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Discussion Starter #1
I have a general question. What kind of mileage can be got out of cam chains and tensioners assuming they have been properly maintained.

15000 mi
20000 mi
25000 mi
30000 mi
45000 mi
50000 mi?


I did a triple bypass once on a bike that had 19000 miles. I replaced both the chain and the tensioners with new OEM. The tensioner I removed looked to be in very good shape when compared with the new OEM ones.

This leads me to the question of whether or not they actually needed to be replaced.


Also, if cam chains go 40,0000 plus miles, is there really a need to do this update at 20000 miles.

What about putting on a new chain and leaving the tensioner in?
 

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From my cursory readings on the forum (not from my own experience) it seems that a well maintained engine with regular chain adjustments, the chain would generally live 30-50k miles, if not more. I would expect the tensioner/guide to do the same.
In regards to early replacement, it's never a bad idea to get fresh......and if the old ones are still quite serviceable, I might be inclined to hang on to them for that "rainy day".
 

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I'm still using my original (post recall) tensioner and guide at just over 50k. Replaced the chain two winters ago, with about 40% left. I'm the second rider of this bike, and the original owner kept up the maintenance.

This is on a Standard, though​, not a Turbo.


R
 

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I've done 95.000 km and I still have the original tensioners. They look very good after so many years. Think they last forever:rolleyes:
 

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I can't say for sure about Turbos but I have heard of a few normally aspirated examples that have had camchains last well over 100,000 miles. All were in places where bikes are not parked for half of every year and were used regularly by the same owner for many years.

I read somewhere that one of the reasons some motorcycle camchains become worn out at relatively low mileages is that when the bike is not used for extended periods the pressure of the valve springs can cause only the part of the chain that is under tension to stretch. When you begin to use it again the stretched part causes the tension to vary as the chain rotates which hammers the tensioning mechanism and causes increased stresses on the rest of the chain.

If you have a 30+ year old bike that has only gone 20,000 miles it is a pretty good bet that it has sat unused for a long time at least once in its life.

As for re-using the old tensioner blade, check whether the rubber has hardened. I figure if I can make a dent in it with my thumbnail it is probably soft enough to last a few more years but if it has hardened it has probably become brittle too.
 

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I can't say for sure about Turbos but I have heard of a few normally aspirated examples that have had camchains last well over 100,000 miles. All were in places where bikes are not parked for half of every year and were used regularly by the same owner for many years.

I read somewhere that one of the reasons some motorcycle camchains become worn out at relatively low mileages is that when the bike is not used for extended periods the pressure of the valve springs can cause only the part of the chain that is under tension to stretch. When you begin to use it again the stretched part causes the tension to vary as the chain rotates which hammers the tensioning mechanism and causes increased stresses on the rest of the chain.

If you have a 30+ year old bike that has only gone 20,000 miles it is a pretty good bet that it has sat unused for a long time at least once in its life.

As for re-using the old tensioner blade, check whether the rubber has hardened. I figure if I can make a dent in it with my thumbnail it is probably soft enough to last a few more years but if it has hardened it has probably become brittle too.
The whole concept of chain stretch is a misnomer. The chain wears where the rollers slide against the plates, causing an incremental lengthening at each junction. Sitting still cannot affect the chain unless the valve springs can push the chain beyond its yield point. Very unlikely.*

Of course sitting could affect the tensioner as you describe. That's something I didn't know I had to worry about. Hopefully things are OK in there...

*I've wondered about claims of old fork springs not working right if the bike just sits. Same thing. I have the feeling that these bikes were simply sprung very soft. ???

Peter
 

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When the chain is under tension the pins will be held against the rollers and the holes in the plates; in the real world nothing ever really sits still but is constantly vibrating so the parts are constantly rubbing against each other. That won't cause any significant wear over 6 months but over 5-10 years it can.

As I said, the examples of very high camchain life that I have heard of were all in machines that were used regularly, year round and never stored for extended periods......
 

