Blown top end?

I was riding my 05 125sx today when I had a big problem. I was at just about the top speed for a minute then slowed down. When I stopped I realized that there was way too much smoke coming out of the pipe and it smelled burnt. It started back up fine but still smelled bad. What could this problem be?

Look at your mixture, it could just be that your running really rich. I had the same exact thing happen with my ktm but then I found out it was only from a rich mixture. I could be wrong, maybe your top end is blown, that coolant would also cause a lot of smoke. Check it out man, I hope it's not a blown top end.

Look at your mixture, it could just be that your running really rich. I had the same exact thing happen with my ktm but then I found out it was only from a rich mixture. I could be wrong, maybe your top end is blown, that coolant would also cause a lot of smoke. Check it out man, I hope it's not a blown top end.

It's definitely not just rich. I've had it for almost a year with no problems.

Possibly blown head gasket.....did you check your coolant?

I'm guessing you blew a head gasket then, coolant is being burned in the cylinder. That's my best bet. What color smoke?

Haha never mind someone just said the same thing

Thanks guys the head gasket makes a lot of sense. I'm probably gonna start looking into it tomorrow and I'll do a compression test. Oh and the smoke was white if that helps.

Thanks guys the head gasket makes a lot of sense. I'm probably gonna start looking into it tomorrow and I'll do a compression test. Oh and the smoke was white if that helps.

 

Yup, that's a sign of a blown head gasket......

Yep.

Ok so I did a compression test and got between 120 and 135 (varied each time). Last time I ran one it had 150. Is this a sign my top end is beginning to wear too?

Probably lower on compression due to the blown gasket.

But you should probably put in a new top end as preventative maintenance. It sounds like its been a while since it was done.

I pulled the head and pretty sure is was the head gasket, so I'm ordering new ones (the outer gasket too).  I don't think I'm gonna rebuild the engine just yet.  I don't really put that many hours on it or race it so I don't think it's worth it yet.  I'll make sure I keep and eye on the compression though.

Was the plug wet? Do you see any bubbles in the radiator when kicking it over?

Edited by terdog

Was the plug wet? Do you see any bubbles in the radiator when kicking it over?

Yes the plug was very wet. I didn't think to look for bubbles and now it's all apart so I can't answer that question. I'll put up a picture of the head gasket soon.

Here's a picture of the head gasket. I don't know if you can tell, but it is a little shredded on the left and right side. I don't know if this is enough to cause a leak or not.  Of course rockymountain sent the wrong size gasket in the mail, so I haven't been able to put it backtogether yet.headgasket_zps2ebd4acf.jpg

 

 

But you should probably put in a new top end as preventative maintenance. It sounds like its been a while since it was done. 

Or, you can break it down, then measure the parts for wear and replace what it needed. Your ring end gap might be ok. I will be trying out the NAMURA rings in my sons 2000 125 EXC. We pulled the pipe and looked at the exhaust side of the piston - not a single mark on it.

 

RM sent you the wrong gaskets? I never have a problem with them.

they sent the wrong one or you ordered the wrong one ?  and i think its called a oring

Edited by harryhandshake

While you have it apart have the head and cylinder surfaces checked.  The o ring only seals the water jackets not really a head gasket in the form of sealing the 2 surfaces for compression.   The cylinder to head junction is a dynamic seal that can warp if over heated causing o ring failure immediately.  You can just replace the o ring and try it but it failed for a reason. 

It is the o ring not the head gasket. The head gasket would have nothing to do with coolant getting into the cylinder but the o ring does. I don't think the mistake was rm's fault. The number on the bag was correct but the o ring wad not the right size. They are sending mr a new one free. Should I just take it to a shop and have it looked over? I wad hoping not to have to do that but will if it comes down to it. It sounds like the problem is deeper than I thought.

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