Exhaust Valve Guides

Information relating to the Matchless G11 or AJS Model 30 600cc twin
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Exhaust Valve Guides

Postby melsajs » Sun Apr 05, 2020 11:16 am

I need to renew the exhaust valve guides on my Matchless G11 1957.

I've never undertaken this before so am after a few pointers. I know about heating up the head & freezing the new guides before putting them but I'm uncertain as to which way to drift the old ones out. I've been told to (when hot) using a suitable drift force the guide into the rockerbox area enough to remove the circlip. Then drift it out through the exhaust port (drift on rocker box end of the guide). Is this correct

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Re: Exhaust Valve Guides

Postby cbranni » Sun Apr 05, 2020 1:59 pm

In a nutshell yes, (unless your guides have no build up of carbon then you can knock them out in the rocker box direction), make sure the location pin on your drift is decent fit in the guide and is at least an inch long, and there is an undercut at the end of the location diameter and guide diameter, if there is a radius you can damage the new guide.

You can locally warm the head in the area of the guide or put in the oven at 150ish then knock back the guide to remove the clip then reverse and drive the guide out towards the combustion chamber. Putting in new ones is quite simple, warm the head, put the NEW clip onto the guide, line up the oil hole (very important) and knock it in until it's home.

You don't gain a lot by freezing the guide.

Colin
only dead fish go with the flow

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Re: Exhaust Valve Guides

Postby melsajs » Sun Apr 05, 2020 3:16 pm

That's all noted particularly about lining up the oil hole and the drift. Thanks for the quick response.

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Re: Exhaust Valve Guides

Postby Stan Palmer » Sun Apr 05, 2020 7:02 pm

Been my opinion for some time now that freezing a guide or bearing actually has an adverse effect. It doesn’t reduce the size of the frozen item by much, but does draw a lot of heat very quickly from the heated component, effectively making the fit tighter rather than looser. Maybe there’s a locked down physicist out there that could prove or disprove !
Stan

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Re: Exhaust Valve Guides

Postby 56G80S » Sun Apr 05, 2020 7:35 pm

Stan

Perhaps it's tied to how fast you move!

Do you want some of this klingerette or not?

Johnny B

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Re: Exhaust Valve Guides

Postby melsajs » Sun Apr 05, 2020 9:47 pm

Stan - Like the logic - i am not going to bother cooling the guides down.

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Re: Exhaust Valve Guides

Postby Mick D » Mon Apr 06, 2020 6:27 am

Stan Palmer wrote:Been my opinion for some time now that freezing a guide or bearing actually has an adverse effect.


Hi

I don't think this is true - anything that increases/maintains the temperature differential between the two items is beneficial, in this case for example, freezing the insertion tool.

Yes the head will warm the guide but the colder the guide is the longer it will take to warm up to a certain temperature.

I always freeze/heat interference fit components. The items being frozen are put into zip lock polythene bags and have lubrication/sealer applied before freezing if possible. Often bearings will drop into place with no force.

Wearing gloves slows the transfer of heat from your hands to the frozen parts and allows you to handle housings heated to suitable temperatures.

Regards Mick

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Re: Exhaust Valve Guides

Postby Stan Palmer » Mon Apr 06, 2020 7:48 am

Johnny, I must have missed the offer of klingerette. Is this the thick gasket with a plastic coating ? I will measure how much I need and If the offer is still open, yes I would like some. Pay pal ok ?
Stan

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Re: Exhaust Valve Guides

Postby melsajs » Mon Apr 06, 2020 8:42 am

Mick, On reflection i think I will do what you suggest - it seems to be the most common approach.
My G11 has been in my garage for about 10 years untouched/unused I bought it in 1999 and did start a restoration including rebore/powder coating the frame etc . I was just going to sell it in its current state but decided now might be the time to finish it - thanks again for your help

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Re: Exhaust Valve Guides

Postby 56G80S » Mon Apr 06, 2020 12:44 pm

Stan

Sent a PM before I read this post. It's free, particularly after your offer of loan of a trailer! It doesn't have plastic coating, but Ive used it as the seal for the inspection cap and it does the trick.

Johnny B

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