mentions the clunk and explains it:


    .. or you might be fine at gear changes and have some problem with your bike.
     
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  10. I'm definitely doing it the wrong way looking at the video. I'll try preloading the gears and flicking the throttle off today and see if that solves.

    Thanks
     
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  11. evman, like you, I went to Motul 5100 based on recommendations (less friction, more power, quicker changes) and had exactly the same heavy clunk going up through the gears.

    The first and least costly option is to swap out the oil and try the relatively cheap Honda-branded 10W-40. It's mineral-based and heavier but I've found gear changes to be smooth with just a slight snick. Also, before doing that, you might just try sharpening your gear changes by not pulling the cluth right in, just pinch it in a centimetre or so and smash through those gears - no time to clunk :happy:
     
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  12. I tried preloading today, and it seemed to solve it. I found downshifting preloaded a bit odd as it would often just go down a gear on it's own with no clutch, even with fairly light force, although it was smooth. Next oil change I'll try a cheaper (read normal) oil and see how it affects it. I do think it's harsher than it should be when I don't preload (it's quite a solid thud).

    thanks
     
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  13. Evman, have you had any success with your gearing trouble?
    Has your issue of clunky gears disappeared?
    Did a different oil make any change?
    Did practising and fine tuning your gear changes help?

    I am currently attempting to relearn how to change gears as I am currently suffering from the same issue you mentioned at the start of the thread. My gear changes are quiet and nice until the bike becomes warm and then suddenly becomes clunky and loud.

    I am riding a 2010 CB400 with 40,000kms on the clock.

    I recently changed the oil to a semi synthetic 10w40 blend and played with the clutch cable. I have not been able to solve my dilemma, so as I stated before I am working on my gear changes.

    Thanks in advance.
     
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  14. I haven't changed my oil back, as I figured I'll just wait until the next change is due. I have improved it though, especially upshifting, by putting pressure on the gear leaver before changing gears and not fully depressing the clutch, however it's still clucky going down the gears, especially the lower ones. But being smooth with it makes a big difference. The fact that its get worse when warm suggests to me the oil is too thin, so I will try a cheaper, thicker oil next time.
     
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  15. If you're using 10w40 try 15/50 or 10/50, cheap oil with our summer sounds like a bad idea. Have you tried clutchless up-shifting at all?
     
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  16. Yeah, when I mean cheaper oil I mean anything other than Motul, I think it's more suited to modern engines, which the cb ain't. I do semiclutchless in that I only pull the clutch in a little, and it's fine.the main thing is preloading the gear leaver.
     
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  17. Hey i recently gpt a cb400 aswell and it does the sane clunk just befpre i release the clutch.....did you find out what it was?
     
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  18. it was my technique. I think these bikes are just a bit clunky if not preloaded.
     
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  19. I am worried because i get the clunk just after i release the clutch out in 1st and second gear....how did ur sou d go away what technique do u use now
     
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  20. You need to put a bit a pressure in the gear shifter before you pull in the clutch, then only pull in the clutch a little way and should slip in to 2nd smoothly. You just need be smooth and gentle about it all.
     
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