Cam chain replacement schedule?

[bclark]

Just reading 3PatCs comments Clem's engine thread (General) about Oafish behaviour and it made me wonder what is the replacement schedule is for a cam chain? - Has anyone has ever had one let go (or a primary chain for that matter).. at what mileage?

Also do intervals extend with a modern chain specs?

 

[andychain]

Brian cam chains should last for tens of thousands of miles and it is best to leave them
as the sprockets will have worn with the chain. I have always been amazed at how often
Laverda owners change components that should last longer, the primary is another example.

For cam chains it is important to get automotive chain not industrial, although in most
cases a high quality industrial will do fine.

In the main automotive chains have a different material spec that includes chrome which
gives a better wear life.

For the sake of around ?20 and a chain that is relatively easy to fit peace of mind is cheap.

Andy

 

[CLEMTOG]

could'nt agree more with Andy
I always keep a replacement timing chain from Andy on the shelf,this is an Iwis and has split rollers, which some will say is not good,maybe so, maybe the solid ones are better, but the split roller seems to be perfectly good enough to me, my experiance is that the last one I changed had done 40,000 miles, I tried very hard to compare the old chain with a new one, before fitting, I did a stretch test side by side on a steel topped bench and realy could not tell the differrenc between the new one and the old one.

Same thing at the same time, I bought the last iwis triplex primary that Andy could supply, and compared it with the old one,same mileage, same test, very difficult to see why I was bothering,

the Merc timing chain (in my Merc diesel) is original at 240,000 miles, if it snaps I will scrap the rusty old pig, if it doesnt I will continue.
CLEM

 

[Dellortoman]

My brother's 1975 3C is still on its original Regina chains at something like 70,000km. Some of you would have seen his bike at BSFOS 2011. It's a bit of a ratty looking thing, but he likes its patina, so has no intention of tarting it up. I just went out to the shed and checked the mileage (it stays in my garage because he's a hillbilly and lives in a rotten hollow log somewhere in a dark forest) and yes, it's near enough to 70K, actually 69,800km.

When I was doing some maintenance on it a while back (yes, I'm sometimes his mechanic as well his garage keeper), I asked him if he wanted me to replace the chains because I had some Andychain replacements in hand (thanks Andy). We measured the stretch on the existing chains and it was bugger-all, so he told me to leave the original chains in it. He suggested we should check them again at 100,000km.

Given that there was almost no measurable wear on them at 70,000km, I suspect the 20,000km replacement schedule for primary chains may be erring on the safe side.

Cheers,
Cam

 

[bclark]

Well this restores my faith in all things mechanical. I have to say I have never replaced a cam chain outside of a full engine build (where everything is worn out). There is so much talk of chain swaps on here it just got me wondering if I was missing something..

 

[3patC]

I just used to change them as dictated by the factory handbook Brian. I thought they would know more than most about it so I just followed their advice. I snapped several rear chains though until Renolds Grand Prix chain became available and that problem was solved (for me at least).