2003 KX125 Blowing up

marcusgunby · Mar 24, 2003

Yep its on order £20 -:(

steve125 · Mar 24, 2003

Besides making more power and having a better throttle response. This plug failure is just one of many more reasons to run race gas in race bikes!!

bclapham · Mar 24, 2003

whoooooaaaahhhhh. Is this time for another biatch fight girls?:) If handbags at twenty paces wasnt enough, maybe you two can have a tickling constest!;)

just to put things into perspective steve, it probably costs the same to put a gallon of gas into a car in the UK as it costs you to put a gallon of C12 into your bike, so we can only imagine hw much a can of 110 octane would be in the UK if one could actually find some. (and that was before the current jihad price hike).

although i am a stong perponent (is that a word) now of race gas, its hard to understand why this particular bike has this funky issue, any ideas steve, is it just something simple like cylinder temps?

steve125 · Mar 24, 2003

Bruce i'm so glad you find Marcus and I so entertaining! But be sure that when we fight that you can be there too! As we'll need a lady in a G string :scream:  to hold up the sign to let everyone know just what round it is! :laugh:

Team Green has always recomended race fuel in the kx's as they seem to run a fairly high compression stock. The ign. curve probably has a bit too much advance also. I don't feel it's an overheating issue at all. It has to be tough for Kawasaki to step up too the plate and spec an engine for power and have some people want it to run fast and trouble free on pump fuel.

Rich Rohrich · Mar 24, 2003

Marcus - Do you by chance still have a plug that was run in this motor before it failed?

Going back and looking at the picture, that piston sure looks like it has evidence of detonation on the exhaust side of the crown. Detonation could certainly break off the ground strap.

bclapham · Mar 24, 2003

steve and marcus remind me of these two

bclapham · Mar 24, 2003

back on topic, i wonder if a safety margin for this engine is just running two, or a thicker head gasket?

steve125 · Mar 24, 2003

Bruce if the kx had a head gasket that may work! :silly: But when you stack head gaskets, you also widen the squish clearance way out of spec. It's real important that the proper squish angle and clearance is maintained. So it's best just to increase the volume of the chamber bowl on a lathe.

bigred455 · Mar 24, 2003

Are the 03 kx 125's running the EIX series plug like the 250's.If that did cause the problem run the evx like last year.

dave186 · Mar 24, 2003

didnt NGK discontinue the EVX series and replace it with the EIX? I know i was having trouble finding an EVX for my KX.

marcusgunby · Mar 25, 2003

Rich its hard to see from this photo-im sending the full size one to you on e mail.I dont have the plug as i got angry and chucked it.However i did look at the electrode and didnt see any pits of aluminium from the piston crown.No hot spot on the piston underside-see pic

marcusgunby · Mar 25, 2003

heres the pic

marcusgunby · Mar 25, 2003

heres a pic of the spark plug

marcusgunby · Mar 25, 2003

I got another plug of the same type and broke the ground strap off by bending it back and forth-it has the same look to the part thats left on the suspect plug(broke just after the weld)

marcusgunby · Mar 25, 2003

Sorry rich i re read your post-the plug from before was the std one when i ran it in and it was jetted very rich-since then i have made a good few alterations.

I did notice a strange noise half a lap before it stopped, i changed down into 1st on a 2nd gear corner and it made a noise like piston slap-i was on a trailing throttle at the time.

 

those marks on the exhuast side are all damage from the ground strap being crushed by the piston.On undamaged parts i can see no sign of detonation.I took the head off the week before and it had 4 tiny pin holes from detonation and i lowered compression slightly to combat it.

