Author Topic: Missing pilot jet  (Read 1439 times)

Offline RDfella

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Re: Missing pilot jet
« Reply #15 on: 08.03. 2023 18:53 »
So you've welded the ATD 'closed'.  If you now set the timing where it is supposed to be,  how you gonna start it? It'll kick back and maybe bust your ankle. Possibly set fire to the bike as well. It needs a little retard for starting, but not for running or, as described above, engine will lack power and overheat.
'49 B31, '49 M21, '53 DOT, '58 Flash, '62 Flash special, '00 Firestorm, Weslake sprint bike.

Offline morris

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Re: Missing pilot jet
« Reply #16 on: 08.03. 2023 19:29 »
So you've welded the ATD 'closed'.  If you now set the timing where it is supposed to be,  how you gonna start it? It'll kick back and maybe bust your ankle. Possibly set fire to the bike as well. It needs a little retard for starting, but not for running or, as described above, engine will lack power and overheat.
Hi RDfella, he has a Vape electronic ignition
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'52 BSA A 10 Plunger
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Offline muskrat

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Re: Missing pilot jet
« Reply #17 on: 08.03. 2023 20:17 »
G'day Stu.
Sounds like a combination of carb and timing. With elec ignition you can get it close but it's not until you get it running and use a degree wheel and timing light to get it spot on. Double/triple check your static timing. I'm assuming the ignition uses a wasted spark where both plugs fire at the same time but only one side fires. Where you think it's firing with valves open.
Cheers
'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
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Offline Stu

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Re: Missing pilot jet
« Reply #18 on: 09.03. 2023 00:31 »
Hi Muskrat.
Yeah, both plugs fire at the same time.I have two weeks before the plugs get here so ill keep trying to fine tune it. I keep noticing things I missed before so ill keep looking.
I'll keep spraying the carb with the cleaner.
One question, the long main jet needle fell off the half moon clamp at one time and I'm not sure I put it back on the correct slot. Where should it be? Which slot?
Zambia 1958 A10,-1961 A10, 1971 B25

Offline Stu

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Re: Missing pilot jet
« Reply #19 on: 09.03. 2023 00:33 »
While you're waiting you could set the timing up by the book....?
It's not really a "little increments" type of adjustment.
Yeah you're right, I'll keep trying to get it closer, I do have time.
Zambia 1958 A10,-1961 A10, 1971 B25

Offline Stu

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Re: Missing pilot jet
« Reply #20 on: 09.03. 2023 00:38 »
G'day Stu.
Sounds like a combination of carb and timing. With elec ignition you can get it close but it's not until you get it running and use a degree wheel and timing light to get it spot on. Double/triple check your static timing. I'm assuming the ignition uses a wasted spark where both plugs fire at the same time but only one side fires. Where you think it's firing with valves open.
Cheers
I think I had the timing set so far forward and the valves were staying open so long from the gap being so tight, it looked like it was firing on the compression side while the inlet valve was still open, almost closed. The other side inlet valve was completely closed so must have been on exhaust stroke I guess?  I had everything wrong. I figured that out and I have had some cough and farts from it today so I'm getting closer.
Zambia 1958 A10,-1961 A10, 1971 B25

Offline muskrat

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Re: Missing pilot jet
« Reply #21 on: 09.03. 2023 01:06 »
G'day Stu.
Needle position 3 from top. https://draganfly.co.uk/bsa-carburetter-jet-settings/
Cheers
'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
Australia
Muskys Plunger A7

Offline Guy Wilson

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Re: Missing pilot jet
« Reply #22 on: 09.03. 2023 07:29 »
Hey Stu! There are a few of us on this group riding A10’s a few thousands km north of you in Kenya … I do occasionally and sometimes have to buy spares from the UK, although generally I find most of what I need locally and I’d recommend not getting too fixated on getting everything from the UK.. I’ve use NGK BP6E plugs and they have been super reliable and available in Kenya .. I can’t remember when I last changed them..I just clean them on a regular basis and they keep going.
From what you’re describing and others have eluded to it, it sounds like you have a number of combined issues going on… If you have a spark and fuel in the cylinders you should get a result.. so in the absence of anything, check the static timing, tappets etc first. The easiest way is to put the bike on the centre stand, remove the plugs then rotate the rear wheel in a forward direction until you find TDC on the compression stroke.. A chop stick or something else that’s soft but won’t break down the plug hole will tell you exactly where TDC is… if your static timing is correct and the valves are set, back the rear wheel up so whatever you have in the plug hole drops by about 11mm / 1/3 of in inch (someone here will have the exact measurement) then check your mag  timing.
Its easy to the make the mistake and  time the mag after TDC rather than before..I’ve done and it ate my head for days… once you know all that is set correctly, you should get it firing.. and you can move onto sorting the carb.
The main reason my A10 runs are the guys on this forum. There’s always someone awake somewhere in the world who’s there to help. I knew very little  about my bike when I started and the generosity of information on this group is invaluable.. just keep asking and your bike will be running before you know it,
Guy

