1951 G80s timing/points/fuel?

[Old Thumper]

I am looking for any advice with regard to my 1951 G80s

Having got my 16MS out of the shed and all prepped for the IJR my attentions turned to my 1951G80s.
She was given fresh oil and fuel and she fired up and sat ticking over quite happily. My plan was to use the bike for a couple of runs to work (@30mins) as a shakedown as I had with the AJS. Next morning the bike fired up without any major issues abut before I had even got out of the street it was stuttering, popping and probably woke a large proportion of the village up with a couple of very loud backfires. Thankfully I managed to limp it back home into the garage where it currently sits.



My first assumption was that the timing must have slipped so yesterday evening set about resetting the timing (1/2" advance from TDC with the manual advance/retard set to fully advanced) and....nothing! :
Time to re-check myself (aka - do it all again) and this time after a few kicks the bike springs into life with a very healthy and smooth roar. "Super" thinks I.."I have cracked it". However having stopped the bike it will no longer start again - not even trying
I have checked and appear to be getting a healthy spark so it would indicate the Mag/points are working ok. The Mag was rewound when my Dad and I first started putting the bike together and whilst that is a few years ago now it has not been used much in between.
I am currently part way through a full strip, clean reset of the timing/points etc but was just wondering if anyone out there had already had something similar and could help point me in the right direction?

If this approach doesn't work I will move onto a carb strip/rebuild to rule out any potential fuel delivery issue. However in the meantime does anyone from the collective mind have any suggestions or pointers? Is there any way to test the Mag in situ with a multimeter?

[ajscomboman]

Had the same issue with the wifes 350 LCT and it was the plug, it'd fire outside resting on the rocker box. It'd fire once when inserted then nothing! New plug and all was fine and has been since. No reason for the plug to fail just did.

[Matchbox Kid]

https://www.matchlessclueless.com/elect ... as-dynamo/ will give you the dynamo test with it in situ, also a useful site for some testing in general.
My only other suggestion is E10 fuel, it doesn't like being stood for any length of time and goes stale very quickly.
Good luck
Paul

[clive]

Recheck timing? I know you have just done it but could it have slipped again? Often mags playing up suggests condenser as the problem but a healthy spark suggests not perhaps. Cannot help with multimeter test data but Groily may be able to help. If he does not pick this thread up try a private message to him. However the suggestions of fuel and spark plug make sense. I have trouble with my G80 when using up a bit of old fuel, misfiring at speed. Took the trap under main jet on the monobloc carb and there was water there.

[Old Thumper]

Thanks for the inputs.

The plug is quite new - but as you say they can break down without reason and it is an easy check, so I will bang a new one in and see how that goes.

The tank was drained over the winter so the fuel is new, though I guess there could potentially be residue or whatever in the carb - hence a strip/clean on the to do list.

I am currently doing a full deep strip and clean of all the timing components to double check the settings and to try and minimize any potential for future slippage.

Hopefully I will feedback with positive news. If not I will probably still bring it to the IJR for the gathered experts to weave their magic on it

[SPRIDDLER]

https://www.matchlessclueless.com/elect ... as-dynamo/ will give you the dynamo test with it in situ,

It's the mag that's under suspicion.

I'd try a couple of quick and dirty checks.....

A new or an alternative plug.

Closing the plug gap to say 10 or 12 thou may help if the mag is getting weak, Also try using less retard when starting as the spark is strongest at full advance and weakens as the ignition is retarded. (Keep yer knee bent ).

I find that when the bike is left unused the Pilot jet becomes clogged - especially since the addition of ethanol. If it still has the pre-Monobloc carb it's best to remove the carb to clean all jets but with the Monobloc you can just remove the Pilot jet cover and the jet to ensure that the tiny holes in the jet are clear because there are several and they really are tiny.

[Old Thumper]

Well I just wanted to say thank you to everyone for their ideas .

Tonight was spent stripping, cleaning and blasting through the carb with my little compressor, cleaning and resting the points, re-timing the bike again from scratch and treating it to a new spark plug as well. The result......she fired up first kick and I have just had a very pleasant half an hour pottering around the local country lanes before the sun went down...without her missing a beat .



fingers crossed for a couple of uneventful runs to work then next stop will be the IJR

[century]

nice looking machine ,well done mate

[clive]

Good news, well done

[Matchbox Kid]

Ooops... Mag not dynamo, must learn to read properly... but that site is a mine of useful stuff anyway so no harm in posting the link.
Glad you got it sorted, looks a nice bike
Paul