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Message started by Steve H on 10/12/14 at 08:50:03

Title: Question about spark plugs
Post by Steve H on 10/12/14 at 08:50:03

My son has a 110cc chinese dirt bike that is killing spark plugs. Over the last couple months it's killed 3. I just bought a new one last night for him.

When the plus dies, it is black. Usually by the time he tells me it won't start, he's kicked it so much it's flooded and the plug is wet. These plugs have no other signs of damage. The gap is right. No signs of overheating. No chips on the insulator. No matter how much you clean or anything, they never fire again.

It came with an A7T in it. I got a champion equivalent last night. We'll see how it holds up.

Does it sound like I should go to a hotter plug?
Any ideas suggestions?

Thanks
Steve

Title: Re: Question about spark plugs
Post by Kris01 on 10/12/14 at 10:04:43

Black plug = running rich

I think :-?

Title: Re: Question about spark plugs
Post by Serowbot on 10/12/14 at 10:52:55

2-stroke or 4-stroke?...

Title: Re: Question about spark plugs
Post by Dave on 10/12/14 at 17:12:12

If you have the plug the manufacturer specifies, and it is killing plugs and making them black....you either have an over rich fuel problem or an oil burning problem.

Sometimes you can change a heat range up or down to correct for riding style....a hotter plug if you are always at low rpms and a colder plug if you are always riding at high rpm....however it sounds like you have a problem that is not the fault of the plug.

Title: Re: Question about spark plugs
Post by stinger on 10/13/14 at 00:17:20

Maybe this will be of some help!

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Title: Re: Question about spark plugs
Post by old_rider on 10/13/14 at 18:06:27

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Title: Re: Question about spark plugs
Post by Serowbot on 10/13/14 at 18:12:32

That's Greek to me... :-?...

Title: Re: Question about spark plugs
Post by MMRanch on 10/13/14 at 22:00:41

So run some "SeaFoam" through the fuel system to clean the sticking Carb-float , its running rich = sticking float. ;)

I've got a China 4 wheeler with the 110 motor , we've put it through a lot in the last 11 years and it still keeps cranking up for more ! :P

I'm under the impression that the Iridium plugs need less voltage and are kinder to your electronics . :-?

good luck with it :)

Title: Re: Question about spark plugs
Post by Steve H on 10/14/14 at 04:07:59

Thanks for all the replies.

I just had the carb apart about a month ago. Everything seemed fine. Float works nice and smooth. There are no signs of any build-up. I will pull apart and check it to make sure. The carb on this bike has always been next to impossible to keep adjusted but the bike has never killed plugs until the last few months.

Nothing has changed with the condition of the bike that can be seen. Nothing added. Nothing removed. Using the same gas. Same riding area and style. Not burning oil. The level never changes and there are no oil leaks.

Thanks for the tip on the iridium plug. If I can find one, I'll give it a try. The bike has gone through 2 CDI boxes. At $6 each, it's not a big deal. I try to keep a spare around these days just in case.

Someone asked, it is 4 stroke. I just set valve clearances a couple months ago.

I have no clue what the manufacturer spec'd for a plug. No manual, no manufacturer name, no sticker on the bike, nothing. It's got the same type plug that was in it when I got it.

Title: Re: Question about spark plugs
Post by Dave on 10/14/14 at 04:28:50

The plug is flat black sooty....black - or black oily shiny....black?

Title: Re: Question about spark plugs
Post by Tocsik on 10/14/14 at 07:29:17

If you've replaced the CDI a couple times, maybe check (or replace) the coil, too.
Does it use a stator? Maybe it's putting out too much juice? The CDI and coil should take care of that, though.

Title: Re: Question about spark plugs
Post by gizzo on 10/14/14 at 14:01:12

While we're talking about plugs, can anyone explain exactly why spark plugs die? I don't mean fouled up dying, they can be cleaned and go again. But especially two strokes back in the day, used to go through plugs. They'd work then they'd stop working. why? There's no moving parts, the electrode never wore out, just the plug would not work. My car, too. Needs plugs changed every 20,000km to work at it's best. Other vehicles I've seen plugs go over 100,000km.

