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Combat valves and guide fitting

Submitted by ken_normanton on Wed, 31/10/2018
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Commando

Thinking of fitting new valve guides and valves to my 750 Combat

Who in the North West(I'm in Lytham) or close to me would anyone recommend to do the work including lapping valves in

Cheers

Ken

Sent my head to RGM for new cast iron guides being fit but they need to be 2 thou over size (all of them)according to Lawrence at RGM

He says he has the inlet guides 2 thou over but dosn't have 2 thou over exhaust valves only 5 thou over size so will have to polish 3 thou off. Does anyone out there know where I can obtain a pair of 2 thou over size exhaust guides (cast iron) as this will, hopefully, save me a lump of money at £60 an hour +vat

Seen some called kibblewhite guides from America 2 thou over. Anyone heard of these guys?

Submitted by ian_cordes on Tue, 05/02/2019

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Are you hoping to source the 2 thou over guides from America, then send them to Lawrence to fit? By the time you mess around with exchange rates, carriage costs, customs duty etc it is not worth it. It will only take a few minutes to turn them down by 3 thou. 

Ian

Well Ian, Lawrence was on about polishing them down to +2 thou from 5 thou oversize not turning them down

Suppose I,m just getting a bit panicky on the total cost

What seemed a straight forward job and all that

Submitted by howard_robinson on Tue, 05/02/2019

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Sorry Ian - I thought from the text that the guides were two thou over but the valves were five thou over and you were advocating adjusting the guides .  My mistake.  As the valve seats wear it is quite common to use oversize valves to reach an unspoilt part of the seat.  I have used Kibblewhite guides in the past - expensive but good.  cheers, Howard

Submitted by david_cooper on Tue, 05/02/2019

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Would it not be easier to ream the hole to meet the guide rather than turn the guide down on a lathe? Next question might be to find out what the interference fit should be. Reaming might not be accurate enough?

Submitted by ian_cordes on Tue, 05/02/2019

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To be clear, I am sure what Ken is referring to is the fitting of 2 thou oversize valve guides, both inlet and exhaust, to which will be fitted standard sized new valves. I think in one post you omitted the word 'guide', Ken, which may be causing slight confusion.

How the omission of one word, or even one punctuation mark, can alter the meaning of a sentence. The wonders of the English language!

Dave. Maybe + 5 thou is the maximum oversize guide available. What happens the next time? Anyway, I would still think it easier to turn down the guide. I would leave that to Lawrence. He knows what he is doing!

Ian

 


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