Cam Chain Adjustment


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cross
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Re: Cam Chain Adjustment

Post by cross »

herdygerdy wrote:
Sat Sep 10, 2016 5:08 am
Pleased you found it useful Sparky. Great to learn and do stuff on these trusty old gals yourself.

And don't forget to put the oil pool plates back in on the Inlet side if you were doing the shims.

Now get out there and ride it like you stole it.

Cheers...Tony
I have a question on the front adjuster.
I've recently done valve adjustment and have also adjusted cam chains and this is my 3rd time so i get the procedure. Now, this time when i did, i left things sit for a while until i got to cleaning the valve cover gasket for reassembly. Before i closed things up, i rechecked cam chain tightness and front one was loose, with lots of slack. I re adjusted it again and here is my question, the adjusters bolt is all the way up to the lock nut and i feel that the chain still his very slight slack. Does this mean that the chain reached it's life?
I'm also still think as to why did it loosen up after sitting, i'm positive that i rechecked it several times. Now that it is closed up, i'm thinking or removing the valve cover again to recheck it again since the engine is still tilted

Thank you
Sasha
Sasha

'82 Honda CBX
'99 Triumph TBS
'01 Honda Valkyrie

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EMS
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Re: Cam Chain Adjustment

Post by EMS »

The screw does not adjust the slack. The screw pinches the slider rod and keeps the adjuster spring from tightening. You need to loosen the screw and let the spring pull the adjuster so it pushes the guide against the chain. You need to make yourself familiar with how the adjuster works in order to make sure you are doing the right thing.

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Re: Cam Chain Adjustment

Post by herdygerdy »

Hi Sasha,

If you were still seeing slack in the chain before putting the cam cover on, I'd definitely be pulling it again before tilting the engine back up.

Not quite sure exactly which of the two cam chains you are referring to when you say '...and the front one was loose, with lots of slack.' and am struggling to think how cam chain tension could change just by sitting if set correctly with this procedure.

When you say 'front', are you referring to the long run of cam chain at the front of the motor that goes down to the crankshaft?

So let's clarify terms so we are on the same page. (and apologies if you know all this stuff already, but this may make it clearer)

The long cam chain coming from the crankshaft all the way up to the exhaust camshaft is the 'A' chain. Adjustment on this chain is ONLY done by loosening off the 10mm chrome dome nut located on the BACK of the cylinders/barrels below the float bowls of carbs 3 & 4. You can see the round top of the tensioner for this cam chain just below and slightly forward of the inlet camshaft (more on that later).

The short cam chain at the top of the motor running between the exhaust and inlet camshafts is the 'B' chain. Adjustment of this chain is ONLY done by loosening off the lock nut and pinch bolt on the FRONT of the cylinder head.

So when you refer to 'the front one', which chain are you referring to? A or B?

If you are referring to the 'A' chain, then twiddling about with the lock nut and the pinch bolt at the front of the cylinder head (ie; the adjustment for the B chain) will have no effect at all (because it has absolutely nothing to do with the A chain). You will need to adjust this A chain by undoing the 10mm dome nut on the back of the cylinders/barrels.

NOTE: There is a long solid slipper blade located in front of the front run of the A cam chain and there is always a gap between it and the front surface of the chain. (Its a design flaw IMHO, but that's a whole other story). Is it possible it is that gap between the slipper blade and the A cam chain that you are referring to? If so, that is normal and there is nothing wrong.

Now when you gently rotate the crankshaft backwards and forward a few degrees, you should see slack in the A chain transferring between the front and back runs of the A cam chain. While holding the slack on BACK run of the A chain (by putting slight forward (clockwise) rotational pressure on crankshaft with your 17mm spanner), undo the dome nut and the A cam chain tensioner SHOULD spring out to take up the slack.

If this isn't happening, is quite possible your A cam chain tensioner is gummed up / stuck and is no longer able to automatically 'spring' outwards (ie; towards the front of the motor) to take up the slack when the dome nut is undone. I have seen this occur on quite a few engines.

