Cam chain tensioning, isn't this a misleading idea ?

I'm reading about the manual cam chain tensioner, and how to set it, and I'm thinking, those 15 links it says in the manual when the cams are aligned, if the chain is even slightly worn, there's no way those cams will be correctly timed, no way those arrows will be pointing 90 degrees upward, and the more you stretch the chain, the worse it gets, so a cam chain is really a case of zero tolerance, either it's perfect or it's scrap, so what's the point of tightening it, you'll only be increasing your valves' mistiming, or am I wrong ?

Edited by michaelks

I'm reading about the manual cam chain tensioner, and how to set it, and I'm thinking, those 15 links it says in the manual when the cams are aligned, if the chain is even slightly worn, there's no way those cams will be correctly timed, no way those arrows will be pointing 90 degrees upward, and the more you stretch the chain, the worse it gets, so a cam chain is really a case of zero tolerance, either it's perfect or it's scrap, so what's the point of tightening it, you'll only be increasing your valves' mistiming, or am I wrong ?

I'm thinking the amount of stretch that occurs is really a small % of the overall chain length and you wouldn't see any difference in where the arrows are pointing. But a stretched chain would affect performance, and be noisy too boot. How much performance would be lost I don't know.

Ron W.

I'm thinking the amount of stretch that occurs is really a small % of the overall chain length and you wouldn't see any difference in where the arrows are pointing.

Not correct, it is very noticeable.. and often causes confusing when someone is looking at the service manual as there only point of reference and working on a motor with a worn cam chain

I'm reading about the manual cam chain tensioner, and how to set it, and I'm thinking, those 15 links it says in the manual when the cams are aligned, if the chain is even slightly worn, there's no way those cams will be correctly timed, no way those arrows will be pointing 90 degrees upward, and the more you stretch the chain, the worse it gets, so a cam chain is really a case of zero tolerance, either it's perfect or it's scrap, so what's the point of tightening it, you'll only be increasing your valves' mistiming, or am I wrong ?

Close, and good thought process...But Not quite..

1: the pin count is only usable on OEM cams.. not for any aftermarket ones.

2: You kind of get it.. as the chain wears and becomes effectively longer pin to pin.. the cam marks will no longer line up perfectly.

 a deg or so not a huge deal..and you can see it off that much in a few thousands miles.

3: Yes, if you are building a motor you want max performance from, and have dialed in the cam timing,,you will want to use a new chain and MCCT.

I'm reading about the manual cam chain tensioner, and how to set it, and I'm thinking, those 15 links it says in the manual when the cams are aligned, if the chain is even slightly worn, there's no way those cams will be correctly timed, no way those arrows will be pointing 90 degrees upward, and the more you stretch the chain, the worse it gets, so a cam chain is really a case of zero tolerance, either it's perfect or it's scrap, so what's the point of tightening it, you'll only be increasing your valves' mistiming, or am I wrong ?

 

Cam timing will change as cam chain wears, though it's not enough to be of concern to internals.....

Your cam chain adjustment will be well past it's maximum wear limit before it becomes an issue

Cam timing will change as cam chain wears, though it's not enough to be of concern to internals.....

Your cam chain adjustment will be well past it's maximum wear limit before it becomes an issue

 

It would seem that the tensioner knows no such limits, as it can extend quite a bit against the chain guide as the chain wears, in fact unbeknownst to the owner (automatic) or by his own action, tightening along like a transmission chain. I wonder if many instances of "cam chain skipped a tooth" aren't really just the result of advanced wear, made visible when the cover is removed and the sprockets are seen to be pointing away from one another.

When I checked the before and after cam timing (old vs new chain) with degree wheel, I found the old cam chain had allowed the cam timing to retard about 4 deg.  That might be significant for a race motor but not very noticeable for a daily driver.

i never understood why they said to set it at TDC to set the install the mcct

i never understood why they said to set it at TDC to set the install the mcct

 

When the cams are at any point but TDC on the compression stroke, one or more lobes are pushing down on a valve bucket.

 

When you release all tension from the cam chain, the cams can rotate under force from the valve spring.

 

This could cause the cam chain sprockets to skip a tooth on the chain.

When I checked the before and after cam timing (old vs new chain) with degree wheel, I found the old cam chain had allowed the cam timing to retard about 4 deg.  That might be significant for a race motor but not very noticeable for a daily driver.

 

The cam sprocket seems to have around 40 teeth, so 4 degrees would be say half a tooth skipped. Still surprising this shouldn't have much effect.

 

By the way, does the cam chain dip into the sump oil in this dry system ? Where it does, it has no wear at all, I'm told.

When the cams are at any point but TDC on the compression stroke, one or more lobes are pushing down on a valve bucket.

 

When you release all tension from the cam chain, the cams can rotate under force from the valve spring.

 

This could cause the cam chain sprockets to skip a tooth on the chain.

 

In connection with that, I remember reading somewhere about the intake valve spring, when closing the valve, causing the intake cam to rotate forward faster than the exhaust, causing a constant tightening/slackening of the chain between sprockets.

