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Discussion Starter #1 (Edited)
The last couple times I've ridden my bike I've noticed more noise than usual at idle, but only after it gets hot. The only thing that's changed is that I'm running ethanol free gas which only comes in a higher octane than necessary.

I've adjusted the valves which were tight on one side, fine on the other. I tried to adjust the cam chain when I had the valve cover off, the chain seemed tight and the adjuster between the cases wouldn't move (could it be really stuck?).

When I loosen the adjuster while idling, there's an obvious increase in top end noise that goes away once the nut is tightened.

This video is what it sounds like when hot

It sounds quite chainy in the video, I'm thinking either my cam chain still isn't adjusted enough or the balancer chain needs adjustment. Is it within normal noise levels? Could noise be due to bad carb synch? Is it safe to ride like this?
 

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That's a little noisy. Could be the spring in the cam chain adjuster is worn out. You can manually tighten it by following the instructions here.

That noise is unrelated to the carbs.
 

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Discussion Starter #3 (Edited)
Thank you for the link, I missed the part about turning the engine while pressing down which makes sense. I don't see any reason that part would be different for the 400 engines.

I'll try that and check the valves again while I'm at it, making sure that the dual rocker has something under one while checking the other

Update: no valve nuts/adjustments etc. have come loose, and I adjusted the chain properly thanks to the link. It sounds less chainy now when cold, I'll get it hot tomorrow and see if it was really the problem.
I tried to adjust my balancer chain and it seems like it needs the side cover to come off for a proper adjustment.

P.S really should have searched properly first but I was somewhat worried about the big scary tapping noise
 

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Discussion Starter #4 (Edited)
After adjusting the balancer chain I think the rubber must have disintegrated, it now makes even worse noise, definitely from the balancer chain part of the engine. I have vibration on deceleration now and the sound is present from idle to about 3500 then from 7000 upward
Is it safe to ride it like this or do I need to pull the engine and replace them immediately?
 

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I'm still mostly deaf, although I'm working on fixing that, so can't really identify the sound. If the consensus is the balancers knocking it's safe to ride for quite some time. I first heard mine in San Diego and rode to Redding CA by way of Baja, Key West, Caribou Me., before doing repairs.
 

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I'm still mostly deaf, although I'm working on fixing that, so can't really identify the sound. If the consensus is the balancers knocking it's safe to ride for quite some time. I first heard mine in San Diego and rode to Redding CA by way of Baja, Key West, Caribou Me., before doing repairs.
Isn't it your rebuild thread where we get to see the oil pick up almost covered by shredded rubber?
 

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Isn't it your rebuild thread where we get to see the oil pick up almost covered by shredded rubber?
Yes, you mean this picture?
201_4221.JPG
Consider though that this was 20,000 miles after I first figured out what the sound I got was. I never actually heard it, a friend did and helped me sort out where it was coming from. I was 2 weeks into a US tour and figured I'd ride it till it quit, only quit with a CDI failure that got fixed in WV and I continued on my way home.
 

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Discussion Starter #8 (Edited)
I'm still mostly deaf, although I'm working on fixing that, so can't really identify the sound. If the consensus is the balancers knocking it's safe to ride for quite some time. I first heard mine in San Diego and rode to Redding CA by way of Baja, Key West, Caribou Me., before doing repairs.
No worries at all, I probably wouldn't even have working carbs yet if it weren't for other posts of yours.

That is good to know about how long I've got for it to run. It's only at 30k kms (~19k miles) so it's frustrating and it'll bug me but at least it's not rod knock (I'm pretty sure).

That oil pickup is concerning but must have been functional still? I'd also think that the oil filter system on the 400s is much better than the earlier bikes, making it less likely to plug oil passages and wreck cams like 450s/160s/175s seem to do frequently
 

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The picture of the pickup was prior to cleaning, straight off the engine during disassembly. Yeah, partially plugged but still working fine. I rebuilt the engine due to low compression from worn out rings. These engine benefit from having the large pickup screen and a paper filter after that to catch all the small stuff. Only thing that seems to kill these is low oil level causing starvation to the left rod.
 

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Discussion Starter #11 (Edited)
HEY! only if you dumb stuff like put too much sealer on gaskets, or mis-assemble the oil filter valve... and BTW, 350s do it too :lol: and usually because of stuff like this
Oh boy those pictures are rough... Doing such things before the internet is understandable but these days the information needed to not wreck things is so accessible it's hard to excuse.
Also I don't think I've seen a cb160 cam yet that's been perfect on both sides, I'd guess it has something to do with them being the 70s version (or at least it sounds like it) of what the ninja 250 has been for the last decade or so.

I have read about the left rod issue, I've probably checked my oil every 20 km. Smart design having a plastic dipstick, even my obsessive oil checking would have a tough time stripping the threads using that
 

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Oh boy those pictures are rough... Doing such things before the internet is understandable but these days the information needed to not wreck things is so accessible it's hard to excuse.
Yeah, that was the alternator cover when I first tore down my 450... clearly a schlep worked on it previously

...even my obsessive oil checking would have a tough time stripping the threads using that
obsessive oil checking isn't bad :D
 

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Discussion Starter #13
That is certainly not a sight you hope to see in a Honda engine, hopefully that was the only cover they got into...

Hopefully it pays off someday and avoids a "ran low on oil is my engine okay because there's a hole in the case now" thread in the future
 

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That is certainly not a sight you hope to see in a Honda engine, hopefully that was the only cover they got into...

Hopefully it pays off someday and avoids a "ran low on oil is my engine okay because there's a hole in the case now" thread in the future
You mean how I got my 81 CM400 engine?

Case bottom.jpg

That hole was from the connecting rod nut on the rod trying to get out.

The PO used silicone sealant which breaks off inside and goes where it shouldn't be.
 

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Discussion Starter #15 (Edited)
Haha yep pretty much, I guess it's not surprising that improperly maintaining and engine leads to catastrophic failure. After all an engine is just 20+ explosions per second transformed into rotation and heat.

Update on the issue: It's been 25 kms with this noise and it doesn't seem to be getting worse, just consistently rattly and annoying noise from the balancer chain area. I guess I'm finding out what the bottom end of a cb400t looks like this winter. If I purchase a 450 balancer set, can I still follow the 400 manual for installation? Also is there any reason the top end would need to come off to split the cases?
 

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The 450 balancers are installed exactly the same as the 400's, same marks apply.
Remove the engine, stator, clutch and shift rod, turn upside down and remove the lower case. Nothing on top needs to be disassembled
 

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Not sure if shipping to Canada is economical, but I've got a set of 450 balancers on the shelf.
 

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Discussion Starter #19
Perfect! Thanks for the threads and info, I'm sure I'll be able to get it done using a combination of the threads posted. Just have to wait for a rainy week or so now.
 

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Discussion Starter #20
Not sure if shipping to Canada is economical, but I've got a set of 450 balancers on the shelf.
I actually have a US shipping address in Washington, I was going to buy a set off of ebay but if you've got a pair I'd be interested in them!
 
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