The A cam chain tensioner at the back of the engine can usually be 'un-stuck' by first loosening off the dome nut. Then, while holding that forward rotational pressure on the crank (to put all the A chain slack to the rear), push down VERY firmly on the TOP of the A cam chain tensioner (it is the large round black part just below and slightly in front of the inlet camshaft. You may need to push firmly down on top of the tensioner (in direction of the red arrow in the image below) as you tighten the dome nut to hold the tensioner firmly against the back run of the cam chain. This cutaway image clearly shows the relationship between the A cam chain and its tensioner.
CBX A Cam Chain 3.JPG
If you look carefully at this image you will see the long tensioner spring inside a black rubber tube. This spring pulls the two parts of the tensioner together so as to make the flexible blade on the front of the tensioner 'bow' outwards towards back surface of the A cam chain to take up the slack. Also, in this image, you can see we've temporarily replaced the 10mm dome nut on the back of the cylinders/barrels with a normal 10mm nut.

Now the B cam chain tensioner can also become stuck. Back off the lock nut and pinch bolt. Then, while still keeping that forward rotational pressure on the crank (to put all the slack on the bottom run of the B cam chain), push down hard on the BOTTOM run of the B chain that runs between the inlet and exhaust camshaft. Push it down firmly as far as it will go and release. Do this vigorously a few times and you will observe the shaft on the front of the B cam chain tensioner sliding in and out of the hole just inside the front of the cylinder head.

Keeping that forward pressure on the crank, remove your hand from the chain to let it 'relax' fully. This will then allow the B tensioner to 'do its thing' and bow upwards to take all up the slack in the bottom run of B cam chain. Then do up the pinch bolt (just nipped up firmly remember, it's only a pinch bolt that just pushes up and locks against the underside of the B cam chain tensioner shaft) and then do up the lock nut, again only nipped up.

You should then be good to go Sasha. Let us know how you get on.

Cheers...Tony
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Re: Cam Chain Adjustment

Post by cross »

I was referring to front cam chain adjuster on the front of the engine. Rear or A cam chain was adjusted per your instructions and is nice and tight.
B chain has some slack and I loosened the lock nut and the bolt, applied forward pressure on the crank, watched slack move from top to bottom of the chain, screwed the bolt in until it was nipped but that happened once it touched the locking nut. I nipped the nut too. I rotated engine sever revolutions and did forward and backward pressure on the crank and there is still slight slack while applying forward motion, I tightened the bolt a bit more and it got tighter. I mean, it’s probable at 95%+ but not as tight as A chain. I’m worried about this bolt being so far up against the lock nut, I don’t think that there will be any more adjustment possible in the future. Perhaps I did something wrong but ill definitely pull the cover off and recheck.
Any additional input appreciated

Thank you
Sasha
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Sasha

'82 Honda CBX
'99 Triumph TBS
'01 Honda Valkyrie

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herdygerdy
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Re: Cam Chain Adjustment

Post by herdygerdy »

Hi Sasha,
OK, I understand now and it seems like you've got it. Your lock nut looks pretty 'tall' (deep?) especially when combined with the thickness of the flange on the bottom (top?) of the nut snugged against the cylinder head and the height of the hex part of the nut itself - at least that's what it looks like compared to the OEM ones on twin shocks that I am more familiar with, which IIRC are much thinner.

As you suggest, the excess height of the head of the pinch bolt may be pushing hard up against the underside of the lock nut, and therefore may be preventing the pinch bolt from fully securing the front shaft of the B cam chain tensioner.

The pinch bolt is a standard 8mm thread so if you have a spare (shorter/thinner) nut in your stash of spares, compare it to what is fitted and try that.

Looking carefully at your latest pic, it looks like there may be an O ring trapped between the underside of the bolt head and the top of the nut, which could be complicating the issue. I'd undo the lock nut and remove the pinch bolt entirely so you can see exactly what is going on, make sure everything is squeaky clean and all O rings etc are where they need to be.

