Help on engine rebuild (what parts should be replaced)

[EnriqueM]

Hi all,
I have been lurking on this site for a good minute while planning and working on my build. It's a 1981 CB750k.

Sadly, the previous owner thought it would be a brilliant idea to chrome spray paint the outside of the engine instead of polishing the the slightly faded aluminium. Due to this, and me wanting to paint the engine anyway, it obviously needs to be cleaned thoroughly on the outside (I was thinking vapour blasting) before painting, and it seems the best way to do this would be disassembling the engine, have it blasted, cleaned and painted, and then put back together.

The bike is on 56 000 km (just under 35 000 miles), and was sitting outside for a couple of years before my purchase. So all of these factors combined, I thought I might as well rebuild it "properly" instead of just replacing seals and gaskets when reassembling.

I have a shop manual, and will be buying the Clymer manual soon to assist with the rebuild.

Finally to my question: What components should be replaced, what would be nice to replace, and what components would I need to inspect to know that I should replace them?

So far I have gotten the engine running, and nothing sounded weird. To get there I did a full carb rebuild, new carb intake boots, new ignition coils and plug caps, new spark plugs, new (to me) starter motor (mine was busted), oil change and a new oil filter. Pretty much the basics.

Keeping my question in mind, I was thinking I should replace the following to get the engine back to tip top shape for the next 40 years, so please do comment on anything that should be added to the list or isn't necessary:
- Engine gasket set
- intake and exhaust valves
- valve stem seals
- valve guides
- valve guide o rings
- valve springs
- cotter valve / valve keepers
- valve spring retainers ?
- Oversize pistons and rings (bore out engine at machine shop)
- clutch plates
- clutch springs
- clutch dampeners
- cam chains (both)
- cam chain tensioners and springs (both)
- cam chain guides (both)
- primary chain
- primary chain tensioner
- oil seal kit
- oil pump rebuild kit
- crankshaft bearing shells
- conrod bearing shells
- oil strainer screen ?
- stator
- tappet cover o rings

Thanks!

 

[Old_Crow]

With the exception of the gaskets, seals and the cam chains and tensioners I don't think I'd just preemptively replace any of that stuff without inspecting it first. A lot of that might be able to be cleaned or reconditioned which would save you a sizeable chunk of change which you could spend on stuff not on the list like tires, a final drive chain and sprockets, and possibly wheel bearings, swing arm bushings and steering neck bearings.
Also, if you really have the actual Honda service manual, I wouldn't waste money on the Haynes or Clymer books. They're better than nothing, but not better than the factory manual.

 

[mrtwowheel]

Put some oil in the cylinders (sparkplug hole), crank the engine by hand many times slowly after letting the rings soak some oil, check the compression of the cylinders, be sure the valve shims are somewhere close to spec (opening and fully closing).

I wouldn't order any parts till this was done. I wouldn't disassemble till this was done. Some of these engines just don't show any signs of wear.

 

[mrtwowheel]

The engine cases are originally painted, they are not polished aluminum. The engine covers were a polished alloy with clear paint.

 

[EnriqueM]

Appreciate the advice! I'll definitely open up the engine before ordering parts, and will test compression. If the compression is good would that indicate I do not have to bore out the cylinders but rather hone and keep standard pistons? Or would I need to inspect the cylinder walls after opening her up to be able to determine?

What I am gathering is that I should be able to get away with reusing allot of parts which is great, but I'll only be able to tell after I have a thorough look.

I am sure I will have more questions as I go, so I will be keeping the thread updated as I get into the engine.

 

[dirtdigger]

notorious for valves clearances being tight on these engines and burning valves and seats. Timing chain guides are terrible for falling apart and replacements are very hard to find

 

[EnriqueM]

I've heard some bolts should rather be replaced as well?