Timing problems 18S

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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rob the rebuild
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Joined: Tue Aug 26, 2003 1:00 am
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Timing problems 18S

Post by rob the rebuild »

Had to change the timing cover gasket on my 1955 18S as it was spraying oil every where. Had gasket gooed it during the summer so knew how to get the cover off etc.
However this time when the cover came off it brought the inlet cam/gear with it. Damn and blast. So consulted manual and relined the dot on the pinion roughly with the centre line of the inlet cam hole and meshed the 2 dot with the pinion dot. Rotated the engine forward a little to check the exhaust cam was still in mesh correctly, which it was. Problem being of course the ignition timing was now out. So took an old spark plug and took out the electrode so a thin rod could pass through it. Rotated engine so both valves were shut (push rods both free to turn etc). Put new TDC indicator in plug hole rocked back wheel to and fro to find TDC and then as per the book marked another line 1/2" above it. Then rotated wheel back until new line was level with top of old plug housing. Put advance lever to fully advanced and with the aid of a fag paper found where the points just started to open by turning points clockwise from points side (anti clockwise from sprocket end as per the book).
Engine will not fire, but had a few loud back fires.
Am I missing something somewhere? or is there a hidden trick?
itma
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Timing problems 18S

Post by itma »

you have timed it on the wrong stroke.
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rob the rebuild
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Joined: Tue Aug 26, 2003 1:00 am
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Timing problems 18S

Post by rob the rebuild »

So how do you know what stroke to time it on? or is it just hit and miss?
Which in my case must be more miss than hit.
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Chazzyb
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Timing problems 18S

Post by Chazzyb »

quote:
So how do you know what stroke to time it on?

I get mine onto the compression stroke using the K/S, then put the 'box into top, whip the plug out and turn forwards using the rear wheel until TDC.
Charles
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rob the rebuild
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Joined: Tue Aug 26, 2003 1:00 am
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Timing problems 18S

Post by rob the rebuild »

Deep joy. Bike is now fully timed and running better than before. This was my first attempt at timing the bike as I have not had to do it in the 3 years that I have had it. So how did I get myself out of this pickle. Well went back to basics, and did the same thing brought it up to the compression point (whilst using son to watch valve rockers), whipped the plug out and in with the home made gauge and lordy lordy 180 degrees out after moving the magneto sprocket. Fired up after about 4 kicks (just very cold). The other good news is that the timing cover oil leak has been cured as well.
So thanks for those that have read and commented, I am now no longer a timing virgin (valve or ignition).
So baring snow drifts and mega icy roads should now be able to make the Wickham meet on Boxing Day (that will be another first).
itma
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Timing problems 18S

Post by itma »

Ist principle of the infernal combustion engine, suck, squeeze ,bang, blow.
After aligning the marks on the cam the engine has to be rotated thru` 360 degs to bring the cams to ignition position,peculiar to AMC I think.
10/10 for working it out on your own Practice of suck it and see is an excellent teacher, you`ll remember next time
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