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Discussion Starter · #1 ·
Hello all! So I'm not new to vintage motorcycles, but this is my first time working on an old Honda.

I recently bought a 1974 cb450. I'm in the middle of a full restoration of my 1975 rd350, but wanted something to cruise around on while the weather is nice. Found a nice guy nearby with what I was led to believe to be a turn key cb450. After riding it about half an hour home, I found a gaping oil leak at the cylinder base.

A little annoyed but still optimistic, I tried retorquing the head bolts. The leak still persisted. So, seeing as it also burned a little oil, I decided to pull the motor and referesh the top end.

So far I've managed to replace the points, hone the cylinders, lap the valves, clean off all of that obnoxious carbon and clean out the oil slinger (which looks like it had never been touched).

Tragedy struck when I went to replace the piston rings, only to find that they were a rather unusual size. Looks as though they were bored out 3mm over (through the help of this forum I sourced some nos rings that should fit). I'm not quite sure whether this was for performance improvement or they just kept oversizing their pistons. Any input on this would be greatly appreciated.

Anyways, I've still got a little work to do on the electrical. The previous owner doesn't seem to be to capable with a soldering iron. As well as replacing some more of the ignition components. Then reinstall the motor and get back to riding.

I just want to say what a pleasure it's been working on a Honda. Everything is so we'll thought out. It all just makes sense.

Thanks for reading through my long rambling intro. I look forward to getting to know you guys and learning a little bit more about keeping this old girl running right.
 

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Welcome... did you determine where the oil leak came from? A lot of these engines have been run with loose cam chains for a long time and many have some, if not a lot, of wear in the tunnel area between the cylinders and some have been known to wear through, eventually causing a serious leak. Be sure to look for chain wear areas in the aluminum between the cylinders, both front and back.
 

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That's very good to know. I believe that leak was coming from the oil channels on the left side of the motor. Right where the cylinder meets the crankcase. You could almost watch it drip out. I'm hoping new gaskets and copper washers will take care of the issue.
 

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Was looking at last pic, it looks like it was leaking from cam chain adjuster housing. Just guessing. That chain wear your talking about, is that because of double cams relation being outbound of base? So when there is slack in the chain, it falls outward and saws into case?

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That's very good to know. I believe that leak was coming from the oil channels on the left side of the motor. Right where the cylinder meets the crankcase. You could almost watch it drip out. I'm hoping new gaskets and copper washers will take care of the issue.
The only passage that might be causing it on that side is the far end of the oil gallery under the upper right part of the alternator housing gasket (not the 3 screw timing cover, the big one behind it). There are no oil passages between the upper case and the left side of the cylinder base gasket area, only on the right. I've never seen a copper washer on the 2 right studs leak oil and I've always re-used them. DOHC has nothing to do with the cam chain wear, the 350s do it too when the chain is improperly adjusted or neglected... the slack in the chain is enough to allow it to slap against the cylinder tunnel, usually at the front but I've seen it in the back as well
 
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