calling all spark plug readers

cleareforlanding
Edited Date/Time 5/3/2015 8:18pm
Alright fellow vitards, not a good day at the races last night, lol. Holeshot and rode well in first moto of both my classes, but second moto lost a few rear spokes on the kx and had to jump on my rm as back up bike. Gate drops 2nd moto, hammer the throttle, halfway down start straight.....bwaahhh and silence. Motor has...had 7.7 hours on it, always ran 927 at a 32:1 w c12, oil changed every two rides w airfilter changed every ride. Pulled the plug at the track and this is what I have......what do you guys think I am going to find when I pull the jug??? Last two test I had fired it, seemed a bit sluggish and down on power, assumed it was jetting.








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ianhendry46
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ianhendry46 5/3/2015 9:00am
5/3/2015 9:00am
I'm not sure if it's just the picture, but the plug looks wet to me. Also it looks like she's running a bit on the lean side. What are the sizes on your pilot and main jet? Needle clip position?
Matt Fisher
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Matt Fisher 5/3/2015 10:42am
5/3/2015 10:42am
That's either silica (dirt) or bits of aluminum on the plug. Sad
Dirt would be from something like an air filter with a bad seal, torn intake boot, etc. Needs a top-end and usually a new crank too.
Aluminum is usually from detonation. Old gas (if your C12 was stored in a plastic container), air leak, lean jetting, etc. Normally needs a new top-end, but cranks are often okay.
cleareforlanding 5/3/2015 12:29pm
5/3/2015 12:29pm
Matt Fisher wrote:
That's either silica (dirt) or bits of aluminum on the plug. :( Dirt would be from something like an air filter with a bad seal, torn...
That's either silica (dirt) or bits of aluminum on the plug. Sad
Dirt would be from something like an air filter with a bad seal, torn intake boot, etc. Needs a top-end and usually a new crank too.
Aluminum is usually from detonation. Old gas (if your C12 was stored in a plastic container), air leak, lean jetting, etc. Normally needs a new top-end, but cranks are often okay.
I think it's aluminum as well. Really hope it's just top end, since I did the whole motor including low end...they only have 7.7 hours on them. I'm pretty careful w c12, try to only mix what I use. Usually doesn't sit in jug very long.
cleareforlanding 5/3/2015 12:34pm
5/3/2015 12:34pm
Matt Fisher wrote:
That's either silica (dirt) or bits of aluminum on the plug. :( Dirt would be from something like an air filter with a bad seal, torn...
That's either silica (dirt) or bits of aluminum on the plug. Sad
Dirt would be from something like an air filter with a bad seal, torn intake boot, etc. Needs a top-end and usually a new crank too.
Aluminum is usually from detonation. Old gas (if your C12 was stored in a plastic container), air leak, lean jetting, etc. Normally needs a new top-end, but cranks are often okay.
I think it's aluminum as well. Really hope it's just top end, since I did the whole motor including low end...they only have 7.7 hours on them. I'm pretty careful w c12, try to only mix what I use. Usually doesn't sit in jug very long.

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project racer 5/3/2015 2:49pm
5/3/2015 2:49pm Edited Date/Time 5/3/2015 2:50pm
Try to find the cause of the failure. Pressure test / leak down, will pin point any air leaks. Make sure the timing is correct, also.

Err to the rich side on carb settings / jetting, then work back to optimum settings.

Throwing another top end at it without some investigating may not be all it needs.
Jakes Dad
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Jakes Dad 5/3/2015 4:44pm
5/3/2015 4:44pm
Cut the threads off that plug, hacksaw around just below where the wrench goes, then you can properly read a plug. Camera flash gives it that sparkly effect looking like aluminum. Hopefully nothing too bad, don't wipe the top of piston off until you get some pics of that also.
Matt Fisher
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Matt Fisher 5/3/2015 8:18pm
5/3/2015 8:18pm
Jakes Dad wrote:
Cut the threads off that plug, hacksaw around just below where the wrench goes, then you can properly read a plug. Camera flash gives it that...
Cut the threads off that plug, hacksaw around just below where the wrench goes, then you can properly read a plug. Camera flash gives it that sparkly effect looking like aluminum. Hopefully nothing too bad, don't wipe the top of piston off until you get some pics of that also.
Excellent points; from project racer too.
I would also add- check for a burnt spot on the underside of the piston crown. Given that it wasn't running for very long, I wouldn't expect to see that, but it's more information that might help solve the cause of the problem.

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