Question reagarding Spark Plug color.

i just removed my new Spark plugs after riding for about 200 miles.

it looks like the left one is ok, while the one on the right seems pretty dark. any suggestions from what settings i should change ?

thanks






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marc said:

i just removed my new Spark plugs after riding for about 200 miles.
it looks like the left one is ok, while the one on the right seems pretty dark. ]

Click to expand...

I would swap the plugs over and see if the condition moves with the plug. That will indicate if the plug is faulty. What igniton system are you running ?.

Its either rich or a missfire (weak spark ?) on the sooty plug.

i was running a Boyer Ignition with the old dual coil, that the previous owner put in. dual new premium Amals. today i just installed the CNW high output single coil upgrade.
with the old dual coil i was noticing some misfires after standing at a red traffic light.

i dont think the Spark plug is faulty, because the old ones looked just like that. I have a Trispark ignition on order.

marc said:

i was running a Boyer Ignition with the old dual coil, that the previous owner put in. dual new premium Amals. today i just installed the CNW high output single coil upgrade.
I have a Trispark ignition on order.

Click to expand...

I would check the float level on the rich plug side and the slide needle is in the correct position. Owners have reported float levels set incorrectly on new carbs.

I assume the 200 mls are on the old coils ?. New leads and plug caps ?

Trispark is a good system that will make the bike run and idle better.

With unleaded fuel the spark plug insulator should be white. Any darkening is caused by soot from incomplete combustion. Incomplete combustion can be caused by a number of things.

First I would confirm the health of the motor with a leakdown or compression test. Check the valve lift to make sure you haven't got a "flat" cam.

Then check the ignition system. Swapping parts from side to side will often help find the problem. It sounds like you have likely eliminated problems here.

Then to the most likely cause. One carb is either way too rich or way too lean or maybe the slides are way out of synch. Check the float level, and slide cutaway and make sure the needle jet holders are not loose. Blow out the passages with compressed air. See that the slides open the same amount. Make sure the bowls are not warped. A warped bowl from overtightening will not seal around the idle passage and cause problems. Sometimes rough edges or flashing on the plastic floats will cause the float to hang up on the needle jet holder and cause flooding. A small fine tooth file used to round the corners on the floats sometimes works wonders. Usually new carbs will need to have the inlet seat position adjusted to get the float level right. Jim

That plug is so intensely sooty-rich I would think the needle clip has popped out or the needle itself hung up . Or even bent from hasty assembly.

NGK plugs are usually good.
The Amal Premiers should have the Stay-up float that makes it easy to adjust float height. The white nylon floats are not very good; they usually need some trimming as above and they are too flexible. I vote for rich running right carb, either float level or idle mixture (the cheapest and easiest to adjust, too).

If the ignition system is good and timed correctly, and the carburation correct, the should be 2mm wide black band on the porcelain insulator right down inside the plug where it meets the metal. That sooty spark plug looks as though you might have a very slight degree of richness in one carburettor. Have you noticed petrol running from the carb overflow on that side ? (check the float needle and seat, and immerse the float in hot water to see if it is leaking.)

thanks for all the tips, i think i want to start by adjusting the right carb a bit leaner and see if the color changes.

how much should i change the Air Adjusting Screw, maybe half a turn in ?

Unlike other carbs, on an Amal the mixture screw controls air flow not fuel flow. Turning in richens the mixture, out leans it. Try quarter turns. As rich as that plug is I would be looking for other problems first, such as needle clip come loose or choke slide not lifting. Is this a problem that has just suddenly developed, ie they were both clean before?

Air screw only affects idle and that soot is not caused by idling, I hope. I would be looking at the float bowls and the fuel height in them. Air screw is adjusted for best or slightly rich idling.

Adjusting the air screw is not going to make much difference here. Once had this problem until noticed the one float itself was half full of gasoline ! Gasoline (modern ethanol even worse) being a powerfull disolver must have eaten an entry point at a thin spot. Ordered in ethanol resistant type stay ups new. Yes to checking jets have not come loose/unscrewed on that carb. Viton tipped foat needle seats better than original plastic type.

Just realized you have new premiers. If you had misfires from coil before changing coil then check all electrical connectors from pick up plate to sparkplug. A weak battery ?

What kind of riding have you done in those 200 miles?
Riding in town and relatively low speeds (up to 50 mph) I probably spend a lot of time between idle and 1/8 throttle, where idle mixture (air screw) has a relatively big effect. The idle system still feeds the carb throughout the throttle (it doesn't shut off or anything). Short trips also means frequent starts with more time with choke/enrincher on and less time fully warmed up. Slide cutaway has more of its effect off idle to about 1/4 throttle; however, this is more expensive to change. Then the needle/needle jet takes over more (costs nothing to raise or lower by moving the clip) in low to mid range. Main jet affects WOT but has some effect throughout the entire throttle range. There is a lot of overlap in the Amal circuits; more than the Amal tuning guides suggest. Just my experience/opinion.
Such a big difference between left and right plugs suggests right carb/valve adjustment, etc. rather than ignition.

Naw , doesn't matter how you drive for 200 . Pull the sick plug side and put in a new plug then tape the HT lead to the head body resting on it with the electrode exposed for your viewing of sparkages. In low light conditions start up the bike on one (the healthy cylinder) and look down to view the firing. Firing a strong white - blue spark regularly ? Then it's not electrical but carb nonsense.

Let us know what you come up with when you are done trouble shooting.

I would expect the bike to be very sluggish, if it was that rich on one side. Surely you must be able to see black smoke from the exhaust on that side when you rev the bike? If it is running on both cylinders , the ignition system is probably OK. I believe you've probably got something under the float needle tip, or a sinking float. I don't think you would have the idle or low end settings so wrong, that you would get that effect on the plug.

i am going to try to fix it tomorrow.

the bike is running quite decent, i think the right side is a little more smokey.

excuse my lack of knowledge, but what would be the proper procedure to adjust the carb more leaner ?

change the jets.

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

Check that the, slide, jets and needle position are the same in both carbs, and if they are not - set the one on the side with the sooty plug to be the same as the other. I will guarantee you have not got that problem. More likely to be flooding due to crap under the float needle, or a sinking float. Even if the idle/low range circuit is set dramatically wrong, to get a plug looking like that is unusual. If you've got flexible mounts, it is possible that one carb is hitting something while bouncing around causing the float needle to be jolted off its seat.