DEANSFASTWAY · Mar 25, 2003

Theres some new plugs out now called VEX plugs meant for turbo'd tuner cars were trying them out in the micros now and on the MX bikes . They are like three side electrodes with like nor protrusion or nothing to break off . Maybe Ill let you know how they work out . NGK has alot of different plugs with different types of electrodes . Do you think on the KX its a matter of plugs breaking first or the motor parts breaking and hitting the plugs . Sort of like what came first the chicken or the egg? EH?

holeshot · Mar 25, 2003

Marcus:

Was the ring completely intact when you pulled it apart?

marcusgunby · Mar 25, 2003

The ring was totally untouched-nothing had hit the plug-i even found the ground strap bits in the exhaust so there wasnt any detonation problems IMO.If it was detonation the strap would have been erroded away.It had no cylinder damage at all so its just a case of the plug strap breaking.All i can say is check and recheck your plug.I got a friend to remove his head on his 03KX and he had no detonation so i think that one can be laid to rest.

steve125 · Mar 25, 2003

We will never really know why some KX's are breaking the ground strap off the plug. Is it just a coincidence? Maybe but probably not. Is the head stay putting too much pressure on the cylinder head and not alowing enough flex and could this stress the plug enough? It's a thought, but you would think it would blow the head O ring inner or outer first. IMO the shock wave from detonation is the most likely cause here. As in a jet ski engine i've seen it's effects in a way I would have never thought possible. To be able to loosen spark plugs that were repeatedly re- tightened in just a matter of minutes. That's how powerful the shock wave can be and at one time I had the plugs so tight I thought I was going to strip the threads out of the head. They continued to loosen until a ground strap broke off and ruined the cylinder. I never did change the type or brand of plugs i was using. I just took the right steps to stop the detonation and the problem never returned.

Rich Rohrich · Mar 25, 2003

Originally posted by marcusgunby
If it was detonation the strap would have been erroded away.

Not necessarily.

DEANSFASTWAY · Mar 25, 2003

I meant ZEX plugs. Everytime I see ring lands broken off or alot of times blown head gaskets the piston top has that funny black color and more prevalent around the outer edges. Did you guys ever try backing off the timing a bit on these and maybe it would yield more mid or top if its struggling and growling and banging away . Do they ever burn through the center of the piston? Ive got a quite a few fellows that I help out here with no problems so far.(NJ )Just wondering?

marcusgunby · Mar 26, 2003

 :whiner:

bclapham · Mar 26, 2003

OK, i see we have two theories

1. detonation is occuring at the plug, the strap gets hot and falls off.

2. we have some wierd wacko harmonic humm that causes the strap to fall off.

if 1 is the case, then why arnt we seeing detonation elsewhere in the engine, ie. on the head and on the piston? is it just the head specs that are causing the heat to be transferred only to the plug? The problem has occured with lots of different riders accross the world, i am sure all of these bikes are ridden differently, diff oil, fuel, diff jetting etc. etc. are we totally sure detonation is the issue. Surely, an experienced guy like marcus would be able to tell if it was detonating, since it seems like he has taken every other bike he has had to this point and back, probably using the same fuel and oil without this happening.

so lets assume that 2 is the case, how can we prevent this harmonic hum? provided that we are not relying on the head stays to act as a heat sink for the head, I am thinking that you could run some of those rubber backed washers on each side of the head stays. i know it would be messy, but what about coating the head stay bolts with a good lather of silicone bath sealer to maybe cut some buzz out there, just like some people do with handlebars?

Rich Rohrich · Mar 26, 2003

Marcus - I looked at the pics you sent me, and now that I can see the detail I understand why you believe the ground strap did all the damage. from the looks of it I'd agree.

Are you seeing any indications of detonation on the plug, like little specs of carbon? How far back on the ground strap does the timing "burn" extend?

Bruce's thoughts on isolating some of the vibration seem well worth looking into.

bclapham · Mar 26, 2003

hey rich, i tried to pm you again but your box was full, seems i got a bit over zealous/excited about trying to figure what cylinder to buy, but i managed to get through to eric again and he has all the bases covered for me!:)

ps. back on topic, can we assume (sorry thats the second assumption i have made today)!;) that since the head stays are aluminium, that they arent relied upon to take any heat away from the head?

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