Author Topic: Misfire under load again  (Read 1379 times)

Online lawnmowerman

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Re: Misfire under load again
« Reply #15 on: 17.12. 2018 10:13 »
It's worth a try Pete - just use a piece of fluff-free white cotton cloth dampened with some switch cleaner and you can see if black carbon is coming off. I used my finger to press it on the slip ring while slowly turning the engine with the rear wheel in top gear with the plugs out but be prepared for a few shocks  *countdown*. Perhaps a piece of dowel would be safer - remember that a pencil has a graphite rod through the middle so may still give you a belt if you are touching the end.
If the rag is showing a lot of carbon then I would change the brushes.

Jim
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
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Online Klaus

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Re: Misfire under load again
« Reply #16 on: 17.12. 2018 11:33 »
Just remember me, wonderfull idle and it starts first kick. But on load,one pot misfire.
Guilty was a pick up with hair crack.

cheers Klaus


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Online RichardL

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Re: Misfire under load again
« Reply #17 on: 17.12. 2018 12:59 »
Jim,

I think ust holding down the kill button while cleaning the slip ring will avoid shocks. Good job for the wife. No wife? Tape or gentle clamp.

Richard L.
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Online Rex

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Re: Misfire under load again
« Reply #18 on: 17.12. 2018 15:36 »
Just put a small piece of cardboard or some similar non-conducting material between the points before turning it over. Just don't forget to remove it....!

Online lawnmowerman

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Re: Misfire under load again
« Reply #19 on: 17.12. 2018 16:41 »
Jim,

I think ust holding down the kill button while cleaning the slip ring will avoid shocks. Good job for the wife. No wife? Tape or gentle clamp.

Richard L.

Good idea Richard - never thought of that. I guess a test lead with a croc clip on each end could be used to earth the terminal on the end cover if working single handed. Not sure if I would trust the wife to keep the button down  *whistle*

Jim
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Online RichardL

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Re: Misfire under load again
« Reply #20 on: 17.12. 2018 19:41 »
Jim,

I think ust holding down the kill button while cleaning the slip ring will avoid shocks. Good job for the wife. No wife? Tape or gentle clamp.

Richard L.

Good idea Richard - never thought of that. I guess a test lead with a croc clip on each end could be used to earth the terminal on the end cover if working single handed. Not sure if I would trust the wife to keep the button down  *whistle*

Jim

ROTFLMAO. *lol* *lol* 
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline bsapete

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Re: Misfire under load again
« Reply #21 on: 17.12. 2018 23:58 »
I wouldn’t want to the wife to know it’s a “kill” switch! *eek*

Just when I had a brief moment this morning I warmed the bike up with a quick lap around the block then while idling I screwed the air screw in a turn which lifted the idle. (I had mistakenly used the air screw to adjust the idle down previously). I then lowered the idle back with the throttle stop screw to where I thought the idle speed should be. Took it for another ride around the block and it definitely had better power and pulled pretty well without misfire but is now pinging badly. Too lean or timing to far advanced?

Cheers
Pete
62 A10S Spitfire Scrambler
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Online Klaus

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Re: Misfire under load again
« Reply #22 on: 18.12. 2018 00:04 »
its to lean, lift the needle, this would be my first try, its much easyer.
cheers klaus


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Offline bsapete

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Re: Misfire under load again
« Reply #23 on: 18.12. 2018 03:49 »
Ok, pulled the carb off. The needle was in the top groove. Lifted it one groove so now in the 2nd from top. Cleaned the inlet filter which was a little dirty but not too bad. Screwed air screw all the way in then out
1 1/2 turns. Tickled the carb and gave it a kick. Bingo! started first kick. Went for a test ride (neighbours haven’t objected to the open pipes yet) and very much improved power and pulling pretty well. Just a little flat on initial acceleration but then she pulls hard. Perhaps just a little more fine tuning to get it spot on.
Thanks everyone for your advise. What a brilliant forum. I hope at some point I can offer some advice from my experiences too. I will continue with my magneto maintenance even though my problem seems to be fuel rather than electrical.

Cheers,
Pete
62 A10S Spitfire Scrambler
54 A7 Star Twin (sold on)
61 Jaguar E Type FHC Flat Floor
99 Jaguar XKR Coupe

Online cyclobutch

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Re: Misfire under load again
« Reply #24 on: 18.12. 2018 09:21 »
... even though my problem seems to be fuel rather than electrical.


And ain't that ever so?
Various, including ...
'58 Iron Head Flash Bitza


Online Klaus

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Re: Misfire under load again
« Reply #25 on: 18.12. 2018 09:57 »
Hi Pete,

lift the needle one groove more, and see what happend.
This engines love to run one the rich side, it is better for the internal cooling.
You have openpipes and no, or weak, reflection wave form the exhaust.

Amal chart says 1959-63 Roadrocket and Spitfire (Export) 1 5/32 bore Pilot 25 Cutaway 3 Main 290 Jet 106 needle Pos 2


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Online Rex

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Re: Misfire under load again
« Reply #26 on: 18.12. 2018 12:54 »
In another thread I recently asked for ideas for my '51 A7 that would tick-over just fine but break up badly under an accelerative load. The Amal Premier carb came "jetted for your bike", but clearly wasn't as the pilot jet needed increasing in size, the slide went from a 3 1/2 down to a 3 and the 140 main jet was increased to a 200.
That improved things a lot but still far from perfect, so the mag was stripped, the various components cleaned (including the HT spike) and one of Groily's Easy Caps fitted.

First proper run today so I couldn't go far or fast on wet roads, but the bike is transformed. Smooth and powerful.
A good blast to see if the 200 jet is correct will have to wait for drier weather, but so far, I'm very satisfied.

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Re: Misfire under load again
« Reply #27 on: 18.12. 2018 19:08 »
G'day Rex.
Most carb problems are ignition and vise versa *ex*
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Online Rex

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Re: Misfire under load again
« Reply #28 on: 18.12. 2018 21:17 »
Ah well, I was being greedy and had both. Only teething troubles and to be expected on a bike rebuild. ;)

Offline bsapete

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Re: Misfire under load again
« Reply #29 on: 19.12. 2018 07:16 »
Klaus, I’ll see how it goes with fresh 98 octane plus some booster before I lift the needle further. I sell octane booster so I can get it at the right price 😉
I contacted the PO and he told me the mag was fully rebuilt by a specialist when the bike was restored albeit 10 years ago. It’s done only a handful of miles (70) since then (just started and ridden around the block
occasionally) and I don’t think it’s ever been fettled properly. I’m enjoying this process particularly when I get positive results. Thanks to all.
62 A10S Spitfire Scrambler
54 A7 Star Twin (sold on)
61 Jaguar E Type FHC Flat Floor
99 Jaguar XKR Coupe