Topic: primary chain wear limit

[turboguzzi]

trying to find the wear limit for the primary hyvo chain in a 500...

does anyone have a clue, say max allowed distance between 20 links or something like that?

thanks

TG

[scunny]

not sure if it helps but with the 650 hyvo primary you are meant to place the chain over the 2 sprockets, tension to 32 kg and measure the distance between the 2 sprockets. max allowable 115.5mm

[bryanj]

There is no spec for the 500/550 in the book, with sump off feel if chain is wearing a groove in the oil gallery using highly specialised honda mechanic tool called a forefinger

[dave500]

yeah its a grey area,if its apart and done many miles its worth updating it.

[Deltarider]

Do they wear? Mine is in there over 130.000kms. I have always learned it was in fact overdimensioned and that the same chain was found in Chevrolets of that time, although I don't know for what purpose. Maybe someone remembers.
Wish Honda had used some better material for the camchain tensioner, which is, in my view, the crappiest part in the engine.

[dave500]

if that chain is in chevys id like to find out what one,air cooled corvairs?the same type but not the same one has been used for the camshaft drive in small blocks,ford windsors aswell.

[turboguzzi]

Thanks guys,

well, they do wear, the one in my racer was lightly touching the oil gallery and got changed, new one was much tighter.

Was looking for the wear data for a 750 kawi i am doing, it's got an hyvo chain too, but no wear limit specs in the shop manual, was hoping to find something like allowed length for X links, its info that's easy to find on regular chains.

strange, but all my searches (kawi forums included) have not yielded much info on hyvo's wear limit,

as hyvos are sort of self adjusting when under load, seems like a bit of a gray area 
 
TG

[dave500]

it might be because regular chains can be laid out along their entire length,where as a hyvo is a looped affair and harder to measure in this respect?the sideways bend is my guage,if any chain goes sideways a lot its buggered.

[Bodi]

They are used as cam chains in quite a few car engines (well, many millions if you count each one rather than each type). In car engines with these chains the chain is considered a lifetime part. Now that toothed belts are common there's a replacement schedule which you better follow if you have one where the valves would hit the pistons should the belt fail.

[dave500]

which most will,its only done for a noise factor,and an inbuilt obsolence factor,its also done as a weight factor,so new cars can be loaded up with electronic gissmos in the place of a proper chain.

[bwaller]

I always suggested to customers when the chain seemed noisy it was time to synch the carbs.  If it was still noisy afterwards it was time to replace the chain.

Maybe instead of measuring physical length we should use a stethoscope and develop a "rattle guage".

Ok all nonsense aside Bryan's Honda finger approach is the only way to really know if disaster is looming. I never saw a chain come apart but they do stretch.

[turboguzzi]

after much googling, found some stuff.

the kz650 manual (essentially the same bottom end) specifies 27mm up and down "chain slack" with the shafts installed.

the other one is from a Borg Warner/Morse document, and its quite interesting:

"Chain Elongation: Even though Morse Hy-Vo Products are built to last, when the rebuilder has
the unit down, the sprockets and chain should be checked thoroughly.
Remember that it is very difficult for the aftermarket customer to measure chain elongation. One
reason for this is shaft movement when the unit is apart. In certain cases, when the shafts are
fixed with the cover off, an experienced field estimate may be acceptable.
Morse has special equipment to measure elongation parameters. In addition, each application
could be different depending upon the application parameters.
The accuracy rate or error rate is 50% without using the right equipment to measure elongation
of a chain. Every application has its own variations and the manufacturer’s recommended
specifications for chain tolerances should be referenced."

Very PC.... Guess that explains the lack of solid figures on the subject.

That said, has anyone heard of a hy-vo chain failure in a small sohc? I changed the one in my 500 only so it wont cut the oil gallery open, but looks like other than that, they do last forever or almost. there's no rubbing problem in that kawi motor....

[bwaller]

Looks like you can save all the old Honda chains for the K brand. 

I never saw a primary chain fail in these engines. Paulages had a new 650 camchain problem though.

[bryanj]

Seen several Hy-vo cam chains fail in 250/400 N & T models, never seen a primary fail but seen several worn 500 crankcases although none worn through

[turboguzzi]

not surprising.... hy-vo cam chains dont have the split pins that drive hy-vo's have, hence wear more....