Hi all, I own a 110ccm Honda Scooter, 4 stroke, carburetor and CDI for ignition, over the time I owned the bike, I had to replace the spark plug 3 times because they failed.
I have 40 years of 4 and 2 stroke experience but this I can not understand, is it possible that there is something wrong with the ignition coil?
I am living in a place where nobody has the equipment to check anything, the plugs fail in about 2-3 months and have no signs of damage.
Thanks
What do mean by “failed” and “no damage”? What color is the electrode ceramic on the failed plugs?
How did it fail? What was the failure mode?
When they don’t work anymore, the plugs are wet and black, they fail mainly in the way that I have a hard time starting the bike and it will not drive nicely anymore, like cutting out and after two or three days they are death.
sounds like they’re being fouled. Spark plugs usually don’t up and fail. especially with such a short lifespan. most of the spark plug “failures” I’ve seen are on old plugs where the electrodes have eroded to the point the spark can no longer reliably jump the gap. if they’re wet and black and not reliable within 2-3 months, it sounds like you could be running too rich, burning oil, or the ignition system is conking out and you’re experiencing a lot of misfires.
which would be where? Is it possible this place still has leaded gas available?
This. Have you tried cleaning these plugs and reinstalling them to see if they work again when cleaned? If so, then the plugs aren’t failing, they’re just dirty - and they’re getting dirty because something’s wrong with the rest of the engine.
Are you having to add a lot of oil on a regular basis? Got bluish smoke coming from the exhaust? If so, your piston rings and/or cylinder bore may be damaged. If you’re lucky, this can be fixed by re-honing the bore and replacing the piston rings (possibly also the piston). Another possible cause is a leaking intake valve stem seal. Oil can be drawn past this seal at idle, when you have high manifold vacuum; then you tend to get a puff of bluish exhaust smoke only when you accelerate away from stops (as the accumulated oil gets drawn into the cylinder, and not so much when cruising. You don’t usually get a lot of oil in there if that’s the problem; if you’ve got an oil consumption issue, it’s almost certainly the bore/rings/piston.
Has fuel economy gone to hell? If so, then something’s wrong with your carburetor. Maybe the choke is staying on too long? This should only be needed during cold starts; if you’re leaving it on while cruising (or if it’s sticking on even though you’re flipping the choke lever off), then it’s dumping too much fuel into the engine, and the excess is burning incompletely and wetting/fouling the plug. If it’s not the choke, then there’s something else wrong with the carb, and you’ll want to take the scoot to a small-engine service shop.
The plug is getting fouled, and is a symptom of the problem, not the cause of it. If it’s oily, you have a mechanical problem as described above. If it smells of gasoline when wet either the spark isn’t hot enough to burn the gas properly or there’s too much fuel going to the cylinders. The most likely causes for the former possibility are a weak ignition coil or faulty plug wire; for the latter it’s a faulty carburetor.
IF it’s fuel fouled:
One quick check of the plug wire is to spray some water mist on it while the engine is running. If it misfires or dies replace the wire. A basic test of the coil is done by seeing how far the spark jumps from (a wire connected to) its secondary terminal to a ground point while cranking (make sure the wire doesn’t short to ground along the way). There should be a strong crackling spark of ¼-½" (google on this to get detailed instruction and more info).
If you’re as sure as you can be that the problem is not in the ignition system, repair or replace the carburetor.
You didn’t specify whether your spark plugs are in the correct heat range for your machine and the type of driving you do. Have you confirmed that you do, indeed, have the correct plugs? They can be the same size and shape, but their heat range can be different.
And stay away from Champion plugs! In my experience, they foul far faster than any other brand. Don’t know why. Doesn’t make any sense. Get yourself a nice NGK in the proper heat range.
because they don’t.
Not to offend anybody but I wrote “40 years of experience”, what do you believe why I came to the all-knowing Dope Board, because despite of all the work I did on all my bikes I am not getting this.
The bike is 10 years old and has only 6000km on it, it was owned by an American that did some funny mods to the bike but I did not see anything changed in the ignition setup, in the beginning I believed that it must be the carburetor because spark plugs fail rarely on 4 strokes.
