55 G9

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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55 G9

Postby Oggers » Tue Jun 18, 2019 8:45 am

Chaps

A very pleasant bimble around upper Deeside on Saturday revealed a dry bike with just a couple of drops of oil when back in the garage. My thanks to all. One thing I noticed is that on pulling the adv/ret lever further towards the bike - ostensibly retarding a tad further - the bike did seem to run slightly better in general on the flat and up hills. Is it practice that once a reasonable position for the adv/ret has been found, then best to leave it alone rather than fiddle about retarding a tad further uphill? I guess this means it may not be as advanced as it perhaps ought be on the flat - but does this matter?

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Re: 55 G9

Postby SPRIDDLER » Tue Jun 18, 2019 10:22 am

It's a possibility that the timing was set too advanced to start with............ :?
However, your Owners Manual has this to say about retarding on hills:
G9 retarding (640x168).jpg

Owners Manual:
http://archives.jampot.dk/book/Owners_m ... Manual.pdf

'Old timers' would habitually retard the timing when running slowly or up long inclines.

Too much retard at cruising speeds can cause overheating and reduce top speed and the 'livelieness' of the engine but I guess you'll need to assess that by trial and error. Whilst having a high speed run (if you fancy doing that) you could advance the timing and see if acceleration/top speed improves.
The mag physics dictate that the fattest/strongest spark occurs at the fully advanced position.
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Re: 55 G9

Postby Oggers » Tue Jun 18, 2019 10:39 am

Spriddler

It is indeed possible that the timing was set too far advanced or that the adv/ret cable is not adjusted properly. Either way, the position the lever is in now seems fine. If I knock it forward - advance it, but not necessarily to the correct advance! - the engine seems less "meaty" and responsive for want of better words, but it is a fine line.

I think a little trial and error when riding as you suggest is called for.

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Re: 55 G9

Postby SPRIDDLER » Tue Jun 18, 2019 11:21 am

I've never ridden a twin so can only guess that it's more advantageous to retard a slow revving longstroke single rather than a twin on long inclines.
I have occasionally retarded the timing when going uphill or into a strong headwind loaded with camping gear on my 350 and travelling at a speed a bit too great to be comfortable in a lower gear. I do though subconsciously check that the A/R lever hasn't crept towards the retard position (slack wire on mine) - similar to my habitual checks these days for full advance of my fly zip when out and about :roll:
I poke badgers with spoons.

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