Anyone had this happen to a sparkplug?

**Racey Rider** · 20th March 2005, 17:53

Spot the difference.

http://www.kiwibiker.co.nz/forums/at...achmentid=8512

While doing some more testing of my motor before the coming Winter series, things went wrong. Cutting out. running rough. What Now moments??

On pulling out the plug, I see it has broken off the insulator!
And where is the insulator?? Bouncing around on top of my piston!

After a bit more running, it seems to have been blowen out the exhaust now (I hope so anyway!).

Not Happy!

**Teflon** · 20th March 2005, 18:49

Yeah, this has happened to me with NGK EV's. No problm with the standard plugs.

**Motu** · 20th March 2005, 18:56

Detonation.

**Racey Rider** · 20th March 2005, 19:01

Detonation!
I have had a few problems with the rotor coming loose and stuffing up the timing lately.
Poor little motor

**Ixion** · 21st March 2005, 02:18

Originally Posted by Motu

Detonation.

Yep. Believe the man. Massive preignition. The ceramic can't handle the shock wave. Next step is usually a hole in the piston. Or a broken conrod.

I've had it, even had the ceramic core blow right of the metal body. Has you been trying to increase your compression ratio and gotten too greedy? That's what did it for me anyway.

**Jantar** · 21st March 2005, 08:13

I have had a similar experience with AC Delco plugs in two strokes back in the 70s. They would either lose the porcelain, or keep the porcelain and lose the electrode. Either way it was still a hole in the piston.

**F5 Dave** · 21st March 2005, 11:32

As stated probably not the plugs fault. NGK are great plugs but detonation will destroy pistons so a bit of ceramic insulation will get killed as well.

Detonation isn’t actually pre-ignition per say, pre ignition happens before Top dead centre Pre spark (hence the name). Detonation is the uncontrolled burning of the end gasses & is basically an explosion rather than a controlled burning of the gas which normally occurs.

Contrary to popular opinion the piston is not shoved down the bore by an explosion. The burning of gas raises the temperature & (Boyle’s law) hence the pressure, pushing the piston down increasing the volume, reducing the pressure etc. Yawn, sorry.

**Motu** · 21st March 2005, 12:16

I like to think of detonation as post ignition,as it always occours after the firing event,of course pre ignition happens before the firing event.A motor can live with a certain amount of preignition,but post ignition will almost always damage something,in the days of cast iron rings a top ring would sometimes be shattered.Those deposits on the earth electrode could possibly be piston material....oops...

**Racey Rider** · 21st March 2005, 13:27

Originally Posted by Motu

Those deposits on the earth electrode could possibly be piston material....oops...

I guess thats a bad thing ha!

Well it least I'm learning lots as I DIY on a cheap bike.
Motor is still running.
The next thing to learn will be, ' will this piston now make it through the first race day ' as I can't afford to change it before then.

**Ixion** · 21st March 2005, 13:55

Originally Posted by Motu

I like to think of detonation as post ignition,as it always occours after the firing event,

Um, yes. Post ignition . My bad. The mixture explodes like a bomb instead of burning with a nice tidy flame propogation.

Though you can get both at the same time - preignition that sets off detonation.

**Motu** · 21st March 2005, 14:39

Originally Posted by Ixion

.
Though you can get both at the same time - preignition that sets off detonation.

Yes - detonation is usualy caused by pressure from the flame front spontainiously igniting the remaining fuel,just like a diesel - pressure means heat.It's a hell of a lot more complicated than just saying pre ignition or detonation,you gotta find out what it is and what caused it.

**Racey Rider** · 3rd April 2005, 18:01

Well after a number of different problems lately with the KR150,
She (/He, Haven't yet decided) finally gave up today.

Have been trying to sort this motor for a while, seizing it a number of times, and always surprised that after a full throttle seizure, it started up again, given 30 seconds to cool down. Tough Motors these Kawasakis!

Pulled the plug after yesterdays lockup to find flakes of piston all over the electrode. That surprised me as I hadn't felt the detonation happening as I thought I had times before. Had switched to Pre mix 91 as I wasn't confident the oil injection was working 100%. A hard run up the road (after warm up), had it seizing. After this happens a few times you get really good at covering the clutch so it can be disengaged at the first sign of trouble.

So today the next trial was to use pre mix 96 to stop the detonation. But alas, Bike wouldn't start. I knew straight away what that meant.
No compression.
Half an hour later the barrel was off and revealing the damage.

http://www.kiwibiker.co.nz/forums/at...achmentid=9026
Rings wielded in on the exhaust side. Crater forming in the centre of piston. Lots of indentations on piston and head, - a mix of Detonation and spark plug electrode that had broken of previously.
But the worst problem, a couple of srcatches in the barrel.
Piston/rings can be replaced, and I have a spare head.
But I'll have to sand down the scratches in the barrel. Hopefully it will still be ok,, I only just got this replacement one!

Oh well,, Thats the joys of 'Learn as you Go"!

**Jamezo** · 3rd April 2005, 18:52

detonation problems? how about this?

http://www.nexusmagazine.com/articles/Firestorm.html

http://www.robertstanley.biz/firestorm.htm

it seemed a bit seedy when I was told about it, but now I think it's a real technology. could a mechanic or something tell me if that is what a normal spark plug looks like; being fired on the right in the demonstration animation in the second page of the second link?

**Zapf** · 3rd April 2005, 23:32

anyone tried these then?

http://www.eautoworks.com/productima...one_detail.jpg

had them in a corolla when I was heaps younger, and it felt that they do give better engine response / pull...