Thanks
I am on a small island in the Philippines for the one that needs to know…
Have you tried cleaning these plugs and reinstalling them to see if they work again when cleaned?
It has to be getting too much gas or oil leaking into the combustion chamber somehow. By “funny mods” I wonder if the PO opened up some carb jets to “make more power”? :rolleyes: Does it have good compression? You haven’t replied about the nature of the black on the plugs - fluffy black carbon from a rich mixture can short out a plug - try opening the gap. Oil fouling looks dirty and greasy…
There are lots of Honda Elite 110 parts on Ebay. It appears that the scooter uses a carb (also on Ebay) but also a full fledged engine control system so you may be screwed. I agree with cleaning the plug, open the gap, and trying again. The coil looks to be a dedicated Honda part but if there are only 2 wires in, ground, and plug wire you *-could- *jury-rig an automotive type coil for an improved spark (or at least from a known good coil). Don’t know if that would affect the CDI.
You have 40 years of 4 and 2 stroke experience and you dont know how to diagnose and determine the cause of fouled plugs?? 
Completely disagree with randomly “opening” the plug gap. At the most set it at the loose side of its normal gap.
Also, opening up the jetting to make more power could be the problem if the previous owner went way, way over board. Doubt an engine this size has screw-in jets.
As far as cleaning and regapping the plug, that’s a bad idea. A small piece of steel is VERY likely to fall into the sticky carbon around the insulator and later vibrate its way into the combustion chamber working its way between the cylinder wall and ring. Scrape, scrape. Plugs are too cheap to chance this.
Also best to check for proper heat range for plug as mentioned above. Is the plug wire solidly attached to the plug brass connector? A shot of WD-40 will make it easier to connect and disconnect in the future.
After 50 years of riding bikes, diagnosing this from a distance does seem to point to mechanical problem. You can pour more money into fixing it than it’s likely worth (hate to have to say that), or replace the plug and sell it and buy something a little newer. Next bike, remember to ask to look at the plug before you pull the trigger on it. Bring a plug wrench, both sizes, in case they say they don’t have one.
Phu Cat
Could this be fouling due to damaged piston rings allowing oil to mix with the gas?
I have a substantially older Honda 110 trail bike and have had problems with the plug wire simply wiggling off. This gives a somewhat similar set of symptoms to a bad plug: the bike won’t start, there’s spark at the wire, pull the plug out and it’s wet. The first time it did it I figured, aha, bad plug and replaced it and it ran great for another couple months. Then it did it again and I said “heywaitaminute” and put the old plug back in and lo and behold it fired right up.
Just wiggling the wire doesn’t seem to fix it-- I had to actually pull it off and put it back on. I figure there’s probably something internally wrong near the 90 degree bend in the boot or something. Annoyingly on that particular bike you can’t just replace the plug wire without the coil, so I’ve just been kind of living with it and popping the wire off and on and using some electric grease. I imagine if I used it for regular transportation I’d drop the $10 to fix it.
Thanks again, I will try to be more specific, the plugs are not fouled up with oil they are black because of the bad combustion when the engine runs cutting out and they are wet because they don’t fire anymore. I had the plug resting against the engine and had it turning over with the starter (by the way this is a Honda XRM that is only sold here as much as I know. Honda XRM - Wikipedia), the other plugs, not the last one, did produce a spark sometimes after cleaning, the last one is totally death. Somebody mentioned the coil, I was wondering what fault could damage the plugs but have no clue, and I bought the plugs at different places because we know that the Philippines is the dumping ground for factory defect/reject, I will buy a new one today and hope for the best…
Huh. Only in the Philippines. Neat little bike! An “underbone” ??
Does a brand new plug produce a strong looking spark? Try it before installing it in the engine this time. A new plug may have some sharp edges that will initiate the spark with a weak ignition and may require more voltage as they get burned off. But in my experience, almost any plug can be made to spark and run to some degree.
The problem has to be fuel mixture, oil leak, coil, plug wire, or plug connector. There’s just nothing to fail inside the plug.
As one can see and as I experience myself in the past, spark plugs do fail but rarely.