Honda-SOHC
SOHC.co.uk Forums => CB650 => Topic started by: Veedunk on September 06, 2021, 10:05:36 AM
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Hi, I’ve taken my cylinder head off due to trying to find an oil leak…I’m about to replace the gaskets/seals and hope that fixes the problem but before it all goes back I wanted some advice about these chain marks? Is that normal wear to the inside of the head and the barrel casing?
Many thanks
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No either the tensioner isnt workinh and/or the cam chain is worn out
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Looks like a good candidate for a strip complete strip down.
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erm, good job you took it apart.
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Yup its a full strip, there is no link on those hyvo chains, i know they must have been assembled in the first place but those pins always look twisted at the ends to me
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Yup its a full strip, there is no link on those hyvo chains, i know they must have been assembled in the first place but those pins always look twisted at the ends to me
The cam chain isn't a Hyvo Bryan but the primary chain is 😊😊😊
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Im sure the 650 has a small hyvo camchain lick the 250N
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Im sure the 650 has a small hyvo camchain lick the 250N
Indeed you are probably 100% correct and I apologise. I didn't see that it was a 650 and I've never seen a complete 650 in person ever, let alone the innards of the 650 engine 😊😊😊😊
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No need for appologies Julie, the day we stop learning is the day we give up! Just for info the 650 is a stroked 550 not a bored one
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Thanks for all the replies, not the answer I was hoping for though!
Before I go ahead and strip it down, do you think these could be old wear marks? I’m only asking because I bought this bike a year ago after a full rebuild during lockdown by the previous owner, it’s probably done less than 1000 miles since then.
I will drain the oil today and see what sort of condition it is in.
Thanks again
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Drop the sump and also inspect the oil pump and filter.
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Rebuilt? By who and how and what was replaced plus was it set up.correctly afterwards, especially the cam chain adjustment. Those marks look new and shiny so i would say were recent and done by this chain and to my mind that compromises the chain. Sorry
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As a minimum I’d drop the sump and inspect the primary chain, filter and oil pump.
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Ok I’ve dropped the sump, removed the oil filter and removed the oil pump…
There are very, very fine metal particles in the oil filter and the oil from it, same with the oil pump, if I didn’t know better I probably wouldn’t have noticed them. However when I drained the oil from the sump there were some bigger particles which I’ve tried to show an example with the photo, but certainly not much considering the amount of wear.
I don’t know what to look for on the primary chain if I’m honest, it looks normal to me.
As for what was rebuilt by the last owner, I don’t really know, but I will try and find out.
The bike has always run well but not been as quick as I would have expected but I don’t have anything to compare it with as I’ve always had modern bikes. Would this sort of wear prevent the bike from revving fully as its always sounded like it’s screaming at about 6000rpm?
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There's something very and distinctly unusual about that chain and wear in first picture, maybe give us a clear picture of the chain stretched out and a picture of the cam sprocket to help opinion of what's really going on there.
A "Hyvo" type if ever fitted doesn't ordinarily have a centre set of link plates running along the chain (unless that first picture has two runs next to each other as it lays there) it certainly looks wrong from that picture.
Generally a Hyvo will have sprockets looking like small gear teeth rather than the curved bottom form of conventional link chain hardware.
Unusual to touch the sides of castings to to anything of that degree illustrated.
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As you can probably guess this is all new to me, really appreciate people taking time to help me out.
I’ve taken some photos of the chain as requested.
Many thanks
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Looks like it has either the wrong cam chain fitted (too wide) or the camshaft sprocket is wrong (too narrow).
BTW the camshaft also looks fairly worn to me.
Do we have a CB650 expert on this forum?
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I’d definitely split that motor in order to clear all debris from oil ways/galleries.
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"Do we have a CB650 expert on this forum?"
