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Sixth Gen VTEC Cam Chain Tensioner theory of failure.


srqjohnson

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I have a 2003 VFR which has begun the unmistakable Cam Chain Tensioner rattle.

It is right about on schedule, as the odo is showing around 40K.

 

I am fairly certain it is the front one and have bought a Honda replacement and am preparing to replace it.  I have read most of the very good info here and a few other places concerning this endeavor.

 

I am simply uncertain how replacing a part as simple as the tensioner can cure the problem, though the general consensus is that it surely does.   As we all understand, there is a long foot, if you will, which pivots at one end and rides against the outside of the cam chain. Pressure is applied against this foot by the tensioner plunger to remove working fluctuations in chain tension and, additionally, to continuously adjust the foot position to compensate for wear.

 

Looking at the tensioner, it appears to be a spring loaded screw assembly acting as a rotary ratchet, rotating the tensioner out as wear progresses over time. This is a one-way operation, IE: the spring loaded screw will find it easy to rotate the plunger out, but there will never be enough pressure to cause the screw to rotate against the spring.

 

In conjunction with this, there is engine oil supplied under pressure which tends to force the tensioner plunger out against the foot, and it is held out at it's position by the spring/screw/ratchet assembly, compensating for wear over time.

 

OK so far so good. So how does the tensioner fail? And more importantly, how does replacing it cure the problem? There are a few possible failure modes: The spring can break, or fatigue over time and stop acting as a ratchet, I assume. But reading up on the issue never mentions broken springs.

 

The plunger could reach the end of it's travel, and as the replacement is identical, replacement would not cure the problem.

 

Or, the plunger could wear enough so that there is too much oil leakage around it and it is no longer acting as an almost ideal piston and is not able to exert as much pressure on the foot as designed, hence opening the oil hole a trifle, as is popular for various reasons, would probably cure it, without replacing the tensioner at all. This could explain the mysteriously small hole in the gasket for oil to begin with.

 

Incidentally, there is much written about disassembling the tensioner and adding more 'wind' to the spring, leading me to believe the oil situation above makes the most sense.

 

I would sure like to hear from some others on this subject, as I probably do not have it figured out.

 

Thanks in advance

Kirby Johnson

Sarasota, Flaaaaaa.

 

 

 

 

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After reading everything I could find, I replaced my front last year with a new Honda unit. Within 2.5k miles, it (or the rear) started rattling slightly on occasion when hot. I'm thinking that I will take the old one and try the rewinding method. I'm at 24k miles.

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I have not replaced mine yet...And after thinking this over a bit more, I believe I/we  might be able to learn something in the process.  You have to take that little key and retract the plunger by 'winding up' the spring and screwing back down the plunger, as part of the removal process.

 

No where I have read, has anyone bothered to count the turns to fully retract the plunger.  IE: is the plunger at full extension or not?  It is my understanding that there are 'X' turns built into the design.  I will count the turns on the new one also. So I believe I have enough discipline to actually sit there and count and record the turns to retract it before I plunge headlong into removing and replacing this thing.  That is what I will try to do.

 

I will report back when I have this done and we will see if anything is learned.

 

 

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This video may be of interest.

 

https://www.youtube.com/watch?v=XG6c_uhrVOw

 

I'm not sure what to make of this.  Unless I interpret incorrectly (a distinct possibility), it appears that tensioner failure is more "unwinding of the spring" vs actual parts wear or breakage.  All he seems to be doing is to rewind / reset the spring to account for wear.  I'd love to know if that's correct and if what he's doing just gets the tensioner back to where it's working again as intended.  That would beat spending the cash for new ones presuming the procedure works. 

 

CCT's seem to be like stators - some engines go quite a good ways with no issues, while others need service at a shorter interval.  My CCT's are nearing 30,000 miles and no issues (knock wood).

 

 

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Cogswell, thanks.  Yeah I saw that video before I posted above.  My theory is that his rewinding the spring to get a bit more 'torque' if you will, on the screw may compensate a tiny bit for loss of oil pressure through that tiny hole in the gasket.

 

I have wound and unwound the new one I bought from Honda, and the spring is fairly weak.  IE: just enough to rotate the screw inside the plunger to take out slack, but not enough to do any chain tensioning.  For instance, the factory supplied key used to wind the spring is made of very thin sheet metal.  According to Honda's drawing supplied for you to make your own key it should be 1mm thick.  I just mik'ed the factory one and it is 0.8mm.  So you can see the spring is pretty flimsy.   

