Slow G3

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
MikeC
Posts: 12
Joined: Wed Aug 19, 2020 12:59 pm
Location: Wiltshire UK

Slow G3

Post by MikeC »

Hi all
I have a 1958 G3LS
I've only had her for a couple of weeks, and we are getting to know each other.
I know the performance is not earth shattering, but 45mph on the flat and level is not great.
Climbing a moderate hill means dropping down to 2nd and only 20mph
I thought that perhaps the automatic advance/retard mechanism is stuck.
Is there any easy way of checking this?
Any other pointers would be gratefully received.

Cheers
Mike
Mike Croudson
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Slow G3

Post by SPRIDDLER »

No that's no good. Presumably it has always been like that?
Does it rev freely when in neutral?
Assuming that the ignition is correctly timed you can rotate the points plate by hand to check that it operates freely and the bobweights move outwards against their springs. The A/R unit is well known to stick.
You can also check the points gap as over time the points tend to develop pips which reduces the gap which will retard the ignition timing.
Also check that the main jet (assuming it has the right one) isn't blocked/obstructed.
Is the engine note 'flat'? Does the engine get very hot and/or is the zorst pipe blueing badly at the exit from the cyl head? Both are indications of retarded timing.
As an aside, a common mistake with a new bike is to ride with the choke on. The choke is off when the cable is pulled tight by the h/bar lever.

If you don't have them the manuals are available under 'Books' in the link below:

http://archives.jampot.dk/
Last edited by SPRIDDLER on Sun Sep 11, 2022 10:05 am, edited 1 time in total.
'There is a tide in the affairs of men
Which taken at the flood............'
User avatar
clive
Member
Posts: 5657
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: Slow G3

Post by clive »

You are right that you should get better performance and it does sound like a retarded engine. The auto advance can be checked with the engine off. Take the timing cover off and turn the advance b hand. It should snap back when released. If it does not the cause can be wear in the stud that the weights hinge on, weak springs or the chain being too tight. So worth slackening the chain to see if it improves things. Also if it stood for a while before you got it try giving the mechanism a thorough squirt with WD 40 to see if it eases up.
clive
if it ain't broke don't fix
MikeC
Posts: 12
Joined: Wed Aug 19, 2020 12:59 pm
Location: Wiltshire UK

Re: Slow G3

Post by MikeC »

Thank you for your repies.
A few things to check.
Thanks for you time and input.
Cheers
Mike
Mike Croudson
User avatar
jackstringer
Member
Posts: 321
Joined: Thu Oct 08, 2009 6:09 pm
Location: Somerset UK
Contact:

Re: Slow G3

Post by jackstringer »

For the fun of it it's worth giving the carb a bit of a clean. Check there is plenty of flow from the tank while you are at it.

If you can get to a local group meet you might find it worth letting another member have a quick go on yours or vice a verse versa as its handy way to judge if it's just you or your bike that has a issue.

Not that it's common but check the sprockets.
User avatar
Pharisee
Member
Posts: 1126
Joined: Tue Mar 15, 2016 8:51 pm
Location: Lincolnshire UK
Contact:

Re: Slow G3

Post by Pharisee »

That's 10-15mph slower than I cruise my '54 G3/LS and I would still have a little in hand.
Fair enough, mine has a manual A/R but you do seem to have a problem. As has already been suggested, ignition timing and carburation should be checked. Do you have plenty of compression or can your machine be started easily without using the exhaust valve lifter?
I'm from the Fens.... Gimme six.
MikeC
Posts: 12
Joined: Wed Aug 19, 2020 12:59 pm
Location: Wiltshire UK

Re: Slow G3

Post by MikeC »

Hmmm, lots to think about.
Compression seems OK, I can start it without the valve lifter, but it takes some effort.
It's obvious that the bike has been rebuilt, but has been standing for some time.
I put new fuel into the tank, but still a lot of brown sludge came out when I tickled the carb.
Next job, clean carb and flush out the tank.
When I look at the points, and turn over the engine, only the cam moves, and opens the points.
I would have expected to be able to rotate the A/R bobweights by hand, but I can't.
I'll take some photos later today, and post here.
Cheers
Mike
Mike Croudson
MikeC
Posts: 12
Joined: Wed Aug 19, 2020 12:59 pm
Location: Wiltshire UK

Re: Slow G3

Post by MikeC »

Hi all
I have now taken on board your comments and suggestions.
I've cleaned the carb, seems OK.
I've also dismantled the timing cover and points plate.
The issue I have (I think) is that the A/R weights are very loose.
I can move them a few degrees before the springs take up the slack.
Is this right?
Can I move the springs to the second hole on the mounting plates, so making them a but tighter?
Please see the attached photos
Thanks for any suggestions
You do not have the required permissions to view the files attached to this post.
Mike Croudson
User avatar
1608
Member
Posts: 2493
Joined: Mon Oct 05, 2009 1:00 am
Location: ESSEX UK

Re: Slow G3

Post by 1608 »

I wouldn,t move the spring to the 2nd hole as this will probably cause the spring to tighten and prevent the timing from advancing as it should with engine speed. This would make the bike less responsive and slower. I don,t think the a/r is the problem. It sounds more like carburation.
g80csp11
Member
Posts: 1567
Joined: Mon Jan 01, 1990 12:00 am
Location: WEST SUSSEX UK

Re: Slow G3

Post by g80csp11 »

just makes sure the timing is set with the bob weights wedged fully advanced , it should not take much effort to moved and should return easily under spring tension
Locked