Misfire LH cylinder

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Where is your ims on the suspect carb/cylinder? If you're moving down to #30 pilots then you've probably been winding the ims out to the point it's ineffective. Turn it out to 1 1/2 turns and tune from there. I suspect you are out more than 2 or 2 1/2 turns indicating need for a leaner pilot which you have on the way w/ the norton specific needles. I'd wait for the new parts, install the needles first and go from there.

The jrc engineering guys are super! Some of their distributors are not
 
Me again.

How did you determine that it was your left cylinder?

I got some thoughts either way you answer this.

RS
 
If not go looking for the bit you threw away in the bushes
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and

What Must Always be Kept In Mind is Anything Can Cause Anything in a Commando
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What I gather from this is the difference between a living, breathing machine that you have to coax and cajole and sometimes sensibly persuade into doing the thing it was built to do versus a modular collection of transducers that only fail when their digital brain has a short-circuit. While the former doesn't give you any joy (as has been said), it does give a host of analog information that may take a bit of searching, testing, and not just a little skill to interpret. The latter is only a matter of connecting a diagnostic tool to a certain port and there you are, answer is forthcoming 101011101001010101101. Whatever.

By the way, I don't have a clue what's wrong with your bike :)
 
JimC said:
Brit Iron Motto is if if runs like fueling, makes noises like fueling, then think electrics.
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95% of carburetion/fuel problems are electrical.
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Is the reverse true? Are 95% of all electrical probs fuel-related? If so, it's time to consider poor fuel delivery, Although you would logically believe fuel delivery would be less of an issue at idle than higher-rpm running. But not if an idle circuit is partially clogged. The problem would go away as soon as the motor came off the pilots and onto the needle jets.
 
RoadScholar said:
Me again.

How did you determine that it was your left cylinder?

I got some thoughts either way you answer this.

RS
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Simply feeling the exhaust pulses. I'm out more than 2 turns so am awaiting the smaller pilots and norton needles.
 
1. You can Not set pilot-idle air screw to 1.5 and expect to be able to tune around that. What determines the pilot turns is the float level and crud in pilot jet.
1a. Yes too small a jet and/or too big a slide cut out would require more screw turn out to get some idle ability.

2. Yes electrical symptoms like stuttering then fine idle or throttle response can be a mixture supply problem not electrical. I've had balance tube to lost carb bolt make me waste time on electrics till wires lead me straight to carb problem.

3. worser senario was just testified to, sticking valve guide.

Welcome to obsolete Commando manhood will power and intelligence testing er a, strengthening hobby.
 
arcadian,

For what its worth, I went nuts a while back sorting a misfire at idle. Engine was lumpy at idle, no amount of carb fettling would fix. I never suspected ignition, cause I expected that to show at at normal rpm more. Eventually I got me a leakdown tester, and guess what after buggering around for weeks and even replacing the Amal bodies I had a leaky exhaust valve. With the LD tester on and about 50psi I stuck my palm over the end of the peashooter and after leaving it there for a moment and then removing I could hear and fell a whooomp of air. So now that you are at this stage if you can get a LD tester, I would add it to the tool kit. Really useful gadget.

foot note.

A couple of years on to present time, experienced similar crappy idle, took me a week or to think about doing another leak down. And another leaky exhaust valve, so that prompted me to tear her right down, this time a new set of PM black diamond valve, springs etc. And als doing the JS eng light pstons and doing first rebore.


anyway, a process of elimination, just folow the steps and don't get bogged down with only ingredient, from my experience I noticed the leaky valve shows up most markedly at idle speeds, than general running.

Cheers Richard
 
stockie1 said:
arcadian,

For what its worth, I went nuts a while back sorting a misfire at idle. Engine was lumpy at idle, no amount of carb fettling would fix. I never suspected ignition, cause I expected that to show at at normal rpm more. Eventually I got me a leakdown tester, and guess what after buggering around for weeks and even replacing the Amal bodies I had a leaky exhaust valve. With the LD tester on and about 50psi I stuck my palm over the end of the peashooter and after leaving it there for a moment and then removing I could hear and fell a whooomp of air. So now that you are at this stage if you can get a LD tester, I would add it to the tool kit. Really useful gadget.

foot note.

A couple of years on to present time, experienced similar crappy idle, took me a week or to think about doing another leak down. And another leaky exhaust valve, so that prompted me to tear her right down, this time a new set of PM black diamond valve, springs etc. And als doing the JS eng light pstons and doing first rebore.


anyway, a process of elimination, just folow the steps and don't get bogged down with only ingredient, from my experience I noticed the leaky valve shows up most markedly at idle speeds, than general running.

Cheers Richard
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This is what's been cited by others as well. My glass Dunstall tank was lined a second time after discovering a leak. I suspect some resin made it's way onto the valve stems. As noted, the problem only manifests at idle range, anything above she purrs like a kitten. This one little niggly fact is what's been pressing me to lean towards a fault other than the ignition system. Last night I swapped out the coil for a known working version, as well performed the boyer plate tests mentioned. Problem persists.

I'll save this for a winter project, and simply deal with the idle as a fact of life for now. When I get the head off over the winter, I think I'll reline the tank with the fresh jug of Caswell liner I got sitting on my bench.
 
ims?

I've worked out what it is but still no idea what IMS stands for, someone put me out of my misery please.
 
IMS?

Idle mixture screw? Otherwise known as a PAS, or a VCS.
 
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