NOTE:  As part of the process, you have to unwind your new one, and use the supplied key to wind (retract) the one on the engine to remove it if you do not have two keys.  I fabricated a spare key from Honda's drawing and had to test it on my new CCT.

 

My theory is that there is a very restricted oil supply to push the plunger out, as there is not any real oil FLOW through the tensioner, just pressure to extend it and lube it.  As it wears and there is more clearance, and more oil can get around the plunger, the oil hole size actually begins to come into play.

 

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Hi srqjohnson.

The CCT's oil supply is purely to lubricate the CCT it is not a piston type (which I've experienced in cars) where oil pressure is forcing the plunger out, oil simply flows through it virtually unrestricted other than the orifice created by the gasket hole.

There is a fine line between an over and under tensioned cam chain and, as the chain stretches, the plunger is moved further outwards.

My thoughts are that maybe over time the spring tension within the plunger weakens, just enough to cause cam chain slap most noticeable in the upper cylinder head area. Others have stated that it's the CCT itself that is causing the rattle, but in both of the CCT's I've changed on a 6gen the noise of chain slap was very evident at the upper cylinder head area well away from the CCT's, simply replacing with a new CCT fixed the issue in both cases.

I've tried slightly unscrewing the CCT mount bolts moving the CCT backwards momentarily allowing the plunger to extend slightly then re-tighten the bolts thinking this could take up the slack, however, this was not successful.

I've thought about the non OEM manual units you can fit, but I'm very cautious of Over tensioning the chain as well as the need to adjust it in the future for chain slack. I've stuck with the OEM's

On removal you do need to fully retract the plunger, and, be very careful to withdrawal the CCT so as to NOT pop the steel cap off the plunger!!!!!

Just my 2 cents worth.

Cheers.

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Grum, Thanks, good info.  You are absolutely correct.  My theory about the oil pressure assisting made a lot of sense, as that is done in many engines, but not the VFR.    A quick test showed me otherwise.

 

For a sanity check, as my new one is not installed yet, I  took out the key, (you can hold the plunger in with one hand), and put the correct bolt with an o-ring in the keyhole.  My air nozzle on the compressor is tapered and fits into the oil hole just right, and applying air pressure had no effect.  You can feel it blowing out through the little vent holes near the plunger.

 

Thanks again, back to the drawing board.  I'd really like to know why we have to replace these things, especially given the calibre of almost all other things engine related from Honda.  I like this VTEC so much I replaced my Ford with a VTEC Acura.  Hmmm...I wonder if it is going to contract the CCT virus from the bike.   :-)

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On 4/25/2019 at 7:41 AM, srqjohnson said:

Grum, Thanks, good info.  You are absolutely correct.  My theory about the oil pressure assisting made a lot of sense, as that is done in many engines, but not the VFR.    A quick test showed me otherwise.

 

For a sanity check, as my new one is not installed yet, I  took out the key, (you can hold the plunger in with one hand), and put the correct bolt with an o-ring in the keyhole.  My air nozzle on the compressor is tapered and fits into the oil hole just right, and applying air pressure had no effect.  You can feel it blowing out through the little vent holes near the plunger.

 

Thanks again, back to the drawing board.  I'd really like to know why we have to replace these things, especially given the calibre of almost all other things engine related from Honda.  I like this VTEC so much I replaced my Ford with a VTEC Acura.  Hmmm...I wonder if it is going to contract the CCT virus from the bike.   🙂

A question on your test - I'm running from memory, so you'll have to excuse me if I am just misunderstanding - if spring tension is already holding the tensioner at full extension, what difference would your air test make? Any pressure would only assist the spring pressure.

 

For my part, I re-tensioned mine, enlarged the oil holes a tiny bit and re-installed. I haven't had any issues yet, but I also haven't put a ton of miles on since. Time will tell, but it certainly seemed logical when I had the parts in hand.

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Interesting tidbit from http://www.cbr1100xx.org - different bike,  but I'm pretty sure it's the same design cct

This resonant frequency thing could indicate why some people have constant issues with their tensioner and others have nary a problem. It may come down to how you ride and whether or not you spend a lot of time in certain RPM ranges.

 

Also, I'm especially amused by the last sentence...

 

984006548_Screenshotat2019-04-2611-57-16.thumb.png.ac4bc87e2a8a46c207d9eca8b04ce47d.png

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2 hours ago, Mohawk said:

Best answer = 1/2/3/4/5th gen Gear driven cams 🙂

 

Exactly how is "you should have bought a different motorcycle" a best answer? No offense man, but that's not really a helpful contribution to the discussion... unless you have a time machine, in which case fire that baby up and go convince Honda to make the 6th gen with gear drive cams!

