If you can get to hear it on low revs pull the clutch in, does the sound get better? If so that bit was the clutch, they all do that, run it and balance the carbs to get rid of 50% of the noise, the chains will still rattle. As previous post drop the sump tray off and measure the primary chain deviation as per Honda spec.
If your luckly the chains will be in spec and the culprit is the lower chain tensioner, I think you can replace this from the sump, I'll check tonight as Im splitting a motor in my workshop now. But for the cost its often better to do this anyway cause once they are in the oil/heat they harden off and become less effective.
If chains are out of spec a little way don't panic, source genuine honda chains and get ready to pull the motor, they certainly built them heavy but they are not complicated it just takes a lot of time.
Best thing to do is if you have a camera keep taking shots in the tear down. Lay out any fixing pins in a patern like the holes they go in and take a shot ( this saves sticking too short/too long pins in the wrong place ) or press the casing onto card mark run with a pen and push the pins through positions in the card to give you a template.
Make sure every thing is a clean as possible before you pull the motor and after, dont open it up until the outside is clean because you are going to have to take the shells off the crank dirt will kill them.
You will need a full gasket set, dont use anything else but grease on them unless Honda state other wise Ive seen 2 many snapped/knackered cams caused by red hermitite used on the cylinder gaskets hardening and finding its way into the oil restrictor jets that feed the cams.
If your used to working on Jap engines you can get away with hand torqing most pins except the shell bearing caps. You need an accurate low level torque gauge for the main bearing clamps when you come to rebuild.
And you may choose the spray the cases silver, use Holts or Simonise spray tin called "Steel Wheels" from car shops check out my other post on how to. I will be photgraphing the tear down I am doing now so I can post.
When you have done all this it will still sound rough on tickover compared to a modern 4 but like the sying goes "they all do that sir" but remember if the chains are out of spec it needs doing some time, if they are in spec put that sump back on and leave well alone I don't belive in disturbing shell bearings unless you really have to.
Cheers
Graham
