Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Piki on September 13, 2023, 12:34:44 PM
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I open this thread to see if someone can help me, the issue is the famous "whistle" or "reverse" sound that many 400Fours have. Through a Facebook group, someone commented that the problem comes from the primary shaft pinion when its teeth wear out (it is the pinion that meshes with the clutch). That sprocket is no longer available and I had to buy it in a store in Japan, this weekend, taking advantage of the oil change, I changed the sprocket but the problem was not solved, the annoying whistle continues to sound......does anyone know where is the problem really?
Thank you in advance.
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If the pinion gear is wearing out then surely the gear on the back of the clutch would wear at the same rate? so maybe both need changing?
I can't remember ever hearing this sound BTW, so is it present when the engine is ticking over or does it only appear when the bike is rolling as knowing that should point to what it's not and maybe what it is, for instance, if you run the bike up to 30 then shut off the engine does the noise continue, (pull the clutch in to disengage or put into neutral) in which case it's on the drive/gearbox side of things, if it stops with the engine stopping that points to something either on the clutch or before the clutch.
I have heard final drive bearings make that noise when they've been overstressed with a really tight chain but not on the 400.
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Ken / Diego. What are your thoughts on this? Something in the back of my mind from 40+ years ago to do with an overtightened cam chain. Done by loosening the lock bolt and using a screwdriver down the top hole to push the rod down. Maybe take it with a pinch of salt as my memory is terrible, as you know Ken.
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Ken / Diego. What are your thoughts on this? Something in the back of my mind from 40+ years ago to do with an overtightened cam chain. Done by loosening the lock bolt and using a screwdriver down the top hole to push the rod down. Maybe take it with a pinch of salt as my memory is terrible, as you know Ken.
This happened to me as well. I would describe it as a sort of whirring sound rather than a whistle though. :-\
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That’s a good point John. Turning the engine off whilst running should point towards if it may be or not. Well remembered
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If the pinion gear is wearing out then surely the gear on the back of the clutch would wear at the same rate? so maybe both need changing?
I can't remember ever hearing this sound BTW, so is it present when the engine is ticking over or does it only appear when the bike is rolling as knowing that should point to what it's not and maybe what it is, for instance, if you run the bike up to 30 then shut off the engine does the noise continue, (pull the clutch in to disengage or put into neutral) in which case it's on the drive/gearbox side of things, if it stops with the engine stopping that points to something either on the clutch or before the clutch.
I have heard final drive bearings make that noise when they've been overstressed with a really tight chain but not on the 400.
The noise is noticeable when the engine is under load, let me explain: it is especially noticeable when you release the clutch, at which point the whistling starts, if you put the motorcycle on the center stand and shift into gear it doesn't make any noise, it only does so when the engine has a load, there are examples on YouTube.
I think you are right, the change must be for the complete assembly, both pinion and clutch basket, I want to imagine that it was just a coincidence that the person who only changed the gear was lucky enough to compensate for the wear......but it makes sense. It is changing both parts at the same time.
https://youtu.be/iXgtJOfHwiI?si=mfWATtw36hh25kK5 (example min 5:14 to min 5:30 you can check that noise)
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Ken / Diego. What are your thoughts on this? Something in the back of my mind from 40+ years ago to do with an overtightened cam chain. Done by loosening the lock bolt and using a screwdriver down the top hole to push the rod down. Maybe take it with a pinch of salt as my memory is terrible, as you know Ken.
I think that not..........I have adjust the primary and the sound continues....
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https://youtu.be/iXgtJOfHwiI?si=mfWATtw36hh25kK5 (example min 5:14 to min 5:30 you can check that noise)
It really sounds like when I over tightened my cam chain, by the same path as Deano! ;D
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https://youtu.be/iXgtJOfHwiI?si=mfWATtw36hh25kK5 (example min 5:14 to min 5:30 you can check that noise)
It really sounds like when I over tightened my cam chain, by the same path as Deano! ;D
:o :o I will look at it again but if it were the timing chain it should make a sound whenever the engine was running since it is spinning continuously......and the sound only occurs when you shift into gear or when you reduce a gear... .. In addition, the adjustment is made automatically by loosening the tensioner screw....
