Starting problems

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
Member
Posts: 984
Joined: Tue Jan 15, 2008 4:18 pm
Location: SOMERSET UK

Starting problems

Postby mikeydpippin » Sat Dec 08, 2018 11:39 am

Having problems starting and getting my 57 g3 to even fire, changed points, plugs (several) timing all done, 1/2 “ Btdc
Good spark at plug, and fuel getting to plug, 140psi compression.
Now the cock up
I changed the magneto for a spare one I had, as the spark from original was poor.
Difficulty getting the auto advance unit back on and thread was not good, and the cam in points kept spinning so held the cam with grips and managed to get the thread on for the auto advance unit.
Changed the cam in the points for the original as was slightly marked.
Points opening and closing as they should with points set correctly.
I,m thinking it may be an auto advance unit sticking,
Would this cause the non firing?
Reason for working on bike was the bike was pulling back and running really rough.
Mike

Member
User avatar
Posts: 9330
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Starting problems

Postby Rob Harknett » Sat Dec 08, 2018 11:45 am

Did you jam the AR in open fully advanced position when timing ignition.? Test AR for sticking by opening by hand, it should snap back closed. Screw the first thread on, before fitting the AR on armature.
Last edited by Rob Harknett on Sat Dec 08, 2018 11:49 am, edited 1 time in total.

Member
Posts: 984
Joined: Tue Jan 15, 2008 4:18 pm
Location: SOMERSET UK

Re: Starting problems

Postby mikeydpippin » Sat Dec 08, 2018 11:45 am

Yes Rob
Mike

Member
Posts: 984
Joined: Tue Jan 15, 2008 4:18 pm
Location: SOMERSET UK

Re: Starting problems

Postby mikeydpippin » Sat Dec 08, 2018 11:54 am

Thanks Rob, may well be the problem, as it’s sticking, greased up, so will dismantle and give a good clean.
Will practice with the spare one first.👍👍
Mike

Member
User avatar
Posts: 9330
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Starting problems

Postby Rob Harknett » Sat Dec 08, 2018 12:06 pm

Well done. Cannot think what may be wrong. Since 1956 I have never had bother with an SR 1 except AR sticking. When cleaning points or any work on the mag, I always clean spring on the cover and spring/coil contact button. Removed pointed grub screw and made new contact or fitted new wire plug lead. Sometimes assembled points with insulators or fibre washers or wire wrongly. But soon discover that error when I get no spark. Pull the spring out a bit to make sure its making good contact. I clean AR when in place by flooding it with petrol / white spirit while working the unit by hand until it snaps back OK. then spray WD 40. or oil. Grease really only for the chain. If AR does stick you soon know, its a pig to start, where as if working OK will start first kick. AR must be fully closed for it to start first time. Flood to clean in place to save re timing, flood until fluid stops emerging a rust colour.

Member
Posts: 984
Joined: Tue Jan 15, 2008 4:18 pm
Location: SOMERSET UK

Re: Starting problems

Postby mikeydpippin » Sat Dec 08, 2018 12:17 pm

Thanks Rob, why is there a slot for a woodruff key on the mag shaft but no place to fit one on the AR unit?
Mike

Member
User avatar
Posts: 9330
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Starting problems

Postby Rob Harknett » Sat Dec 08, 2018 1:06 pm

mikeydpippin wrote:Thanks Rob, why is there a slot for a woodruff key on the mag shaft but no place to fit one on the AR unit?

I have never noticed a slot in the shaft, have a job to time it if there was a fixed position. Are you sure you have the correct SR1 mag? They fitted them on stationary engines also.
http://archives.jampot.dk/technical/Ele ... tions_.pdf

Member
Posts: 1831
Joined: Wed Oct 12, 2005 9:45 pm
Location: N YORKS UK

Re: Starting problems

Postby 56G80S » Sat Dec 08, 2018 1:58 pm

And tractors and marine engines and I think airplanes. I used an ex stationary engine SR1 from a friend while Tony Cooper was refurbishing the original. It really doesn't matter provided that it's got the corect taper and set for the right rotation; Tony will reset that if necessary.

It was really scruffy but worked fine, ironically even with an old style original capacitor / condensor; currently using the BrightSpark version which is great.

Kept the stationary engine SR1 as a spare for a mere £25 two or three years ago.

I don't recall (so really IKBA) but is there any possibililty that the contact breaker cam is wrongly placed, Groily will clarify.

Rob, I have a paper copy of that Lucas manual but it's in the lock up.

Johnny B

Member
Posts: 1191
Joined: Thu Jul 04, 2002 12:00 am
Location: NORMANDIE FRANCE

Re: Starting problems

Postby Groily » Sat Dec 08, 2018 2:31 pm

Such faith Johnny B! But although there is apparently a good spark at the plug in plain air, I think you've maybe hit the nail on its wossit.

It's important to set the cam position on the armature near-as-dammit per book with SRs, as there's no key. (There's probably no key because the same rotor serves in several SR models and the settings aren't quite the same on all of them . . .). So it has to be slipped on just so and then tightened onto its taper by the axial screw.

If the points open before the flip point of the rotor, there'll be no sparks as the coil won't be charged up. The problem here isn't that . . . but if it's late after the flip, then sparks will be feeble (and the later the feebler) and may not be enough to work under compression.

I'd check first off to see if you can get a cracking 1/4 inch spark from the end of a bare HT lead to earth with a flick of the wrist on the armature. You should be able to. A plug gap isn't much of a test and you'll get a spark even if things are pretty late.

The instructions for setting cam position per book are a bit of a faff involving stuffing a drill between bits of rotor and body, which you won't want to do probably. It's all in the Lucas workshop instructions, one version of which you can see here: http://www.brightsparkmagnetos.com/libr ... %20SR4.pdf
Slightly different for different versions of the SR range - hence the 'no keyway' maybe.

What you need to achieve, and you can do this with the mag on the bike with the drive gear off, is the cb starting to open just a very few degrees AFTER the flip point of the rotor. (Turning things the correct way of course!) Not more than 10° on the mag after.
You can feel the flip points easily enough with the drive off. Ideally, you want to be using the flip point (of the 2 there are per rev of the mag) which gives you a NEGATIVE spark that will jump from centre to earth electrode of the plug. You can tell which is which using the old 'flare test' - here's a useful pic using the time-honoured pencil: http://navyaviation.tpub.com/14329/Figu ... y-287.html

If the cam IS set correctly, and the sparks are really good . . . then summat else is the cause and you can happily ignore all the above!

Member
User avatar
Posts: 356
Joined: Mon May 01, 2017 6:32 pm
Location: Lancashire

Re: Starting problems

Postby spookefoote1956 » Sat Dec 08, 2018 5:37 pm

Failing that chuck a thorspark on it. Once I got mine sorted it's very reliable. Yes I know I'm going to get the magneto blah blah ............................... rant. Brace yourself Chris ........... here it comes!
हरे कृष्ण हरे कृष्ण
Hail Joe Lucas ............ Prince of Darkness!

Next

Return to G3 / Model 16

Who is online

Users browsing this forum: No registered users and 10 guests