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I started up my bike (a 2009 kx250f) and after 3-4 min of idling it got like that. Its really scaring me and i dont want my bike to blow up so is this something i should get checked? ImageUploadedByThumper Talk1382905707.396183.jpg

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William, do you think that he may be running a little hot? Maybe jetted too lean? Shouldn't look like that after idling 3-4 minutes. My 09 can idle for 10 minutes and my pipe doesn't look like that.

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William, do you think that he may be running a little hot? Maybe jetted too lean? Shouldn't look like that after idling 3-4 minutes. My 09 can idle for 10 minutes and my pipe doesn't look like that.

 

I think the question is, are you jetted too rich? Lol. Really though, its normal. Especially with a Ti pipe.

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I think the question is, are you jetted too rich? Lol. Really though, its normal. Especially with a Ti pipe.

 

So, you're saying a "rich" fuel/air mixture will burn hotter than "lean"?

 

 

I agree, it is normal to an extent and probably isn't going to harm your bike in any way.

 

OP, does your bike "pop" or backfire a lot?

Edited by NthoozEist

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I agree it's normal after several minutes especially with a Ti pipe, however I have found on two KXFs of my own and other TTers that properly sealing the head pipe eliminated this, as well at the popping on decel that accompanied the cherry red pipe in those cases. Good question above. Is it popping?

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I agree it's normal after several minutes especially with a Ti pipe, however I have found on two KXFs of my own and other TTers that properly sealing the head pipe eliminated this, as well at the popping on decel that accompanied the cherry red pipe in those cases. Good question above. Is it popping?

 

Thanks for the responses everyone, I am the newbie team mechanic for my son's bike we are discussing here.

 

I don't believe it is popping on deceleration but I'll pay closer attention next time he rides.  It does seem to have a bit of a stutter off idle in neutral.

 

I'm planning on pulling the plug to check the coloring and adjusting the fuel mixture screw accordingly, looking for leaks around the carb boots and checking the torque on the head pipe bolts.

 

I did check the engine coolant and it is flowing well through the radiator under the filler cap.  I was thinking of flushing and replacing it though as I have no idea when this was last done.

 

Does this seem like a good starting point?

 

Sorry for the newbie questions but my son and I are new to working on bikes and want to do/learn as much as possible ourselves.

 

Edit: one more thing that might be related, it seems to dump a decent amount of gas from the overflow hose but I'm thinking this is just the floats needing adjusted?

 

-J

Edited by McJohn

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Thanks for the responses everyone, I am the newbie team mechanic for my son's bike we are discussing here.

 

I don't believe it is popping on deceleration but I'll pay closer attention next time he rides.  It does seem to have a bit of a stutter off idle in neutral.

 

I'm planning on pulling the plug to check the coloring and adjusting the fuel mixture screw accordingly, looking for leaks around the carb boots and checking the torque on the head pipe bolts.

 

I did check the engine coolant and it is flowing well through the radiator under the filler cap.  I was thinking of flushing and replacing it though as I have no idea when this was last done.

 

Does this seem like a good starting point?

 

Sorry for the newbie questions but my son and I are new to working on bikes and want to do/learn as much as possible ourselves.

 

Edit: one more thing that might be related, it seems to dump a decent amount of gas from the overflow hose but I'm thinking this is just the floats needing adjusted?

 

-J

 

No problem with any questions.  Before just re-torquing the head pipe, keep in mind those nuts are not very high torque (15 ft-lb) and they should be torqued evenly.  The only way to re-seal the system is to back off the fasteners and re-torque in the proper order, so leave the silencer and mid pipe secure, back off on the clamp between the mid pipe and head pipe, back off on the nuts to the head pipe.  Once you back everything off, first torque the head pipe holder nuts, then the mid pipe clamp.  Order is important.  

 

There is a copper gasket that goes between the head pipe and head.  You can buy a new one very cheap.  If taking tension off and reassembly doesn't do anything, then get a new one of those.  Or, just get a new one to begin with.  

 

The reason the header gets superheated in an unsealed pipe is because unspent gasoline mixes with air in the hot head pipe and burns.  Often this ignition can be heard as popping.  Either way, before you do any carb adjustment, make sure your exhaust system is sealed.  If it is not, your bike won't run optimally.

 

If your head pipe still glows red after you ensure it is totally sealed, meaning you bought a new gasket and re-assembled in order, I would be surprised.  But, it isn't hurting your motor in any way.

 

If you want to monitor the heat in the cylinder, which is unrelated to the heat in the pipe, go to an auto shop and pick up a temp strip.  They stick right on the cylinder.  

 

Kudos for being your son's chief mechanic  :thumbsup: very rewarding job.

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Awesome.  I have a torque wrench so I'll dust it off and get to work.

 

Thanks!

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I finally got around to looking at the bike and found it has no crush gasket at all and the jetting seems like it was never changed from stock.  The main jet is 182 and the pilot is 40.  I'm going to keep the main jet as-is and have ordered a 42 and 45 pilot jet (for summer and winter in GA) and the crush gasket. FMF jetting center recommends the following (they told me these settings are for 70 degree SoCal weather and to adjust accordingly):

  • Main Jet 180
  • Pilot Jet  42
  • Needle   NCYS
  • Needle Position  4TH
  • Air/Fuel Screw 2 1/2

I don't know what needle I have but am assuming it's stock and am planning on using it for now. 

 

For winter in GA I'm going to start with the 45 pilot, leave the main jet at 182 and bump the needle position down one (this will richen it right?).   I'm also installing a trackside air fuel mixture screw so I can adjust the fuel mixture more easily (will set to 2 turns out and start from there). 

 

Any suggestions are appreciated.

Edited by McJohn

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The only time I have ever had the pipe glow like that at idle was on a bike running very lean due to air leaks.

 

If you have the bike standing and reving it, it will glow like that.   

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I finally got around to looking at the bike and found it has no crush gasket at all and the jetting seems like it was never changed from stock.  The main jet is 182 and the pilot is 40.  I'm going to keep the main jet as-is and have ordered a 42 and 45 pilot jet (for summer and winter in GA) and the crush gasket. FMF jetting center recommends the following (they told me these settings are for 70 degree SoCal weather and to adjust accordingly):

  • Main Jet 180
  • Pilot Jet  42
  • Needle   NCYS
  • Needle Position  4TH
  • Air/Fuel Screw 2 1/2
I don't know what needle I have but am assuming it's stock and am planning on using it for now. 

 

For winter in GA I'm going to start with the 45 pilot, leave the main jet at 182 and bump the needle position down one (this will richen it right?).   I'm also installing a trackside air fuel mixture screw so I can adjust the fuel mixture more easily (will set to 2 turns out and start from there). 

 

Any suggestions are appreciated.

The gasket is copper and sometimes gets stuck in the head. If the exhaust outlet looks like copper, the old gasket is in there and must come out. If you are sure there is no gasket in there just replace it before you make any jetting changes. The exhaust has to be put back on in order. Finger tight on the muffler and midpipe support first, then finger tight on the head pipe. Then torque the muffler and mid-pipe to the frame, then torque the head pipe to the head, then torque the mid-pipe clamp. Let us know if it still glows as quickly. Also evaluate how it runs before messing with jetting.

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