My sons "new" AJS Model 20

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Re: My sons "new" AJS Model 20

Postby G15 Roy » Wed Jul 19, 2017 2:03 pm

The Best thing you can do is not alter anything and take photos of both levers and post them here and wait for the advice.
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Re: My sons "new" AJS Model 20

Postby Rob Harknett » Wed Jul 19, 2017 2:53 pm

Daveinater wrote:Hi guys,
Yes, sorry, my description wasn't so good there. I will have to double check the lever positions. I think he set the choke lever in the OFF position and tightened it there, saying we wouldn't need it. As for the timing lever, yes this has one as well, and we haven't messed with it much but it is in the "fully forward" (towards the front of the bike) position. I think he said if we pull the lever, we would advance the timing, so that would mean it's been fully retarded. (I may have that basackwards. Old age does that to a guy. Lol)

I will double check these when I get home.

As for the mixture, sound like we need to re-jet the carb. SIGH. Probably not something I'd try myself. Is that a science and are the jets readily available?

Sounds like you did have the lever fully retarded, the bike will lack power / speed, run hot etc. Retard the lever upon starting, fully advanced the bike will usually kick back. You will discover the best retard amount suits the bike. When warmed up, fully advance the lever, revs will pick up more when you do this. This warm up depends how cold it is. With a warm engine you will need no choke, just a retard the A/R lever. Start the bike, gradually advance the lever fully, then off you go. If the bike is not fully warmed up as you ride off, the engine may stall very easily when you close the throttle.
Riding the machine retarded could have been your only problem. This is a very basic, starting the engine procedure, that should be seen in the instruction book.
Perhaps overlooked by yourself, also us in trying to resolve your problem. So as you have been advised, don't do anything, only do one thing at a time, ask first etc. Perhaps the latter is best, so we get a little more history and between us all come to a conclusion what you need to try or do.

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Re: My sons "new" AJS Model 20

Postby leswaller » Wed Jul 19, 2017 3:05 pm

If you are running a magneto on your model 20 the chances are that the ignition is fully advanced with the lever forwards, i.e. slack cable. This is the way it is on my model 20.
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Re: My sons "new" AJS Model 20

Postby SPRIDDLER » Wed Jul 19, 2017 3:43 pm

Explanation of the controls settings and starting instructions are in the Owners Manual - link below to Christians Archive (to which I referred you on the first page of this topic, although I expect with all the info coming at you you've going around with your head in the clouds ;) ).
Ignore the fact that it's for a '55 Matchless G9 as it's all the same as for your '56 Ajay Model 20. There is an Owners Manual for your Ajay but it is a generic one covering ALL '56 Ajay twins so by using the Matchless one will it save you having to plough through all the (much of it irrelevant) stuff referring to the other models of Ajay twins.
See pages 6,7,8 &9 et sub.

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

(For some reason it's sometimes necessary to close the link and then re-open it to get it to open full size :roll: ).
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Re: My sons "new" AJS Model 20

Postby Daveinater » Wed Jul 19, 2017 6:47 pm

Lol you guys are awesome.

The photo of the "store"? I know the place well. I most often visit that "Creek" when I say something "funny" to my wife of 30 years, only to realize it wasn't...so...funny. I then wish for a paddle as the creek carries me downstream (and over very high falls). Eventually I land on shore and think I'm smarter for it. Til I do it again. (I married out of my league so I'm just happy to still have a boat at this point).

I will study the guide. (You'd think that I would have done that, given my line of work). Honestly, the British bike mechanic gave us a "ground school" of sorts and basically said "leave this choke alone and this lever advances and retards the ignition. Really don't mess with it because it changes where in the cycle it will spark and can really mess things up if you don't know what you're doing." Yes a sharp guy so that's about as much as we know, and I'm probably even misquoting him---my son and I were trying to digest it all as best as possible.

I will take photos of the levers asap. I'm guessing that will clear a lot of things up!

Janet! Sage advice. I think a very methodical approach is the way to go. I will heed your advice.

You guys are great. Sometimes these forums can be treacherous waters for newbies because we tend to ask "the same #%€&@!! questions over again" and it can be irritating. Y'all have been so gracious and helpful. Thanks so much. This has been hard on my son because he's home for only 1 more month before heading back to college and he's been unable to ride "Pop's bike".
Last edited by Daveinater on Wed Jul 19, 2017 7:50 pm, edited 1 time in total.

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Re: My sons "new" AJS Model 20

Postby SPRIDDLER » Wed Jul 19, 2017 7:47 pm

Daveinater wrote:the British bike mechanic gave us a "ground school" of sorts and basically said "leave this choke alone and this lever advances and retards the ignition. Really don't mess with it because it changes where in the cycle it will spark and can really mess things up if you don't know what you're doing."

