Valve guides

[CeeBee72]

Has anyone made valve guides for the CB72?
Interested in materials and method and success.

[DJM]

Personally I've never had any particular problems with the standard ones even when racing years ago but they are probably N.L.A. now.

If you make new ones it shouldn't be too difficult, I think aluminium-bronze is the clever stuff to use, apparently 'better' than phosphor-bronze which was the preferred material years ago, sorry but can't say what spec. / grade. Important details are obviously interference fit in the cylinder head and running clearances which again will depend on what valves you are running.

Lots of specialist companies around who should be able to give more detailed advice.

[CeeBee72]

Thanks for your comments. G Man confirms that the originals are cast iron and that may be the way I go bearing in mind the difficulties in machining cast iron. Will look into "Aluminium Bronze". Running standard valves so I believe the guide is reamed out to 7mm. There is always something new to discover with restoring old bikes :-)

[G-Man]

HaHa!

I knew it was a special bronze but couldn't remember the type. I remembered Hiduminium but that was the alloy that Triumph conrods are made of.

Honda used bronze guides on its genuine race bikes, as far as I know.

Here is some Aluminium Bronze on eBay. A bit oversized for the job but not as bad as the 25mm minimum for Meehanite (Cast Iron). I hate turning good material into swarf.

https://www.ebay.co.uk/i/253415297157?c ... 619&crdt=0

You should get better heat transfer and lower friction. ( neither will be measurable - it just makes you feel better).

G

Thanks for your comments. G Man confirms that the originals are cast iron and that may be the way I go bearing in mind the difficulties in machining cast iron. Will look into "Aluminium Bronze". Running standard valves so I believe the guide is reamed out to 7mm. There is always something new to discover with restoring old bikes :-)