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[In addition, the adjustment is made automatically by loosening the tensioner screw....
Piki, that is when things are as they should be, but the 'horseshoe' is prone to seizing/stiffening and the solution short of splitting the cranks to change it, is to undo the plug at the top and give it a good tap with a screwdriver or similar.
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[In addition, the adjustment is made automatically by loosening the tensioner screw....
Piki, that is when things are as they should be, but the 'horseshoe' is prone to seizing/stiffening and the solution short of splitting the cranks to change it, is to undo the plug at the top and give it a good tap with a screwdriver or similar.
How would you know that the tensioner is working correctly? loosening the tensioner bolt and then applying tension to the top and seeing if it moves freely?
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[In addition, the adjustment is made automatically by loosening the tensioner screw....
Piki, that is when things are as they should be, but the 'horseshoe' is prone to seizing/stiffening and the solution short of splitting the cranks to change it, is to undo the plug at the top and give it a good tap with a screwdriver or similar.
How would you know that the tensioner is working correctly? loosening the tensioner bolt and then applying tension to the top and seeing if it moves freely?
If you run it with the pinch bolt undone, then a screwdriver onto end of the rod, push it very, very lightly and you should feel the tensioner oscillations as the chain is going round. If it's completely still, then that suggests its stuck and not fluctuating with chain movement.
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On my old 250 Honda if I undid the tensioner bolt & removed the end bolt a slight blip of the throttle would make the tensioner move visually in & out. Not tried it on a 400 though.
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It could well be Piki that the chain is overtight, when the engine is just spinning over it's not a huge problem but as soon as the engine starts to load up then the chain does as well, this causes it to overtighten to the point where it's stressing the others parts, the tensioner blade, the chain itself and the guide, even the horseshoe.
Not saying this is the case but it's feasible.
IF it is this you need to sort it before something snaps, if the horseshoe is stuck you may be able to get it unstuck through the sump, not enough to fix it but maybe just backing it off a little so it doesn't make the chain whine. It will need sorting at some point though, sooner rather than later.
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Big problem with all the adjusting is you keep burning your hands on the exhaust, i have put up several times a link to knocks and rattles mod kit for the tensioner bolt which whilst it does not free the horseshoe or make the plunger free is a well made stainless kit to repair the lockbolt and no i do not have anything to do with the firm
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It could well be Piki that the chain is overtight, when the engine is just spinning over it's not a huge problem but as soon as the engine starts to load up then the chain does as well, this causes it to overtighten to the point where it's stressing the others parts, the tensioner blade, the chain itself and the guide, even the horseshoe.
Not saying this is the case but it's feasible.
IF it is this you need to sort it before something snaps, if the horseshoe is stuck you may be able to get it unstuck through the sump, not enough to fix it but maybe just backing it off a little so it doesn't make the chain whine. It will need sorting at some point though, sooner rather than later.
Thanks for the advice, I will try to check if the sound comes from there, although honestly the sound comes more from the clutch area. This morning I spoke with a man who had the same whistling problem on his 400 Four, after several tests he managed to eliminate the whistling by changing the sprocket and clutch basket from the same motorcycle, that is, he changed both things at the same time and of the same engine, this agrees more with the idea of wear on the clutch sprocket/basket…..
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Big problem with all the adjusting is you keep burning your hands on the exhaust, i have put up several times a link to knocks and rattles mod kit for the tensioner bolt which whilst it does not free the horseshoe or make the plunger free is a well made stainless kit to repair the lockbolt and no i do not have anything to do with the firm
Could you show me that please?
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Look up knock n rattles mate i cant post links
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Here's the link Piki.
http://noxandrattles.co.uk/index.htm