 

I realize it isn't for everyone, but there's a lot things that I appreciate about my 6th gen... Unlike some, I like the linked brake ABS system. I appreciate VTEC conceptually from a mileage standpoint. I definitely prefer the looks...  If I can get all of that with gear drive cams and the 8th gen charging system, I'm all in!

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I'm sure Mohawk was just joking in a sense. He didnt say buy a different bike.... If you have hung around these forums enuff, you have figured out Mohawk is a top notch moto geek. 

I too have sworn off any Honda with a CCT and also have the gear cam drive addiction, but I'm open minded to learn something. I am finding this thread interesting. 

 

btw - some guys have built 6th gens with GDCs..

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I hear the cct noise on my 05.  It's definetly the front one.  I've put about 30K miles on it, all the while the noise comes and goes.  Some days it's louder than others, some does it's silent.  I want to replace it one day, but don't want to go through all this work if it's just going to come back(the noise).  I think if this engine blows up because I didn't replace the cct then so be it.  I got my monies worth.  

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On 4/27/2019 at 12:29 AM, squirrelman said:

no gear drive on gen 1 except for VF1000R

 

1st VFR in 1986 was gear driven cams, all others too, until 6th gen went back to camchain.  VF's are not VFR's.

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On 4/27/2019 at 1:27 AM, Marvelicious said:

Exactly how is "you should have bought a different motorcycle" a best answer? No offense man, but that's not really a helpful contribution to the discussion... unless you have a time machine, in which case fire that baby up and go convince Honda to make the 6th gen with gear drive cams!

 

I realize it isn't for everyone, but there's a lot things that I appreciate about my 6th gen... Unlike some, I like the linked brake ABS system. I appreciate VTEC conceptually from a mileage standpoint. I definitely prefer the looks...  If I can get all of that with gear drive cams and the 8th gen charging system, I'm all in!

I've looked at it conceptually & it "may" be possible to covert 6th gen to Gear drive. Alternately you could get a 5th Gen engine swap in there, like some 6th gen owners have done for just this reason.

The 6th gen camchain tensioner is a particularly poor design, by way of having the tensioner cap that can seperate when swapping the tensioner & fall into the engine :(

 

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Doh, I just read the last posts & yes it was a rib, rather than a suggestion. If someone can conclusively solve the 6th gen camchain issue, then that would surely be a good thing.

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30 minutes ago, Mohawk said:

I've looked at it conceptually & it "may" be possible to covert 6th gen to Gear drive. Alternately you could get a 5th Gen engine swap in there, like some 6th gen owners have done for just this reason.

The 6th gen camchain tensioner is a particularly poor design, by way of having the tensioner cap that can seperate when swapping the tensioner & fall into the engine 😞

 

I've been thinking about this off an on... Aside from the cap (which I agree is a poor design, but not really an issue if you wind the adjuster back in before you remove it), where are the issues? I know the VTR has a similar design and they can actually have catastrophic failure due to the tensioner, but do we have any real pattern to actual failures on the VFR? We all start worrying because of the noise, but what does the noise actually represent? Is it too much slack in the chain? If so, is it a matter of the spring not providing enough tension, or does the tensioner just not have enough throw to extend far enough?

 

Anyhow, the VTR guys have a solution that they refer to as the "Stopper mod" which is basically, just a little pill added inside the tensioner that stops it from backing off fully.

 

I know there are some that advocate manual adjusters, but this doesn't really seem like a good solution to me... I also don't plan to mod my bike to use carburetors, points or a kick starter.

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Thanks everyone.  Marvelicious:  You may have misunderstood about the spring in your post above.  It is never fully extended, and slowly rotates the screw inside the plunger to move the plunger out to compensate for wear.

 

Anyway, I changed mine and put in a factory fresh one and it cured my rattle.  That said, I am still at a loss as to exactly HOW it cured it.  I'm an engineer, though an electrical, with a lot of mechanical background, and aside from a scosh of available side to side wobble in the plunger on the old one, they both appeared to be identical.  The spring did not appear to be weaker or any other differences.  Also, the one I took out did not appear to be anywhere near fully extended.  

 

I had tried to count the turns to retract it, but working down in there with these clunky hands, just didn't allow the accuracy I envisioned on paper.  See exhibit below.  I have pictures of the plunger fully retracted, and fully extended, and the wear marks on the plunger shaft show it to be have spent it's life mostly only about one third extended.