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So would it be a good idea to take the tension out of the cam chain when storing the bike? Over winter or longer term storage?
 

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Over the winter probably wouldn't make a great deal of difference since it is not very likely that the same part of the chain under tension again next winter. Storing it for a decade on the other hand...
 

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Discussion Starter #10
I can't say for sure about Turbos but I have heard of a few normally aspirated examples that have had camchains last well over 100,000 miles. All were in places where bikes are not parked for half of every year and were used regularly by the same owner for many years.

I read somewhere that one of the reasons some motorcycle camchains become worn out at relatively low mileages is that when the bike is not used for extended periods the pressure of the valve springs can cause only the part of the chain that is under tension to stretch. When you begin to use it again the stretched part causes the tension to vary as the chain rotates which hammers the tensioning mechanism and causes increased stresses on the rest of the chain.

If you have a 30+ year old bike that has only gone 20,000 miles it is a pretty good bet that it has sat unused for a long time at least once in its life.

As for re-using the old tensioner blade, check whether the rubber has hardened. I figure if I can make a dent in it with my thumbnail it is probably soft enough to last a few more years but if it has hardened it has probably become brittle too.

********************************************************************************************************************

The good thing about these bikes is that they did not sit. They were a father/son pair and got ridden occasionally. Keeps things lubed up. The tensioners on these look excellent. Incide they are really clean. I have some other bikes that have sat, we will see what they look like.

The worst thing you can do in my opinion is to not run a motor and to leave a machine sit. I have way more issues with the low milage bikes I pick up than ones that have been middle milage, but have been run occasionally to keep the parts moving and lubricated.

Thanks for all the input everyone.
 

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Mine sat for 19 years, and I could still be using the original chain, if I hadn't gone in to change the alternator.

Chains wear prematurely because they aren't kept properly tensioned. If you have a low-mileage barn-find with a wrecked cam chain, the chain was worn out before it went into the barn. The original owner just didn't keep up the maintenance.


R
 

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It is also possible that your camchain could have failed shortly or damaged the tensioner if you had not replaced it when you did the alternator. As I said, when a section of the chain becomes "stretched" after sitting for many years it can hammer the tensioner as the tension varies when the loose section passes the tensioner.
 

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I had already been in the engine 7 years earlier, and left the chain in place then. There was no additional wear indicated by the adjuster, but I happened to have a new chain on hand the second time.

If a chain will stretch (exceed its yield threshold, as stated by Peter above) loaded only by the valve springs, it would never resist deformation in normal operation.


R
 

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So would it be a good idea to take the tension out of the cam chain when storing the bike? Over winter or longer term storage?
Don't let Bob scare you into unnecessary work. Even for long-term storage, just make sure it has clean oil and fresh coolant, and protect it from corrosion. Then carefully verify lubrication when it's brought back into service.


R
 

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Could the problem with long term storage be from deformation of the guide or tensioner when under the pressure from chain tension rather than chain "stretch"?
 

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It is a different form of stretch than you guys are talking about, more like the way a chain stretches from wear. I guess it is hard to understand if you don't have a good grasp of acoustics & vibration.
 

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I assume that "stretch" comes from either an increase in the size of the hole in the side plates or a decrease in diameter of the pins?
 

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Motors stored long term are best rotated by hand or spun on the starter motor rather than actually started. Every time you start the motor you put acid combustion byproducts into the oil. If only run up to operating temp and shut down they do not get burned off and blown out the breather. Periodic starting of motors in long term storage does more harm than good IMHO.
 

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Discussion Starter #20
here is the old chain (20,000 miles) versus new chain.



0.0835 inch stretch in old one = 5/64 inch = 2.12 mm. I wonder if you measured numerous new ones what the standard deviation would be. When on the sprocket, without tensioners, you could not even tell the difference. The amount of slop seemed the same.

 
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