Offline Stu

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Re: Missing pilot jet
« Reply #23 on: 09.03. 2023 08:40 »
Hey Stu! There are a few of us on this group riding A10’s a few thousands km north of you in Kenya … I do occasionally and sometimes have to buy spares from the UK, although generally I find most of what I need locally and I’d recommend not getting too fixated on getting everything from the UK.. I’ve use NGK BP6E plugs and they have been super reliable and available in Kenya .. I can’t remember when I last changed them..I just clean them on a regular basis and they keep going.
From what you’re describing and others have eluded to it, it sounds like you have a number of combined issues going on… If you have a spark and fuel in the cylinders you should get a result.. so in the absence of anything, check the static timing, tappets etc first. The easiest way is to put the bike on the centre stand, remove the plugs then rotate the rear wheel in a forward direction until you find TDC on the compression stroke.. A chop stick or something else that’s soft but won’t break down the plug hole will tell you exactly where TDC is… if your static timing is correct and the valves are set, back the rear wheel up so whatever you have in the plug hole drops by about 11mm / 1/3 of in inch (someone here will have the exact measurement) then check your mag  timing.
Its easy to the make the mistake and  time the mag after TDC rather than before..I’ve done and it ate my head for days… once you know all that is set correctly, you should get it firing.. and you can move onto sorting the carb.
The main reason my A10 runs are the guys on this forum. There’s always someone awake somewhere in the world who’s there to help. I knew very little  about my bike when I started and the generosity of information on this group is invaluable.. just keep asking and your bike will be running before you know it,
Guy
Hi Guy.
That's great to hear I have compadres in Africa, they used to race these bikes in Zambia in the 70s and I bought a bunch of bikes that has been standing 20 years so I'm building mine from scratch.
I have been working on 8mm btdc to set the timing, let me try 11 as you say.
I love puzzles and this is just a big one for me.
I had and rebuilt a 65 a65 42 years ago when I was a lad in Cannock, staffs but had hundreds of guys local to me plus so many shops still selling NOS within a few miles so I'm feeling a little stranded here.
I'll keep on keeping on.
Thanks mate
Zambia 1958 A10,-1961 A10, 1971 B25

Offline Guy Wilson

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Re: Missing pilot jet
« Reply #24 on: 09.03. 2023 08:58 »
https://www.a7a10.net/forum/index.php?topic=947.msg6561#msg6561
as above...the timing setting isn't an exact science..

Offline Stu

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Re: Missing pilot jet
« Reply #25 on: 09.03. 2023 09:21 »
G'day Stu.
Needle position 3 from top. https://draganfly.co.uk/bsa-carburetter-jet-settings/
Cheers
Thanks Muskrat, let me check that.
Zambia 1958 A10,-1961 A10, 1971 B25

Offline Stu

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Re: Missing pilot jet
« Reply #26 on: 09.03. 2023 09:47 »
G'day Stu.
Needle position 3 from top. https://draganfly.co.uk/bsa-carburetter-jet-settings/
Cheers
Have I got the right needle?
Zambia 1958 A10,-1961 A10, 1971 B25

Offline Guy Wilson

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Re: Missing pilot jet
« Reply #27 on: 09.03. 2023 10:08 »
https://www.vintagebikebuilder.com/mikuni-tuning-and-jetting-guide.html

this is for a Mikuni carb although pretty universal to all carbs.. it explains pilot, slide, needle, main jet,  functions etc in relation to the engine speed and power..  the pilot and slide settings are what you need initially, then needle and main jet.. (although you said you don't have a pilot jet?)
Guy

Offline muskrat

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Re: Missing pilot jet
« Reply #28 on: 09.03. 2023 10:13 »
G'day Stu.
That looks like a concentric needle with the 3 rings at the top and for a two stroke. https://tinyurl.com/mr463m8b
What carb do you have? You should have a monobloc 389/18
Cheers
'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
Australia
Muskys Plunger A7

Offline Stu

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Re: Missing pilot jet
« Reply #29 on: 09.03. 2023 10:56 »
Check the pic, amal concentric I think. I did order this needle but obviously got the carb wrong. I don't know what I did with the old needle, I'll have to dig around for it.
Zambia 1958 A10,-1961 A10, 1971 B25