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Discussion Starter #1
I've seen on car shows before that mechanics will fit new harder valve seat in the heads of cars that were designed for leaded gasoline. They say if you run unleaded gas in an engine designed for leaded gas it will prematurely wear out the valve seats. Is that true with our bikes (mines a '78)?
 

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I don't know about the CX's, but my 1973 Honda Civic had hardened valve seats suitable for unleaded fuel.
 

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Unleaded fuel has been available since the mid-70's.

The zinc in fuel was mainly for valve guides and other parts with sliding movement in the fuel/air mix path. Very little movement between the seat and the valve.
 

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Discussion Starter #5
Thanks Murray.
 

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From reading loads of old classic car mags in the 80's it was suggested by the wise, that old engines that had already done a lot to miles would run well with unleaded as the valve seats would....In my words... become work harder with the lead rich fuel previously. Now what would happen to an old set that have been re-cut or aggressively lapped? Not sure.
However. My CX engine is having her valve seats re-cut at the moment and I'm pretty sure all the wise ones will say CX seats are already hardened.I gave up lapping mine too much to do and not enough time. I guess even with hardened seats a bottle of unleaded additive every now and again wouldn't go a miss.... Or money down the drain. I'm assuming even harden seats can wear otherwise I wouldn't be now having all mine done due to pitting on the exhausts.
198802
 

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I've cut a few now. It must only be the exhaust seats that are necessary to harden. They are really hard - but not the inlets.

I've scraped a 4th angle into the inlets a few times now with a knife blade. The exhausts are impervious to the knife. :)

Your exhaust look pretty bad, but likely salvagable. Rust I'd say. The seats seem to burn between the exhaust valves and where they face the sparkplug.
 

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Discussion Starter #8
I'm getting ready to pull my engine apart, hope the heads don't look that bad... Hopefully your's will clean up nicely.
 
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