| |
The
Cam Chain Tensioner (CCT) |
|
|
|
| Do Blackbirds ever have cam chain problems? Quote ".My bike is making a knocking sound when warming up and I was told to have the cam-chain checked..Is this a possible cause?"YES - Blackbirds can suffer with cam chain tensioner (CCT) problems. However not all Blackbirds suffer as much as others. Another valid point is that the problem is actually only the CCT, not the cam-chain itself! CCT failure sounds like a rattle at about 3000rpm, and does sound worse at a cold tick-over. It somehow never seems as bad when the engine is warm! |
|
| So what is a Cam Chain Tesioner (CCT) and what does it do? The cam chain is a chain that connects the crankshaft to the camshafts (the Honda Blackbird engine is DOHC - Double Over Head Cam). This chain not only connects the crank to the cams but it also maintains the correct valve timing. Valve timing is critical, to maximise engine performance as well as preventing severe engine damage. The cam chain requires a certain amount of tension to ensure that the chain does not jump a tooth. This is where the Cam Chain tensioner comes in - it applies a certain amount of tension on the cam chain at all times to maintain correct camshaft & valve timing. The Honda Blackbird has an automatic style cam chain tensioner that does not require periodic adjustment since the tension is adjusted by a spring within the CCT. |
|
 |
Although
this is not a Honda Blackbird engine, this illustration
helps enormously. Here we can see the cam chain encircling both the top and the bottom of the engine. The camchain mates the big end, (the crank shaft) or the lower part of the engine, operating the up and down movement of the pistons, to the top end - where the camshafts operate the opening and closing of the valves. The timing of the two elements is critical!The camchain guide, is in contact with the cam chain.The camchain tensioner applies pressure to the cam chain guide, ensuring smooth operation of the said cam chain.Therefore if inadequate pressure is applied to the cam chain guide, then at approx. 3,000 rpm the chain will make a distinct rattling noise - (often, as described above is heard better when the bike is running from cold). |
| Where is the cam-chain tensioner on the Honda Blackbird? | |
 (The silver coloured object) |
|
| What's in it? | |
| There
seems to be a lot of mystery surrounding the cam chain tensioner (CCT) for
the blackbird and additionally a lot of rubbish spouted about how it works. It would appear that many CCT’s are changed both under guarantee and by the user without any real reason and that often, there is no reduction in vibration/noise after the CCT is changed. All
the CCT does is exert a thrust on the cam chain guide to keep the tension
within the cam chain correct. The design of the tensioner prevents the
cam chain forcing the tensioner back when the engine is revved. There
are no ratchets inside and you can see if the spring within the tensioner
is broken or not with the CCT on the bike. It is assumed that there is
a vibration or noise that makes the user suspect the CCT has failed which
can be used to see if the CCT is the cause of the problem. |
|
| Disassembly:
So what’s
inside the CCT and what is likely to fail? The simple answers to these two questions are not much and a spring. 1/ The whole assembly is held together with a single circlip that can be removed by prising off with the terminal driver. |
|
Prising off the retaining circlip |
|
 |
|
| 2/ As the spring within the tensioner is pre-tensioned before the circlip comes right off, we hold the plunger in to stop the whole lot springing apart. | |
Keeping
the plunger depressed |
|
 |
|
| 3/ With the circlip is fully removed, using the screwdriver to stop the adjuster screw from turning. Slowly letting the spring unwind until the plunger assembly comes free from the front of the tensioner body. At this point the spring will probably unwind totally very rapidly | |
| 4/ The CCT can now be totally disassembled. There is likely to be congealed oil in the back of the body | |
 The CCT’s internals |
|
As you can see there is not much inside the CCT, spring tension causes the helix to turn which pushes the plunger forward onto the camchain guide. |
|
| So now we know a bit more about the cam-chain tensioner, not so scary, but if you suspect, that rattling at 3,000 rpm particularly when cold, is you need a new camchain tensioner, what are the options? | |
| Replacement Cam Chain Tensioner or Manual Cam Chain Tensioner? | |
| Replacement cam chain tensioners are easy to pick up. Any Honda Dealer, David Silvers, Jaws Motorcycles etc | |
| Or what about a manual cam chain tensioner? | |
Well I can vouch for them, I had one fitted at approximately 20,000 mile
and saw me through to 50,000 on my Honda Blackbird, with one minor adjustment,
which was just simply the spanner inserted on the end and a quick tweak.
Although I've parted with the xx now, I'm sure it'll serve the new owner
for many years to come (no fairings off, nothing). Do a google search
on Manual Cam Chain Tensioners |
|
 |
|
We hope you've found this page both informative and useful. We always welcome feedback from xx owners regarding their experiences, so please don't hesitate to contact us if you think there is something missing from this page |
|
