Cam chain replacement

[MikeinNZ]

Hi all,

Thought I would share what a 100,000 kilometre cam chain looks like.
2 photos of the new and old chains comparing the stretch of the old chain.


There is no service schedule for replacement that I could find but at $60 thought it was worth replacing.
Trigger wheel, rear chain guide and cams have to come out so a fairly big job.
Engine is notably quieter.

 

[RCinNC]

I don't dispute the idea of changing one, but I believe the intent of the designers is for the chain to last the life of the engine. My Toyota Camry has a timing chain (not a belt), and there's no recommended interval for that to be changed either. The problem with things like chain and sprocket combinations is that the two of them wear at the same time; when you change a chain, you should change the sprockets (in this case the camshafts containing the camshaft drive gears) that are driven by the chain. With a brand new chain on a worn sprocket, it can actually accelerate wear.

I thought about doing this myself at my next valve check, and decided against it due to the expense/aggravation of swapping the cams along with the chain. I don't think I've ever heard of anyone breaking a cam chain on the S10, or even on a cam chain equipped car.

Then again, I have 79,000 miles on my S10, and fate might make me eat my own words.

 

[thughes317]

Curious as to reason for replacing? There is no mention what-so-ever in factory service manual for inspecting/checking wear on cam chain (as RC mentioned, it's designed to last the life of the engine). There is an inspection procedure for camshaft sprockets but if they are worn out of spec the cam sprockets, timing chain, and crank sprocket are to be replaced as a matched set.

 

[MikeinNZ]

I have been chasing a noisey valve train for a while now. I have checked the clearances twice now over 40,000 kms which were fine both times.
Apart from the chain stretch there was no wear on the sprockets so no problems accepting the new chain.
The camshaft journals and caps were perfect with slight wear on the lobes. It’s still in good shape internally which is a bonus as I intend to ride it till it stops.
Like I said, it’s noticeably quieter so I’m happy.

 

[blitz11]

GM started with those Hy-vo chains in 1965 with the Toronado and Eldorado THM 425 (I was an engineer there in the 1980s), and those chains and sprockets lasted forever (and those were built to a relatively low cost). That chain was developed by Borg-Warner as an alternative to a roller chain, both for durability and reduced acoustic emissions.

The pins and links are cool, too. Not round.

If you look at the spacing of the plates, every other plate rides on the sprockets, halving the wear when compared to a conventional roller chain. that's one reason that the sprockets and chain last so long.

 

[RonH]

Any manual will say replace the sprockets and chain together if you do replace, but the fact is cam sprockets and the teeth on the crankshaft never wear. The chain will eventually wear causing cam timing to be slightly wrong and eventually the tensioner will no longer have any more range to tighten the chain. Also the chain could break, but even a new one could, but rare either way.
I had a buddy with a 1979 Honda CBX back in 1981 and I don't think that motorcycle even had 5000 miles on it, and one day he was sitting at idle and the camchain snapped and he bent 18 valves.
I replaced the chain on an old 1978 Kawasaki that had 160,000 miles on it and the sprockets were still good as new.

 

[thughes317]

Any manual will say replace the sprockets and chain together if you do replace, but the fact is cam sprockets and the teeth on the crankshaft never wear. The chain will eventually wear causing cam timing to be slightly wrong and eventually the tensioner will no longer have any more range to tighten the chain. Also the chain could break, but even a new one could, but rare either way.
I had a buddy with a 1979 Honda CBX back in 1981 and I don't think that motorcycle even had 5000 miles on it, and one day he was sitting at idle and the camchain snapped and he bent 18 valves.
I replaced the chain on an old 1978 Kawasaki that had 160,000 miles on it and the sprockets were still good as new.

Interesting...because the FSM does advise checking cam sprockets for wear and gives a diagram/wear specs. No dog in this fight, just wondering why Yamaha would include that?