What a Difference a Notch Makes

Was having issues with a weak pressure pulse out the left side exhaust. Right side giving nice pop pop pops at idle, while left was more weazy and feeble. No amount of fiddling the idle air or throttle stop seemed to cure it. During a good run at highway speeds, noticed bike had slight power dips while cruising but went good at throttle up events. Plugs both looked on weak side, with light grey one right and much lighter/white on left side.
Decided was time to have another carb pilot clear out session, but while at it thought to try raising needles from middle to lowest clip notch, thus enriching the mixture.
Well, happy to report it feels like a new bike. Both sides much more equal at idle and just off idle for pressure pulses and sound. No more power dips while cruising along highway. Butt dyno says noticeable more pep when givin'er the beans. Sounds marvelous at blipping the noisey grip.
Just finished a longish highway run and waiting for cool down to check plug look.

This is with new amal premiers and after first over bore. Maybe stock setup guidance was too weak for the overbore?

Tornado said:

...but while at it thought to try dropping needles from middle to lowest clip notch, thus enriching the mixture.

Click to expand...

Raised the needles?

Lowering the needles weakens the mixture.

L.A.B. said:

Raised the needles?

Lowering the needles weakens the mixture.

Click to expand...

Thx, fixed in original post to read raising needles.

Yes always pay to have a play with needle setting I be doing the same soon just been playing with my old Amals they been in storage for over 9 years as I went down the PWK carbs from Jim set up for my Norton the bike ran great with them but always had problems with the right carb float sticking no matter how many times I did the little fixes to it and advice from Jim, didn't do it all the time but it got to the point I had enough, my old Amal's are still good as they replaced the original Amal way back in the 80s the slides are still good, pulled them down and gave them a good soaking for a few days, the Norton fired up first kick but the right pipe was running colder than the left then started to run on one cylinder till it conked out, so another pull down to find the pilot jet fully blocked had to do wire poke after another day of soaking in vinegar when blowing out with compress air I had my finger over the pilot hole and the blockage shot out and stung my finger, so all clear now, just got to fire it up now.
I fine with modern fuels the needle seem to work better on the lowest notch, middle setting seems to be a little lean but every bike is different so always good to have a play with the needle position to work out what is best for your bike and going by plug colour these days with modern fuels is not the same when we had lead in our fuel.

Ashley

Ok just checked plugs, both looking same, medium grey appearance, no more white and not sooty.

Yes my Mk3 with plastic airbox peashooters and headers with balance pipe run with the needle on the lowest clip, I have done a number of plug chops and plugs are a good colour.

lowest clip , or slot ON THE needle means the needle will sit higher, as he originally said.

On a bike with a fifty year history, using modern fuel, “stock setup guidance” can only be guidance to a starting point.

You have to tune your bike.

Tornado said:

Was having issues with a weak pressure pulse out the left side exhaust. Right side giving nice pop pop pops at idle, while left was more weazy and feeble. No amount of fiddling the idle air or throttle stop seemed to cure it. During a good run at highway speeds, noticed bike had slight power dips while cruising but went good at throttle up events. Plugs both looked on weak side, with light grey one right and much lighter/white on left side.
Decided was time to have another carb pilot clear out session, but while at it thought to try raising needles from middle to lowest clip notch, thus enriching the mixture.
Well, happy to report it feels like a new bike. Both sides much more equal at idle and just off idle for pressure pulses and sound. No more power dips while cruising along highway. Butt dyno says noticeable more pep when givin'er the beans. Sounds marvelous at blipping the noisey grip.
Just finished a longish highway run and waiting for cool down to check plug look.

This is with new amal premiers and after first over bore. Maybe stock setup guidance was too weak for the overbore?

Click to expand...

A detail which would be obvious to others but wasn't to me is when after inserting the slides following a needle height adjustment, the 2 screw holes in the cap should be in the correct alignment orientation without having to twist the cap to get the screws in. The spring can put a bias twist in the slide which will cause problems. The concentric could become eccentric.

BERT said:

A detail which would be obvious to others but wasn't to me is when after inserting the slides following a needle height adjustment, the 2 screw holes in the cap should be in alignment without having to twist the cap to get the screws in. The spring can put a bias twist in the slide which will cause problems. The concentric could become eccentric.

Click to expand...

I can see what you mean. I use the "corkscrew" method to wind the spring around the cable when installing or removing. So much easier than trying to hold it compressed while fiddling the needle in or out or r&r'ing the cable.