Yay another rebuild after 3 or 4 hours..

[KxOneHundred]

Long story short Ive been fouling plugs don't know if too lean or what but ordered a jd jet kit this time, thank God the cylinder is fine I just had it replated. Getting a Namura not spending double again on a wiseco,Just wanted to give yall a heads up learn to jet and don't be a &%$#@!ing retard like me and keep running your dirt bike after you've fouled 4 plugs in a few hours. I'm an idiot. This piston was clearly burnt running to lean I assume right?

[vossman23]

Ouch.

[kxrob]

plug looks fine , i think you got other issues , i wouldn't go with a namura piston , they don't seem to have a good reputation

[KxOneHundred]

Ouch.

I've thrown so much cash at this bike recently ugh, bought it for 1000$, cylinder replated w/power valve service 280$+90$,new grips and levers, 2 new Dunlop mx52s I jus bought, repacked the silencer, carb rebuild kit, 4 hours ago it had a new wiseco in it, new radiator hoses, new rental golden chain and sprocket kit, and a few other things. Definitely can't give up on it now..

[KxOneHundred]

plug looks fine , i think you got other issues , i wouldn't go with a namura piston , they don't seem to have a good reputation

Any idea what it is then? The cylinder is crisp I'm pritty sure I'm running lean, even the rings melted on the piston..

[vossman23]

Plug doesnt show lean, are you sure that was not from scraping on the cylinder edge (looks like exhaust ports) at like 10 or 11 o'clock in your pic? The cylinder itself doesnt seem to be bad at all from the one pic. What do the other sides of the piston look like?

Edited November 6, 2018 by vossman23

[Motox367]

Major case of cold seize right there . Or forgot to mix gas , you ride it on roads by chance?

[turbo dan]

You can be lean on the pilot/needle, rich on the main.  That'll do it.  Plug won't show lean running like that.

Wiseco is not my favorite piston in a small bore but it is infinitely better than a Namura.  I would recommend an OE piston from a place like partshark. 

[FaceDeAce]

Major case of cold seize right there . Or forgot to mix gas , you ride it on roads by chance?

 

+1 on this. That sure looks like a cold seize to me too.

 

The spark plug looks perfect! Jetting is fine. Maybe slightly rich, but fine.

 

Put an oem cast piston in and be done. Stay away from forged.

 

[mlatour]

When you had the cylinder replated, did you have it matched to a piston?

Did you measure piston to cylinder clearance or ring end gap?

What premix ratio?

Riding in cold late fall ambiant temps on stock jetting?

What is your cold engine starting / warm up method?

Do you ride on roads / sustained wide-open throttle?

 

Save now with a Namura and it may cost you another cylinder replate or bottom end.

A questionable quality piston in this same situation may have taken out the rest of the engine as it failed.

 

Investigate before simply slapping in a new piston as to what the exact cause is:

low float level, insuficient fuel flow, crank seal / air leak, debris past air filter, improper clearances, or rather rider/mechanic error

Edited November 7, 2018 by mlatour

[KxOneHundred]

Major case of cold seize right there . Or forgot to mix gas , you ride it on roads by chance?

Yes sir I ride nothing but the streets sadly I'm in an urban area with no forests or anything

[KxOneHundred]

When you had the cylinder replated, did you have it matched to a piston?
Did you measure piston to cylinder clearance or ring end gap?
What premix ratio?
Riding in cold late fall ambiant temps on stock jetting?
What is your cold engine starting / warm up method?
Do you ride on roads / sustained wide-open throttle?
 
Save now with a Namura and it may cost you another cylinder replate or bottom end.
A questionable quality piston in this same situation may have taken out the rest of the engine as it failed.
 
Investigate before simply slapping in a new piston as to what the exact cause is:
low float level, insuficient fuel flow, crank seal / air leak, debris past air filter, improper clearances, or rather rider/mechanic error

1.Yes sir had it replated to 52.50 same spec as the piston I sent in
2.I'm not going to lie I didn't measure the ring end Gap
3.The premix ratio at first I did was 32 to 1 then I switched to 40 to 1
4.I'm in Miami so it's quite hot over here
5.My warm up method is a let it warm up for a good 5 or 10 minutes then I putt around, and then I punch it
6. And yes I'm in Miami so there's not really much options so I ride nothing but the road

 
+1 on this. That sure looks like a cold seize to me too.
 
The spark plug looks perfect! Jetting is fine. Maybe slightly rich, but fine.
 
Put an oem cast piston in and be done. Stay away from forged.
 

Sadly I already ordered a Namura kit it's only going to be temporary though until I get it jetted right

[KxOneHundred]

Plug doesnt show lean, are you sure that was not from scraping on the cylinder edge (looks like exhaust ports) at like 10 or 11 o'clock in your pic? The cylinder itself doesnt seem to be bad at all from the one pic. What do the other sides of the piston look like?

Here's both sides check it out

[KxOneHundred]

Also I just want to say, I love the amount of support I get from you guys this forum is awesome[emoji16]

[vossman23]

1 minute ago, KxOneHundred said:

Also I just want to say, I love the amount of support I get from you guys this forum is awesome

On that comment I'm gonna say I'm out and leave it to the smarter guys. Cold sieze sounds about right as most of the damage was done on the exhaust side of the piston, would of heated up fastest but dang that thing is munched. Maybe someone in Fla can help you out when you get ready to put it back together. Good Luck KX100.

[KxOneHundred]

On that comment I'm gonna say I'm out and leave it to the smarter guys. Cold sieze sounds about right as most of the damage was done on the exhaust side of the piston, would of heated up fastest but dang that thing is munched. Maybe someone in Fla can help you out when you get ready to put it back together. Good Luck KX100.

Thanks brother!

[mlatour]

IMO the biggest contributor to the damage is the sustained high rpms of street riding.

In stock form, these engines are jetted for best throttle response and acceleration, meaning on the verge of lean.

Sustained WOT down long stretches requires richer settings (mostly the main jet) which oppositely would be too rich for typical MX track usage.

 

 

[KxOneHundred]

IMO the biggest contributor to the damage is the sustained high rpms of street riding.

In stock form, these engines are jetted for best throttle response and acceleration, meaning on the verge of lean.

Sustained WOT down long stretches requires richer settings (mostly the main jet) which oppositely would be too rich for typical MX track usage.

 

 

Damn, makes sense though, also when I'd give it full throttle it would bog.. Hopefully this jd jet kit helps out

 

[mlatour]

Whatever settings that kit recommends it is likely for motocross track in mind, not road racing.  

Go up at least 2 sizes on the main jet if you insist on riding it in such fashion but even then you are risking another seizure.

 

Switching to 32:1 wouldn't hurt either.

 

IMO you are lucky to even get 3-4 hours out of it each time,

this is obviously the wrong type of bike for your needs.

[KxOneHundred]

Whatever settings that kit recommends it is likely for motocross track in mind, not road racing.  
Go up at least 2 sizes on the main jet if you insist on riding it in such fashion but even then you are risking another seizure.
 
Switching to 32:1 wouldn't hurt either.
 
IMO you are lucky to even get 3-4 hours out of it each time,
this is obviously the wrong type of bike for your needs.

Damn I understand thanks for explaining, guess I gotta take it a bit easier and stay on 32 :1, definitely rejet and find me some damn trails!