53 plunger 626 carb jet sizes

[Leyland lad]

Hi all,

Sorry for my lack of understanding but I have a 626 carb originally fitted with a 240 main jet and 106 pilot.
Started well but plugs sooted up within 4 miles.
I changed the main to a 170 and replaced the needle as advised by the burley rep, bike starts fine but plugs are still sootier than a sooty thing!
The bike does start to misfire after 4 miles but I assume that is because the plugs are sooted up.
Can anyone confirm the jet settings and/or advise any way forward
Many thanks
Ian

[Triton Thrasher]

Have you experimented with needle clip position?

Other than that, read and follow the widely-published Amal tuning procedure.

[Leyland lad]

Hi, yes I tried adjusting the needle position.
I’ll study the Amal tuning guide (found on Hitchcocks website) and see how that goes
Cheers

[Swarfcut]

 Just a thought. You are turning off the choke? Easy mistake to make, slackening the choke cable lever  lowers the choke into the airstream, and applying the lever turns the choke off. The complete opposite of conventional choke operation for those used to cars before the advent of fuel injection.
  626 type, so called Concentric Carb is the wrong one. It should be a 276 with remote float bowl, and the published data for the model year applies to these earlier carbs.

 Swarfy.

[Leyland lad]

Yes I’ve ridden without choke and no difference. Can’t be anything serious just need to try tuning again.
I’ve just got the bike and the 626 was already fitted but I understand it’s ‘tunable’’ and give it a try before I invest in a 276.
I’ll let you know how I get on
Thanks for the info
Ian

[BSA_54A10]

What plugs are you running ?
I run most of my bikes now days on NGK's that are 1 to 2 grades hotter
The best textbook match are B 8 & I run BP 6 around town & BP 7's if I will be doing a long ( over 100 mile ) run

[Leyland lad]

Hi,
Yes I’m also running NGK plugs. Progress made, plugs are now the correct colour after retune.
Tick over is also nice now, just need to sort out a bit of splutter on acceleration.
Cheers
Ian

[morris]

Hi,
Yes I’m also running NGK plugs. Progress made, plugs are now the correct colour after retune.
Tick over is also nice now, just need to sort out a bit of splutter on acceleration.
Cheers
Ian

Had the same issue when colourtuning mine. Nice blue flame both at tickover and full throttle but spluttering on acceleration. Closed the airscrew a bit to the point where on tickover the flame altered from blue to yellow and left it like that. All good now.

[Rex]

I stopped Color Tuning any bike years ago, but especially now with E5/10 fuel.
Even years back using them on simple old cars like Morris Minors achieving the supposed optimum colour didn't always equate with the best performance.

[MathiasGFP]

What jets did you end up using? I have the same carb for my bike, and is right now fitted with a 200 main and 106 pilot jet, but was not running perfectly...

[chaterlea25]

Hi All,.
ye are mistaking the needle jet with the pilot
106 is the needle jet
Depending on the age of the concentric the pilot is either a pressed in bush placed opposite the pilot adjusting screw or a screw in jet in the same place. Very old and 2 stroke concentrics have a screw in pilot at the bottom of the main body.The pilot adjustment is the horizontal screw.
Needle jets wear out in not too many miles and if rich running cannot be easily corrected  needle and jet should be replaced

John