 

Notes:  The factory key works, but is flimsy.  There is a reason there is a hole in it.

Possibly the hardest part was installing the new one with the gasket.  Believe me....there is no way the metal gasket will cooperate.  The clearance is tight and it will do everything possible to prevent your installing the new tensioner.  Any small misalignment stops you.

 

I decided to outsmart it by holding it in place, (SORT OF), with dental floss which I could remove when the time came.  The gasket countered by allowing me to install the tensioner, but rotating slightly so that the bolts were impossible to place.  I am now more appreciative of proctologists fees.  

I finally outsmarted and installed a bolt, as there is clearance for the floss and bolt in the hole and the rest was easy.

 

I had hoped to take pictures along the way, but in the heat of the battle, I just did not feel like it.  After the job pics below.

 

OEM_Key.jpg

Manufactured_Key.jpg

Retracted_Floss_1.jpg

Retracted_Floss3.jpg

Wear_Mark.jpg

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OK.  If anybody is listening....I had time to read through this whole thread, and follow the links.

 

The one post about the fellow putting in a screwdriver where the key goes and running the motor was interesting.  He observed the tensioner adjustment screw overcoming the spring tension, (which, is very light to begin with), and winding the spring, thus, loosening the tensioner.

 

Unbelievable, but we VFR people do not make this stuff up, and It might explain this whole thing I first started trying to understand, how the tensioner fails, if we can call it that, and how replacing one with what seems to be an identical part corrects it.  Above, I noted that the plunger in the one removed did seem to have a tad more play than the factory fresh one.  THIS might be just enough to allow the harmonics / vibrations to back the screw in over time.  It surely would be a pat explanation, especially in the absence of any other plausible cause.

 

Thanks again

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How timely that this is being (re)discussed.  I've "rebuilt" my CCT using the fore mentioned youtube video three times in the last 10k miles.  My rattle is back with a vengeance.  This time I'm just going to replace it with an new OEM unit.  I can't figure out why the rewinding process doesn't seem to work for me.  I can't imagine the spring tension of the rebuilt unit is significantly less than an new one.  Once I get the new unit, before I install it, I think I'm going to measure the amount of force the plunger delivers as compared to the rebuilt one.  I'll post up once done. 

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On 5/4/2019 at 5:31 AM, srqjohnson said:

Thanks everyone.  Marvelicious:  You may have misunderstood about the spring in your post above.  It is never fully extended, and slowly rotates the screw inside the plunger to move the plunger out to compensate for wear.

I did mine last fall, so it's been a while... that's right, there is no limit on throw. The tensioner would have to have traveled far enough to literally fall off inside... then the issue more or less has to be one of spring tension.

 

On 5/4/2019 at 7:42 AM, srqjohnson said:

The one post about the fellow putting in a screwdriver where the key goes and running the motor was interesting.  He observed the tensioner adjustment screw overcoming the spring tension, (which, is very light to begin with), and winding the spring, thus, loosening the tensioner.

Really, I think this is at least partially by design. The tensioner is supposed to be able to extend and retract within certain limits. That's the whole idea of this arrangement vs a simpler ratchet design. The trouble seem to be that at a certain point that spring is just too weak to keep as much tension on the chain as we would prefer. I wonder if we couldn't take the whole thing to a spring manufacturer and spec springs with a 25% higher rate... 

 

On 5/4/2019 at 5:31 AM, srqjohnson said:

Notes:  The factory key works, but is flimsy.  There is a reason there is a hole in it.

Possibly the hardest part was installing the new one with the gasket.  Believe me....there is no way the metal gasket will cooperate.  The clearance is tight and it will do everything possible to prevent your installing the new tensioner.  Any small misalignment stops you.

 

OEM_Key.jpg

Yikes... I made one out of a hardware store key blank and it worked like a charm. Seemed like better use of my time to start with a shape that was 80% already there.

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6 hours ago, Marvelicious said:

The trouble seem to be that at a certain point that spring is just too weak to keep as much tension on the chain as we would prefer. I wonder if we couldn't take the whole thing to a spring manufacturer and spec springs with a 25% higher rate... 

 

 

If anybody is up to experiment, if you have a loose spring, I could ask a local spring supplier I know to see if they would make a stiffer spring.... 

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If I had an old one, I'd happily donate... It really seems like a worthwhile endeavor. I'm no spring expert, but it seems likely that you could go a size larger on the spring wire and prevent future issues. 

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