Ok, to the OP, the 650 is very closely related (development of 550) with not much change, but obviously some significant ones that familiarity of the forum may not initially cover. It may take some time to build you a picture fully to understand what you've got there.
https://www.facebook.com/102952896441309/posts/the-cb650-engine-disassembled-i-just-cant-help-but-feeling-joy-seeing-this-much-/2453570004712908/ looking at the photos in link, it does seem as Bryan believes that it's a Hyvo type camchain (the only one of these engines equipped with? ) but, and it's a big BUT, the chain link form in that link is definitely different with no apparent centre line that would interact with the sprocket in a different way, like control of centering from tooth form.
Additionally, the cases in that link appear to show a top face (site of wear on yours) of a different and square form to accommodate a wider chain as original.
Wondering whether this example here has had 650 components built into a 550 pair of crankcase (without clearance for Hyvo, wider chain) and given this odd interface.
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Ok I’ve had a look at the oil strainer and there’s a small amount of metal deposits but certainly not much.
I tend to agree that the casting shape on my bike is different to the link, I will add a photo to try and show it more clearly and the wear/damage to that area. And yes my chain is narrower to the one in the link so there’s definitely something wrong here….
As for the pistons, they are all the same size and have all the rings so probably just a trick of the light there!
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I have only ever done one 650 and memory tells me the chain looked like the one in the pic with the outer side lates holding the chain onto the gears.
Similarly i have only ever seen that type of wear in cylinders once and that was on a 750 serviced by the owner who did not understand how the camchain tensioner worked and thought he followed the procedure in a spurious manual but didnt and the camchain managed to eat a hole in the block oil leaked out of
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that hyvo chain does not look a good fit on the sprocket. With the chain sitting on a tooth....how much of a side to side gap is there? Hard to tell by eye.... but I wonder if the chain just wasn;t the right part and sort of fitted.
Must have made a fair bit of noise when it was started up like that, until it wore a channel in the tunnel. I've seen worn tensioners and guides, and fore/aft slop leading to rattly cam chains, but never had one that chewed its way sideways.
I'd be replacing the chain and tensioner, after cleaning out the bottom end to get rid of the swarf.
I also think that cam looks worn ....
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Thanks again for everyone’s input here, it really is much appreciated but a little overwhelming at the same time!
I’ve put the chain on the sprocket, I would say there is about 1.5mm give or take of movement side to side…it doesn’t feel like a tight fit and quite loose on the sprocket teeth. Also, I’ve checked the David Silver website and they list a cam chain which looks different to mine, more like the one in the link posted by K2-K6, so I’m pretty sure it’s got the wrong chain fitted.
Very occasionally and only when starting from cold would I get any rattling from the engine, more like a single slap and then the noise would stop straight away and I never gave it any more thought as the engine ran fine.
As for the cam being worn, is there any way to check? It does feel slightly uneven over the lobe with a slight ridge on one side.
Cheers
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That cam is definitely worn, you can see it. 2 choices, find a good used replacement cam or send it to Newman Cams for building up and re profiling. The 1st option will by far be the cheapest option.
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I’ve tried a few suppliers today but not had any luck finding a camshaft either new or secondhand. They are obviously quite a rare item.
It looks like I will get it re-built unless anyone has a spare camshaft lying around in the shed??
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The underside of the chain is different to the top..which allows it to mean
with the sprocket.
This is my chain, from an 81 model so it may be announced as it looks different.....If only I could post a piccie..
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..meant to say, may be an upgrade. This is my can sprocket.
[attach=1]
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..is the chain running in the wrong but of the cam- chain tunnel. It looks as if it ought to run in the square bit, but may have been routed in the narrower central bit and so came into contact with the head at either side.
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My new parts from David Silver just arrived this morning so I’ve taken a couple of photos…
The chain on the left is the one still in the bike, the chain on the right is the new one.
The sprocket on the left is the old one, new one on the right.
Some obvious differences…not sure if this will be the cause of the problem but somethings not right!
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I’ve just noticed the photos above have rotated by themselves but you get the idea.
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My chain is like the one on the right, your new one.
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Chain in bike is not original