Missing pilot jet

[Stu]

Guys, time to do the basic explaining for me, please.
I got the 61 A10 gf set up with electronic ignition, no magneto so using a battery for power. I get a good spark on both plugs but not a single beat, I'd even be happy with a misfire. I took the plugs out and kicked her over. I don't think I can smell any petrol at all from the plug holes. I stripped the carb and followed amal instructions. I had already replaced the float and needle etc with a carb kit. It looks like I bought a new style needle but I have old style jets. I'm also missing the pilot jet, must have been taken out years ago.
I have attached pictures, can you please advise what I must change. I live in Zambia so it barely gets below 20c unless mid winter so I'm not sure ill need a choke, my cable is buggered, thinking of just removing it because of other posts I've read on here.
Thanks in advance

[Stu]

After reading anything I can find, I see some carbs had the pilot taken off and replaced with a bush jet. Mine might be that type, I'll check.
One thing I just realised, the choke cable is buggered and doesn't fit into the top of the carb, meaning a load of air can pass down through the top of the carb. I forgot the carb must be air tight, dumbass me.
Still looking for any advice.
Cheers

[Triton Thrasher]

All Mk1 Concentrics have the threaded hole, but only very early ones and two-stroke versions had a jet in place there.

[muskrat]

G'day Stu.
Yes later in life of the Mk 1 concentrics the pilot jet was replaced with a bush. Take the air (pilot) screw out and look in the hole. You should see a brass bush deep inside. The hole in the jet is equivalent to a #20 pilot jet and I think about 0.016". There a real bugga to clean, soak in carb clean for a day or ten. Find someone with an ultrasonic cleaner and with the right solution it'll be done in 30 minutes. My carbs get a bath every time they come off.
As for the choke just plug the hole. Never had one on the A7 plunger down at sea level. Now up the hill 3000ft she needs a longer tickle in winter!
I'm a big fan of the new premium concentrics, better material, removable pilot, adjustable stay up float (which you can put in an old concentric), anodized slide. Not cheap but the old girl has never run better.
Cheers
TT beat me.

[KiwiGF]

After reading anything I can find, I see some carbs had the pilot taken off and replaced with a bush jet. Mine might be that type, I'll check.
One thing I just realised, the choke cable is buggered and doesn't fit into the top of the carb, meaning a load of air can pass down through the top of the carb. I forgot the carb must be air tight, dumbass me.
Still looking for any advice.
Cheers

You can see where the air and petrol travel enter the idle jet circuit from looking at the base of the carb inside the float bowl (air enters from a passage way that is on the air filter side of the carb). The two passages untersect at 90 degrees at the brass mixing chamber (as per yr pic).

As muskie says cleaning the idle jet is not easy, I use a piece of wire from an old wire brush, then remove the idle adjustment screw and insert the wire through the threaded hole and through the idle jet itself, buried deep in the car body. The “secret” is to know when the wire has actually passed through the idle jet, as opposed to stopping on the step at the entrance to the jet, from memory the wire has to travel 32mm inside.

Using a wire will unblock the jet but may leave particles of dirt still in the air passage way to the jet, which compressed air may blow out.

Be prepared to unblock the jet a few times before it stays unblocked 

The burlen web site has sime good diagrams of the idle circuit…

https://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter

PS the plug leads are the right way around?

[trevinoz]

I find it strange that people think that the top of the carburettors must be sealed to prevent air being sucked in.
Wouldn't air be sucked in around the cable end if in place?

[BSA_54A10]

I find it strange that people think that the top of the carburettors must be sealed to prevent air being sucked in.
Wouldn't air be sucked in around the cable end if in place?

When resleeving became popular, overheating from running rich became a common problem along with sooty plugs and slow acceleration.
Reaon ?
Amal compensated for the air that leaks in around the top of the slide
Those tight fitting resleeved carbs had substantially less air bleeding in so the jets became too big .

[Stu]

Ok,I found a small piece of debris in the main jet, cleaned out the carb as you all described and seems ok now as I can smell fuel from the plug hole when I kick it over with the plugs out.
Next problem....
When I put my hand over the back of the carb to choke it and kick it over,I get huge pressure blowing back through the carb.
I'm no expert but that's gotta be the inlet valves not closing properly eh?
Off with her head?

[Stu]

One more thing, I ordered a fibre timing cog but it's the same as already on the auto advance except the hole in the middle is too big so I welded the auto unit closed. Is it possible I set the timing with the auto unit open, and now have sealed it closed so the timing has gone out? When I get the pressure blowing back it doesn't seem like it's sparked, more  just like the inlet valve is stuck open and the pressure blows everything back through the carb. I've read somewhere that there will be some reverse pressure if you block the air filter, when I did this even petrol flew out of the tickler, caught me in the eye. Seems more than normal or am I wrong, again?

[Triton Thrasher]

I find it strange that people think that the top of the carburettors must be sealed to prevent air being sucked in.
Wouldn't air be sucked in around the cable end if in place?

Even though the throttle cable is never going to be hermetically sealed, I have found that a very loose fit of the outer cable in the carb top has a bad effect on low speed throttle response.

[Swarfcut]

  Presume you set the timing fully advanced with the ATD held open, and simply tacked it closed? ATD in the closed position is the setting for starting. So it should fire up and tickover OK. Any attempt to increase the revs will give the symptoms of retarded ignition, typically lack of response, stalling, lack of power and ridden like this, overheating.

 Blocking the inlet  tract means any blowback through the carb will vent as it can, the tickler being the  least restricted route to atmosphere. Probably gave the maggy a good wash as well.....

 Swarfy.

[Stu]

Ok, so I double checked the timing and valves. The spark was happening while the inlet valve was still open so I opened the valves, had them too tight, and moved the timing,I had that wrong too. It was firing too early and the valve was staying open too late. I sprayed a little wd40 down the hole and got a few cough so the timing is close or closer. Looks like I'm getting no fuel from the carb so carb cleaner and the little wire, plus a few days I guess. Thanks guys, you're help is getting me there in baby steps.

[Stu]

The timing could also be a little out, gotta be to be honest. I'll try adjusting that in little increments and see if it helps before I strip the carb.

[Stu]

I gave in and ordered new plugs and caps from U.K. Today. It's not the money, just gotta wait either two weeks for them to here. There's no way those plugs are sold in Zambia, that's the problem with being the only one doing this stuff in your country.

[Rex]

While you're waiting you could set the timing up by the book....?
It's not really a "little increments" type of adjustment.