honda cb 500k1 primary chain

[alan]

anyone out there know what the primary chain length is for a 1973 honda cb500k1, mine seems to have had a go at the crank cases so it must be flapping about a bit! bit I can't find the wear limit length in any of the service manuals. If anyone had an original genuine honda work shop manual it may tell you in there.
cheers alan

[mickwinf]

its knackered you will need a new one! No tensioner so replacement the only option

[Nurse Julie]

As Mick says, the only option is to replace it. Good thing you got to it before it sliced through the main oil gallery.....very messy indeed 
Oh and fit new primary drive rubbers, false economy not to.

[bobv7]

How could I tell without stripping the engine down if the rubbers and chain might need replacing? I'm only asking because I don't know the full history of my bike as it's a US import and the mileage maybe inaccurate.

[Trigger]

You can't. If the chain is clunking at tick over usually means the chain and rubbers need replacing. I have built over 30 USA imported engines and everyone has rubbers as hard as rocks 

[K2-K6]

On the 750 there is a routine with measurement by vernier caliper from sump flange to the primary chain guide roller to judge the chain wear.

On the smaller engines they don't have the same sprung guide roller to do this.  But someone on here with more experience of those engines I'm sure will be able to describe this if it's possible on your engine.

It's most likely that the rubber components will need replacement.  They are subject to going hard just through living in hot oil in combination with general lifing in plasticity terms. It's probably in the order of 99% that they'll need changing if original.

[K2-K6]

Apologies, crossed over there with trigger while typing 

[Nurse Julie]

This is what Oddjob was referring to earlier in the thread. This is a CB400/4 Hyvo primary chain (same chain as fitted to the CB500/4). The knackered one on the left has about 5000 miles life left in it as you can see by the middle of the chain touching. The one on the right is new.
But...you have to remove it from the engine to assess its knackeredness 😀😀 Once you have removed it to assess, you may as well fit a new one whilst you are there, no point in not changing it and false economy not to either.
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