Im Stumped!!

Information relating to the Matchless G9 or AJS Model 20 500cc twin
Member
User avatar
Posts: 18
Joined: Sat Mar 16, 2019 8:48 pm
Location: Christchurch New Zealand

Re: Im Stumped!!

Postby NZMatchless » Tue Jul 02, 2019 1:02 am

Rob Harknett wrote:Try a new recommended type plug instead of changing them round. There maybe a slight difference on the dodgy cylinder the old used plugs don't like


Ive got brand new Champion N5C tried swapping them around still the same
Ride New Zealand - Live the Dream

Member
User avatar
Posts: 18
Joined: Sat Mar 16, 2019 8:48 pm
Location: Christchurch New Zealand

Re: Im Stumped!!

Postby NZMatchless » Tue Jul 02, 2019 1:05 am

MalcW wrote:Just out of interest, have you tried removing the RH plug before starting from cold, to see if it's actually sparking at that point? As has been pointed out, changing the plugs completely, rather than swapping, could be worth a try. I have recently fitted Champion N5C plugs (previously NGK B8ES) and it's made a big difference. Have you tried swapping the HT cable and plug caps from side to side?
Also, have you tried a compression test? If you don't have a compression tester immediately to hand, does the compression feel similar on both cylinders when kicking it over? It does have the feel of a mechanical issue rather than electrical - sticking valve or piston rings for example.

Malc


Just checked compression on a cold engine, 110 on each cylinder, seems pretty good,good compression indicates good rings not sure about sticking valve though although its a reconditioned Magneto Ill try swapping plug leads,
Ride New Zealand - Live the Dream

Member
Posts: 368
Joined: Tue Oct 24, 2017 11:05 am
Location: DEVON UK

Re: Im Stumped!!

Postby MalcW » Tue Jul 02, 2019 8:40 am

If you can, when you swap the leads, swap the pickups as well; be careful though, it's hard to remove the pickup nearest to the barrels with the magneto still in place. I only suggest that because it's not unknown for the carbon pickups or their holders to have issues.

Malc

Member
User avatar
Posts: 2032
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Im Stumped!!

Postby dave16mct » Tue Jul 02, 2019 10:08 am

Have you checked the points gap on each cylinder. The ring cam wears and you can get very different settings which have to balanced out between the two(or a new/reground cam). Not sure if it would cause these symtoms but something else to check.
Dave.

Member
User avatar
Posts: 18
Joined: Sat Mar 16, 2019 8:48 pm
Location: Christchurch New Zealand

Re: Im Stumped!!

Postby NZMatchless » Tue Jul 02, 2019 9:32 pm

dave16mct wrote:Have you checked the points gap on each cylinder. The ring cam wears and you can get very different settings which have to balanced out between the two(or a new/reground cam). Not sure if it would cause these symtoms but something else to check.
Dave.


Worth a look, although It does have a new cam ring as the original was so worn,
Ride New Zealand - Live the Dream

Member
User avatar
Posts: 18
Joined: Sat Mar 16, 2019 8:48 pm
Location: Christchurch New Zealand

Re: Im Stumped!!

Postby NZMatchless » Thu Jul 04, 2019 4:16 am

Well I think Ive sussed it!!, it was the timing!, I thought I'd timed it correctly but the cogged wheel must have moved when I tightened it and it was to retarted!, tried again today and this time I think ive got it right (3 attempts), there must be an easier way!!. it still fires up on one cylinder but only for a couple of beats then onto two cylinders, it still may be slightly out but thats a project for another day. Thanks for all your help.

Mike
;)
Ride New Zealand - Live the Dream

Member
Posts: 368
Joined: Tue Oct 24, 2017 11:05 am
Location: DEVON UK

Re: Im Stumped!!

Postby MalcW » Thu Jul 04, 2019 8:43 am

Well done, that's a good result. I've had the same problem in the past. I've found that it helps (but isn't foolproof) to put the magneto gear into place, then use a suitable sized socket and a rubber mallet to tap it onto the shaft before tightening the nut.

Malc

Member
Posts: 2192
Joined: Wed Oct 12, 2005 9:45 pm
Location: N YORKS UK

Re: Im Stumped!!

Postby 56G80S » Thu Jul 04, 2019 12:52 pm

That works on singles too!

Johnny B

Member
User avatar
Posts: 18
Joined: Sat Mar 16, 2019 8:48 pm
Location: Christchurch New Zealand

Re: Im Stumped!!

Postby NZMatchless » Thu Jul 18, 2019 4:26 am

Finally solved the starting up on one cylinder problem, after numerous cups of tea, and retiming half a dozen times again!, I decided it must be a plug problem, so, I had the plug gap set at 18 thou, and clearly not working, so I reduced the plug gap down, 16, 14 and finally 12 thou and ......Voila!, it started, first kick, both cylinders!, I couldnt beleive it, so took it for a ride and it run splendidly. Tried again the next day and the day after that with the engine cold, its winter in New Zealand, and still strarts on 2. Im a happy soldier!!

Mike
Ride New Zealand - Live the Dream

Member
User avatar
Posts: 2851
Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: Im Stumped!!

Postby ajscomboman » Thu Jul 18, 2019 6:26 am

Not wishing to put a damper on your spirits, if you've had to reduce the plug gap that small I'd be slightly concerned about the quality of the mag rebuild. A good mag should easily fire a plug set at 25 thou, factory setting for a mag is 22 and your one didn't like firing even at 18. Run it as it is but it really doesn't sound as though it's in tip top condition.

PreviousNext

Return to G9 / AJS Model 20

Who is online

Users browsing this forum: No registered users and 4 guests