Exhaust valve guide

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Exhaust valve guide

Postby Steve Harding » Tue Jan 28, 2020 10:07 am

Morning, 1952 Ajs 18, can anyone enlighten me on the orientation of the oil hole one the exhaust valve guide? I see the cross drilling in the head but where does the hole line up in relation to this?

Thanks

Steve

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Re: Exhaust valve guide

Postby dave16mct » Tue Jan 28, 2020 10:59 am

http://archives.jampot.dk/book/Owners_m ... Manual.pdf
On page 19 there's a drawing of the oil hole in the head. Line it up with that.
Dave.

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Re: Exhaust valve guide

Postby Steve Harding » Tue Jan 28, 2020 11:11 am

Many thanks

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Re: Exhaust valve guide

Postby Steve Harding » Thu Jan 30, 2020 12:34 pm

Hello, upon investigation, need to replace the guide. The head is possibly off a later model than the bike (1952)
The guide fitted as a shoulder, the head is recessed to accept the circlip. What is the correct valve guide part number if not a '52 head?

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Re: Exhaust valve guide

Postby 56G80S » Thu Jan 30, 2020 1:28 pm

Just as a precaution I would check the whole matter by careful measurement. The last time I did this job I found that on the replacement guide the hole in the guide had not been relieved externally and was incorrectly positioned anyway. I think the relief allows for a little error in alignment.

If you search this forum you'll find that the later heads with the circlip guides had "trays" for the hairpin springs with relief around the hole in the tray to let the circlip sit and allow the tray to be flat on the head. Not to be mixed.

From memory, the removal of those guides should be done by shifting the guide up slightly out of the head, remove the circlip and clean the guide up, heat the head and drive down into the combustion chamber. Personally, when replaceing I mark the oilway on the top of the guide and the head, heat the head and have the guide in the freezer first. I'm assuming you have a later alloy head, of course, as you seem to have suggested. Check later on in the red book.

NB the illustration shown in the link is of the inlet not exhaust guide.

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Re: Exhaust valve guide

Postby Steve Harding » Thu Jan 30, 2020 1:35 pm

Thanks for the reply. The tray is not relieved, the head is relieved around the valve guide hole (to accept the circlip)
Any ideas which year this was so I can order the right one?

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