valve timing 1951 G80

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Chris Berry
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Joined: Fri Sep 16, 2016 7:51 am
Location: QUEENSLAND AUSTRALIA

valve timing 1951 G80

Post by Chris Berry »

Hi folks, I am researching the valve timing on my 1951 G80 engine. I have downloaded a copy of the manual. The illustrations in the manual show an engine with the magneto in front of the barrel whereas mine has a rear mounted one. To me this means that the camshaft with the thread would be the exhaust one in the manual and the inlet on mine. The manual advises setting the valve timing to the No'2' on both cams. My inlet cam has no numbering just two timing marks. Using the illustrations as a guide and (my replacement cams) I have determined that my inlet cam (the threaded one on the left) is set to No '1' and the exhaust is set to No '2'. The engine seems to run OK on this with the exception of what appears to be gear backlash on the exhaust side. Can any one advise whether there is a difference in settings between a front mounted magneto and rear?

Thanks
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Rob Harknett
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Re: valve timing 1951 G80

Post by Rob Harknett »

Try looking at another manual published close to the year of your bike. But remember they used old artwork. Does this one suit your bike better?
http://archives.jampot.dk/book/Workshop ... cycles.pdf
Or maybe this 1951 Matchless Instruction book. http://archives.jampot.dk/book/Owners_m ... anuaul.pdf
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thornebt
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Location: Somerset, UK

Re: valve timing 1951 G80

Post by thornebt »

My copy of the 1955 350 / 500 heavyweight workshop manual was incorrect concerning the cam dots. It caused a lot of confusion but everything was fine when I followed Ken De Groomes 'Join the Dots' magazine article which you will find in the Help section of this forum. Cheers. Bruce.
Chris Berry
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Posts: 83
Joined: Fri Sep 16, 2016 7:51 am
Location: QUEENSLAND AUSTRALIA

Re: valve timing 1951 G80

Post by Chris Berry »

Rob Harknett wrote:Try looking at another manual published close to the year of your bike. But remember they used old artwork. Does this one suit your bike better?
http://archives.jampot.dk/book/Workshop ... cycles.pdf
Or maybe this 1951 Matchless Instruction book. http://archives.jampot.dk/book/Owners_m ... anuaul.pdf
Thanks once again Rob. Once again I've been caught out. I downloaded a 1951 AJS Manual (couldn't download a matchless one). The documents you provided me with explain all. It turns out that my current valve timing is correct for the 1951 Matchy

Chris
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