From what you've said in your various posts he sounds reassuringly like he's on the ball with old bikes.

Sometimes these forums can be treacherous waters for newbies because we tend to ask "the same #%€&@!! questions over again"

That's how I gained specific knowledge to complement an engineering apprenticeship; much of it from some who are no longer with us and I'm just pleased to be able to pass it on.
Even though almost all information can be found on the internet, information isn't the same thing as knowledge.
It's great to hear from a 'new' owner, and satisfying trying to help, (especially on Day 6 of being trapped at home with 'Manflu' :headbang: ).
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Re: My sons "new" AJS Model 20

Postby shifter » Wed Jul 19, 2017 8:07 pm

The A/R lever on my model 20 1951 spec is on the left (clutch side)of the bars lever forward full advance, the air valve (choke) is on the right with the lever facing towards the rear of the bike, to start my bike from cold I bring the A/R lever back about a 3rd tickle the carb and leave the choke as it is unless its minus 0 or below kick her over to start after a few seconds push the A/R lever forward and off she goes
Last edited by shifter on Wed Jul 19, 2017 8:53 pm, edited 2 times in total.
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Re: My sons "new" AJS Model 20

Postby Daveinater » Wed Jul 19, 2017 8:31 pm

Rob Harknett wrote:Sounds like you did have the lever fully retarded, the bike will lack power / speed, run hot etc. Retard the lever upon starting, fully advanced the bike will usually kick back. You will discover the best retard amount suits the bike. When warmed up, fully advance the lever, revs will pick up more when you do this. This warm up depends how cold it is. With a warm engine you will need no choke, just a retard the A/R lever. Start the bike, gradually advance the lever fully, then off you go. If the bike is not fully warmed up as you ride off, the engine may stall very easily when you close the throttle.


This from Rob, plus the photos from you, Shifter, has really helped. My son is going to send me photos of where our timing and choke levers are. We haven't moved either....at all.

I am pretty sure the timing lever is in the fully advanced setting (not pulled rearward at all) and the choke is also not pulled. Based on Shifter's photo, I'm wondering if we are driving it fully choked?

Rob, your description of how it can stall easily if not fully warmed up is spot on. That's exactly what it's doing. It always stalls after the first stop once we get it running. Thankfully we live in a small town because I've had to push it off the road more than once!

I read the starting instructions from the link provided. We haven't been retarding the timing, nor have we been moving the choke lever.

I'll post photos of both levers shortly. Thanks again all!

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Re: My sons "new" AJS Model 20

Postby Rob Harknett » Wed Jul 19, 2017 9:31 pm

Daveinater wrote:
Rob Harknett wrote:Sounds like you did have the lever fully retarded, the bike will lack power / speed, run hot etc. Retard the lever upon starting, fully advanced the bike will usually kick back. You will discover the best retard amount suits the bike. When warmed up, fully advance the lever, revs will pick up more when you do this. This warm up depends how cold it is. With a warm engine you will need no choke, just a retard the A/R lever. Start the bike, gradually advance the lever fully, then off you go. If the bike is not fully warmed up as you ride off, the engine may stall very easily when you close the throttle.


This from Rob, plus the photos from you, Shifter, has really helped. My son is going to send me photos of where our timing and choke levers are. We haven't moved either....at all.

I am pretty sure the timing lever is in the fully advanced setting (not pulled rearward at all) and the choke is also not pulled. Based on Shifter's photo, I'm wondering if we are driving it fully choked?

Rob, your description of how it can stall easily if not fully warmed up is spot on. That's exactly what it's doing. It always stalls after the first stop once we get it running. Thankfully we live in a small town because I've had to push it off the road more than once!

I read the starting instructions from the link provided. We haven't been retarding the timing, nor have we been moving the choke lever.

I'll post photos of both levers shortly. Thanks again all!

Could be you are running fully choked , looking at the black plug. You can go far wrong just changing lever positions. Both need to be correct as advised. Setting of both upon starting may vary for best results. If the bike still does not perform as it should, take next steps one at a time as advised, let us here conclude first what is most likely to be the main problem.

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Re: My sons "new" AJS Model 20

Postby Daveinater » Wed Jul 19, 2017 11:01 pm

Here are some photos.

Well my memory didn't serve me well. I could have sworn the choke lever was fully forward but it's not. It appears to be in the "un-choked" position. The timing lever is full advanced and hasn't been moved at all.

Given the black, sooty plugs.....any suggestions as to the next step?

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