Also, if you happen to have a spare round black sealing plug that goes into the front of the cylinder head (or you are able to carefully extract the one already in the head without damaging it and re-use), you can remove it. Then, while holding all the B chain slack at the bottom of the run, simultaneously slide a screwdriver or similar up the now exposed hole (from which the sealing plug was removed) to push firmly on the end of the tensioner shaft. This will force the flexible blade in the B tensioner to bow upwards to take up all the remaining slack in the B chain.

You could even give that a go before you go to the trouble of disturbing the cam cover again.

Hope this helps...Tony

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Re: Cam Chain Adjustment

Post by cross »

Tony, I’ll try that. Thank you very much for your help.
One other question, I remember unscrewing the bolt with my fingers until it became hard to turn. I would probably need a wrench to get it out all the way, is this normal?

Thanks
Sasha

'82 Honda CBX
'99 Triumph TBS
'01 Honda Valkyrie

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Re: Cam Chain Adjustment

Post by herdygerdy »

That would be because (IIRC) there is a groove half-way up the thread of the pinch bolt for a small O ring. Sometimes those tiny O rings get munged up or caught in the thread in the cylinder head during removal which prevents it from being readily removed by hand. Proceed with your wrench and you'll see what I mean.

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Re: Cam Chain Adjustment

Post by steve murdoch icoa #5322 »

Following along with this.
Thanks to both of you for the detailed explanations and pic.

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Re: Cam Chain Adjustment

Post by daves79x »

No, the only o-ring on the '80-'82 cam tensioner bolt is one that sits in a recess in the lock nut. The '79 is the only one that has the o-ring in the tensioner bolt groove.

You need to completely remove the assembly (bolt and nut). Check for pulled threads in the head. I suspect you are starting to pull some aluminum and that is gumming up the threads. Be very careful, or a Heli-coil is in your future.

With the cam cover off, use a blunt drift to push down of the bottom run of the horizontal tensioner, with the adjuster bolt loose or removed. The bottom run and attached tensioner rod should move freely. Once this is confirmed. clean everything and re-install the tensioner bolt and nut, with a new o-ring. Be very careful with tightening both the bolt and lock nut. Tightening either one too much will pull the bolt right out of the threads in the head.

Dave

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Re: Cam Chain Adjustment

Post by cross »

I'll definitely have to recheck everything as suggested. I hope threads are good :(


Thank you all
Sasha
Sasha

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'99 Triumph TBS
'01 Honda Valkyrie

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Re: Cam Chain Adjustment

Post by herdygerdy »

Thank you for the clarification on the 80-82 set up Dave (every day's a school day!) and fingers crossed for you Sasha that the threads are still good.

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Re: Cam Chain Adjustment

Post by cross »

Thank you sir
Sasha

'82 Honda CBX
'99 Triumph TBS
'01 Honda Valkyrie

:auto-sportbike:

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Re: Cam Chain Adjustment

Post by cross »

daves79x wrote:
Wed May 05, 2021 8:44 am
No, the only o-ring on the '80-'82 cam tensioner bolt is one that sits in a recess in the lock nut. The '79 is the only one that has the o-ring in the tensioner bolt groove.

You need to completely remove the assembly (bolt and nut). Check for pulled threads in the head. I suspect you are starting to pull some aluminum and that is gumming up the threads. Be very careful, or a Heli-coil is in your future.

With the cam cover off, use a blunt drift to push down of the bottom run of the horizontal tensioner, with the adjuster bolt loose or removed. The bottom run and attached tensioner rod should move freely. Once this is confirmed. clean everything and re-install the tensioner bolt and nut, with a new o-ring. Be very careful with tightening both the bolt and lock nut. Tightening either one too much will pull the bolt right out of the threads in the head.

Dave
Hi Dave,

Does the nut and bolt on my picture look stock?


Thanks
Sasha
Sasha

'82 Honda CBX
'99 Triumph TBS
'01 Honda Valkyrie

:auto-sportbike:

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Re: Cam Chain Adjustment

Post by daves79x »

Yes, for sure.

Dave

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Re: Cam Chain Adjustment

Post by EMS »

The nut changed from a plain 8mm hex nut to a 10mm flange nut for the 1980 model

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