Idle Problems

Hi Gents,
Having a lot of trouble with the idle on P11. So far this is the work i have done. New valves and seats cut, set valve clearances at 6 and 8 thou, carbs are 930, re-sleeved slides, main jet is 310 but have ordered 250,106 jets, needle position middle, float heights checked, timing is 28 and 29 at full advance, choke slides up, all carb faces have been checked for leaks, changed plugs and checked plug gaps, coils are 12v and both 4.3 ohms resistance.
It will run on either cylinder by itself with a very even idle but as soon as i adjust the idle to bring the other carb up it turns to poo. Anyone got an suggestions.
Cheers

Many idle problems are sometimes caused by worn or sticking auto advance units. Electronic ignitions such as Tri Spark, Pazon & Boyer solves this issue. Good luck.

I believe you meant to say your current main jet is "210", not 310. From my experience, the factory reccomended specs work. From your discription, it sounds like something isn't right... My top suggestions are:

check for an air leak on the intake manifold- spray around the outside of the manifolds with carb cleaner to see if it effects the running bike. If it stumbles when you spray it, air leak!

Buy one of those "Pin vise sets" which has numerous micro-sized drill bits that can be chucked in a pencil-like stylus and use the proper sized bit to unclog the idle jets of each carb. There are also tiny ports in the amal bodies behind and in the inner body area that must not be clogged.

Check that the needle clip has not come undone on one of your carb bodies. You may be able to see the inner carb bodies go up and down by eye, but I usually use a finger inside the carb to feel for the movement of each carb needle as I lift the slides. This makes sure the needleclip is on the needle. The needle clip could also be dislodged from it's seat and caught in the spring making it feel like it's seated properly.

As Jerry said, points... really, in this day and age? Keep them in a bag on your shelf so the original parts are always available for your bike's collectability sake, but I would swap them for a boyer and single lower resistance coil. I think the last time I touched any ignition parts was 2 years ago when I was sorting out my main jet size and playing with timing advance. Before that it was only to change from my original boyer, to the micro digital box. They usually work perfectly or not at all, so they are easy to trouble shoot.

Add some extra grounds to your engine. Sometimes a poor ground on the engine causes a weak spark. On a commando's isolastic mounting a poor ground is even more probable to cause a weak spark, but good grounds are important for a good spark.

A bad component- A very long time ago I had a bad spark plug that tortured the life out of me. I think it had a cracked insulator up inside the electrode, so It sparked at the tip when I spring clamped it in place ON the head of the bike, but when I threaded it into the cylinder, it misfired intermittently. I pulled my hair out on this for days on end. A friend who was going out to town said, "let me get you new plugs, what are those?" I told him that "I tested the plugs and they are good!" He got me plugs anyway, which I put in the bike just to appease him, and the bike started and stayed running on the second kick... That's how I learned about intermittently bad plugs, so change yours....

Connie73 said:

Hi Gents,
Having a lot of trouble with the idle on P11. So far this is the work i have done. New valves and seats cut, set valve clearances at 6 and 8 thou, carbs are 930, re-sleeved slides, main jet is 310 but have ordered 250,106 jets, needle position middle, float heights checked, timing is 28 and 29 at full advance, choke slides up, all carb faces have been checked for leaks, changed plugs and checked plug gaps, coils are 12v and both 4.3 ohms resistance.
It will run on either cylinder by itself with a very even idle but as soon as i adjust the idle to bring the other carb up it turns to poo. Anyone got an suggestions.
Cheers

Click to expand...

have you blown out the whole of the pilot system in each carb prior to fitment?

It currently has 310 main jets but i have ordered 250, i have had the bike running and checked for air leaks already, i have changed plugs with ones from a running bike, all jet passages have been prodded, cleaned and blown through. Think i might pull the carbs from another bike to rule out the carb area. The AAU is where i think i will go next along with checking the grounding.

Il check back and let you all know after another week.
Thanks all for your replies

1 duff suppressor cap that will not fire on tickover, I’ve had one on mine so don’t ask me how I know

Hi.
If you have the stock 930/7 and 930/8 Amal you must fit the external n. 25 pilot.
Without external pilot you cannot have any idle.
In any case the stock setting is 250/25/107, cut 3 slider.
Piero

pierodn said:

Hi.
If you have the stock 930/7 and 930/8 Amal you must fit the external n. 25 pilot.
Without external pilot you cannot have any idle.
In any case the stock setting is 250/25/107, cut 3 slider.
Piero

Click to expand...

+1 I haven't fired mine up yet but that's the same numbers that Piero quoted. You will find it also in Roy Bacon Norton Twin Restoration (Needle position is not listed so start with clip on middle position). Amal site gives the same data, again no needle position listed.
http://amalcarb.co.uk/carbspec/carburettor/spares/id/5464/
I would also play with a .106 needle jet to suit today's gasoline mixtures (Maybe???), but use the base numbers above.
Cheers,
Thomas

SAGA OVER.
After pulling what hair i have left out. I eventually found that even though i had bought new plugs, one failed when installed into the head. The plug fired when against the head checking for spark but must have been a different case when trying to ignite the mixture under compression. Currently after buying new plugs and after a half hour run yesterday the plugs are black on the outside and the porcelin is white to tan. Yay. I have ordered 250 mains although it runs fine on the 310. Its also, running 25 pilot, 106 needle, 3 cutaway, top notch on the needle. 95 octane fuel.
Just needs a new inner primary now as the PO had put spacers anywhere he wanted and pulled the case at the rear towards the centre causing a crack at the front.
So, thank you all for your support.
Much Appreciated
Ross