Title: Re: Question about spark plugs
Post by verslagen1 on 10/14/14 at 14:27:44

3F252123221C2D3E383E25282B294C0 wrote:

Ceramic is porous, carbon is conductive, cleaning only removes surface contamination. QED.

Title: Re: Question about spark plugs
Post by gizzo on 10/14/14 at 15:19:18

So you're saying the ceramic insulator becomes porous, absorbs carbon and becomes conductive, the spark takes the easy way through the insulator to the block instead of jumping the gap? And 2 stokes kill plugs soonest because they make more carbon? Sounds plausible, thanks. I wonder why spark plugs on stationery engines last so many decades. They're not famous for being oil tight or incredibly efficient. Maybe it's the sheer mass of ceramic in them resists absorbing carbon.

Title: Re: Question about spark plugs
Post by Steve H on 10/14/14 at 17:05:51

There's no oil on the plug. Usually by the time I get to it, he's kicked it enough to thoroughly flood it. So, it's soaked in gas. When it stopped the last time, I got to it before he flooded it. The plug was flat black. Not sooty, just black. No sign of oil. Gap was fine.

Tocsik, good idea about the coil too. I might just have to order one and give that a shot too. It does use a stator and is AC powered. I found a web site one time, forgotten now though, where they told the voltages you should be getting from the stator. It was perfectly in line with what they said.

I have checked the wiring from one end to the other. It is all great. No sharp bends, no scrapes. All wire runs conductive. No shorts to ground.
There's nothing to it really. One coil stator, ignition pickup, CDI, coil, kill switch. It can't get much simpler.

Title: Re: Question about spark plugs
Post by Dave on 10/14/14 at 17:36:46

Back in the day we also had lead in the fuel.....and that may have also contributed to the fouling.

I suggest you put in a good plug, and run it for a bit, and take it out while it is still running good and see what the plug looks like.

It could be that your electrical system is crappy, and the plug only reflects the fact that when the system is breaking down and not making spark, the cylinder is dumping a bunch of fuel on the plug when it doesn't fire. The plug may not be the cause.

Title: Re: Question about spark plugs
Post by Dane Allen on 10/14/14 at 17:49:52

Not to hijack a thread but I just passed 21,000 miles and am still on the original plug, does that mean my engine is running cleaner or is it a luck thing?

Title: Re: Question about spark plugs
Post by Kris01 on 10/14/14 at 18:07:44

A copper plug will last 30K or more. ;)

Title: Re: Question about spark plugs
Post by Steve H on 10/15/14 at 20:40:58

Update:

The plug was dead. It wouldn't fire on anything I connected it to. New plug wouldn't fire on the dirt bike but would on everything else.

Swapped out CDI. Started first easy kick.

I ordered a spare. Something like $5.49 with free shipping.

I saw a post on a site about chinese 4-wheelers where a guy that sold and serviced them said there is a 30 to 40 percent CDI failure rate within the first year. He generally had 10% failure straight out of the box.

Guess they are using lots of marginal components to make them cheaper.

Thanks for the help and ideas, everyone.

I do think I might order a coil too. If it kills it again, change them both at the same time.

Title: Re: Question about spark plugs
Post by Dave on 10/16/14 at 04:50:07

If the thing remains troublesome.....is the thing a close enough copy of the Honda engines that you could install the parts from a real Honda engine?

I just can't imagine that a $ 5.49 CDI is built very well.

Title: Re: Question about spark plugs
Post by Dane Allen on 10/16/14 at 15:27:16

546F6275646873756E666B74070 wrote:

Nothing Chinese is built very well >:(

Title: Re: Question about spark plugs
Post by Steve H on 10/16/14 at 15:49:04

It's a very close copy. But, you know. Half a mm here and there and things don't fit.

It started and ran about 3 minutes today then stopped. No spark. Not a bad plug. Plug is slightly sooty but the bike was choked for about half the time it ran. Changed the CDI for the new one in the box, still no spark. Checked outputs from the engine. They look good. Stator and pulser. checked continuity of other wires. Disconnected kill switch.

Everything fine. Looks like I'll be sourcing a coil tomorrow. That's the only thing I don't have a replacement for and I am sure one of my spare goldwing coils won't work on it. They are huge compared to the one it has.