Edited by michaelks

When the cams are at any point but TDC on the compression stroke, one or more lobes are pushing down on a valve bucket.

 

When you release all tension from the cam chain, the cams can rotate under force from the valve spring.

 

This could cause the cam chain sprockets to skip a tooth on the chain.

 

 

i put my mcct on and off over 10 times since i got the bike, and never installed it at TDC,,, woops :lame:

 

should i go fix it..

 

cool down bike, loosen mcct, set to tdc, set mcct again??

Edited by 707LAKE

 


The cam sprocket seems to have around 40 teeth, -----No.  Fewer. And remember the cam turns at half crank speed.  When "degreeing" cams to a specific location, 4 deg is enough that a tuner would make a change for optimum performance.  However, to the seat of the pants dyno, it is not very noticeable on a standard motor


 


By the way, does the cam chain dip into the sump oil in this dry system?---- No. (and I hope not).  That would be a lot of unwanted drag.


 


Where it does, it has no wear at all, I'm told.---- I call BS on that.  No cam chain intensionally dips in the sump oil and there is no such thing as "no wear at all"




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Edited by Noble

707 - No.  If nothing bad happened during instal, it is fine.  I assume you adjusted it to eliminate the chain rattle so it should be good.  If you are suddenly worried about it you could check the timing marks (cams vs the TDC mark)

I measured (15 links of) a worn CC once and a new one.

The worn one was longer indeed.

Then i counted teeth etc, calculated the total difference and how auch that is in teeth.

I arrived at 3 degrees retard at ex, intake a bit more.

That is visible at the deck/timing marks.

 

The ACCT stretches/wears chains way faster then MCCT.

My chain holds up extremely nice with MCCT and Full Synth Ester based oil.

I measured (15 links of) a worn CC once and a new one.

The worn one was longer indeed.

Then i counted teeth etc, calculated the total difference and how auch that is in teeth.

I arrived at 3 degrees retard at ex, intake a bit more.

That is visible at the deck/timing marks.

 

The ACCT stretches/wears chains way faster then MCCT.

My chain holds up extremely nice with MCCT and Full Synth Ester based oil.

 

The excessive tension of an ACCT will definitely increase wear rates for cam chains

 

 

The cam sprocket seems to have around 40 teeth, -----No.  Fewer. And remember the cam turns at half crank speed.  When "degreeing" cams to a specific location, 4 deg is enough that a tuner would make a change for optimum performance.  However, to the seat of the pants dyno, it is not very noticeable on a standard motor

 

By the way, does the cam chain dip into the sump oil in this dry system?---- No. (and I hope not).  That would be a lot of unwanted drag.

 

Where it does, it has no wear at all, I'm told.---- I call BS on that.  No cam chain intensionally dips in the sump oil and there is no such thing as "no wear at all"

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Yes, after doing the primary and counterbalancer loctite fixes I could see the chain sprocket is way above the sump oil level...but then, where does it get its oil from ?

The excessive tension of an ACCT will definitely increase wear rates for cam chains

 

I'm not so sure of that, mine makes a normal chain rattle, quite against the silencing people report after adjusting the manual tensioner. Anyway, the automatic tensioner can become a manual one, just by removing the spring and adjusting as needed, albeit a little more difficult to do because you'd have to remove the tensioner for each test.

 Anyway, the automatic tensioner can become a manual one, just by removing the spring and adjusting as needed, albeit a little more difficult to do because you'd have to remove the tensioner for each test.

 

... please let us know how that works out for you...

... please let us know how that works out for you...

Right now I'm trying to collect more information as to the claim that the automatic tensioner puts too much stress on the chain, after that I'll ratchet it down one tooth and remove the spring. But not so much because of the spring itself, but because this type of tensioner works irreversibly, so on the hottest summer day and under heavy use it's conceivable that the chain will have a thermal slack that will cause the spring to ratchet the tensioner up a tooth or two, which in turn will mean over-tensioning on a cold winter day. Maybe that's why people have sometimes found the chain to be over tightened (during a winter overhaul, probably). But that might happen also for the manual tensioner if folks notice more chain noise when it's hot and adjust accordingly. Only a spring would be best, as Cal-tony suggested in another thread.

Right now I'm trying to collect more information as to the claim that the automatic tensioner puts too much stress on the chain, after that I'll ratchet it down one tooth and remove the spring. But not so much because of the spring itself, but because this type of tensioner works irreversibly, so on the hottest summer day and under heavy use it's conceivable that the chain will have a thermal slack that will cause the spring to ratchet the tensioner up a tooth or two, which in turn will mean over-tensioning on a cold winter day. Maybe that's why people have sometimes found the chain to be over tightened (during a winter overhaul, probably). But that might happen also for the manual tensioner if folks notice more chain noise when it's hot and adjust accordingly. Only a spring would be best, as Cal-tony suggested in another thread.

 

 

i doubt there is 20F difference in engine oil between summer and winter. since the chain is splashed with that engine oil, is 20F going to make it stretch enough to vary between tight/loose ? i doubt that also. 

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