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SOHC.co.uk Forums => CB750 => Topic started by: billy192 on February 22, 2015, 06:52:40 PM

Title: valve pitting after only 2 k
Post by: billy192 on February 22, 2015, 06:52:40 PM

i am stripping my head and it has done 2000 miles since i put in new valves had them lapped but i was shocked to find the exhaust ones had lots of pitting.



(http://i1209.photobucket.com/albums/cc393/njwill1/new/Projects/CB750K6/IMG_9594_zps1isvnucc.jpg) (http://s1209.photobucket.com/user/njwill1/media/new/Projects/CB750K6/IMG_9594_zps1isvnucc.jpg.html)

what causes this pitting please?

Billy

Title: Re: valve pitting after only 2 k
Post by: Trigger on February 22, 2015, 06:59:08 PM

First question. where did you get the valves from? That is nasty

Title: Re: valve pitting after only 2 k
Post by: billy192 on February 22, 2015, 07:56:08 PM

I cant remember i get most of my stuff from DS i will have to check :-(

Title: Re: valve pitting after only 2 k
Post by: Trigger on February 22, 2015, 07:59:45 PM

Billy, can you show me a picture of the valve seats mate?

Title: Re: valve pitting after only 2 k
Post by: billy192 on February 23, 2015, 08:43:21 AM

(http://i1209.photobucket.com/albums/cc393/njwill1/new/Projects/CB750K6/IMG_9581_zpsillvezpz.jpg) (http://s1209.photobucket.com/user/njwill1/media/new/Projects/CB750K6/IMG_9581_zpsillvezpz.jpg.html)

the inlet seems fine.

(http://i1209.photobucket.com/albums/cc393/njwill1/new/Projects/CB750K6/IMG_9592_zpsummt845a.jpg) (http://s1209.photobucket.com/user/njwill1/media/new/Projects/CB750K6/IMG_9592_zpsummt845a.jpg.html)

Title: Re: valve pitting after only 2 k
Post by: Trigger on February 23, 2015, 08:54:53 AM

Did you replace all the ex valves? Is that pitting on all the ex valves ?

Title: Re: valve pitting after only 2 k
Post by: Bryanj on February 23, 2015, 05:50:01 PM

Unless the tappet clearance was too tight that is bad material mate

Title: Re: valve pitting after only 2 k
Post by: Trigger on February 23, 2015, 08:55:14 PM

Quote from: Bryanj on February 23, 2015, 05:50:01 PM

Unless the tappet clearance was too tight that is bad material mate

I have the same thoughts on this Bryan, that is why i asked: where did you get the valves from.
Still would like to know the history Billy. Did you replace all the valves? Is all the EX valves have the same pitting ?

Title: Re: valve pitting after only 2 k
Post by: billy192 on February 24, 2015, 07:04:39 PM

inlet look good no pitting at all. same make of valves. ex all the same pitting , i do think the gap may have been on the tight side.
i do tend to keep them on the tight side, yes my fault. :-[ :-[ :-[

Title: Re: valve pitting after only 2 k
Post by: Trigger on February 24, 2015, 07:29:45 PM

Quote from: billy192 on February 24, 2015, 07:04:39 PM

inlet look good no pitting at all. same make of valves. ex all the same pitting , i do think the gap may have been on the tight side.
i do tend to keep them on the tight side, yes my fault. :-[ :-[ :-[

If the gap was closed that much, then the valve would not be closing and this must of been popping. All you can do is re-cut the valve seats and re-dress the valves and try again