Exhuast is melting air filter box

57 replies to this topic
  • RPS444

Posted March 24, 2015 - 12:17 PM


2005 yz450f. The header glows red when idling which I have heard is normal but the abnormal part is that my whole exhaust system starts to glow red after less then a minute of idle. Something else that I noticed is that it has a small anti freeze leak out of the weep hole. Is this the main problem for overheating the exhaust pipe? 

  • 03yzf450-kuke

Posted March 24, 2015 - 03:30 PM


Normal glow I'm pretty sure only just wraps the bend. I'm no expert but sounds to me like your way too lean on idle. Also leaking out the weephole means your impeller seal is leaking

  • guntoter535

Posted March 25, 2015 - 03:00 PM


If your impeller seal is leaking and its getting that hot, your water pump is probably going out

  • 03yzf450-kuke

Posted March 26, 2015 - 02:40 AM


I would pull the carb and give it a good clean. Also look for air leaks around carb boot.

  • RPS444

Posted March 26, 2015 - 06:23 AM


Carb was cleaned thoroughly. It has a PMB spark arrestor on it and I wasn't sure if that means I need to mess with the jet settings which are still stock. Another issue that I'm sure isn't helping is that I think all the packing is gone from the silencer. Would that cause the popping and backfiring I hear along with the heat in the pipe? I just bought this bike and now I'm discovering some of the problems.

  • 03yzf450-kuke

Posted March 26, 2015 - 11:38 AM


Have you checked your intake boot for leaks? Spray some carb cleaner around boot while running and see rpms increase

  • WilfulLemar20

Posted March 28, 2015 - 08:29 AM


I would move needle up a notch or 2 and it's best to get easy to access air fuel screw I just bought an 04 yz450f and the carb is a nightmare I am really considering trying this kit http://www.ecotrons.com/

  • 03yzf450-kuke

Posted March 28, 2015 - 03:31 PM


It would be in the pilot circuit if the problem does in fact lie in the carb since its happening at idle. It is normal for header to glow after idling for a couple minutes but not to the mid pipe in under a minute that totally sounds like a clogged pilot jet or air leak somewhere

  • RPS444

Posted March 30, 2015 - 05:25 AM


Thanks everyone. We are going to check out the water pump tonight to see if the leak is from a seal or bad impeller.

  • RPS444

Posted March 31, 2015 - 11:09 AM


Should there be any play in the impeller when you twist by hand or should it be tight?

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  • grayracer513

Posted March 31, 2015 - 11:21 AM


Yes.  The impeller is driven by a flat tab on the end of the shaft which fits a socket in the end of the balancer drive gear.  You can normally rotate them about 30 degrees or so by hand.


Read: http://www.thumperta...0-coolant-leak/

  • guntoter535

Posted March 31, 2015 - 01:59 PM


There is a double seal on the impeller. It is usually the second seal that goes bad

  • grayracer513

Posted March 31, 2015 - 02:17 PM


There are two seals because the shaft passes between two volumes containing two fluids that need to be contained, coolant in the water pump, and oil in the primary drive case.  One seal controls oil, and the other water.  You don't need to replace the oil seal if only coolant is leaking, but as you read the link I posted, you will see that the only correct method of removing the impeller form the shaft involves the removal of the right crankcase cover anyway, and thus exposes both seals to ready removal, as well as the shaft and bearing for inspection.  The two seals together are quite inexpensive, so I always replace them as a pair.

  • RPS444

Posted April 01, 2015 - 05:13 AM


Thank you! The first seal was bad and the second seal will be replaced as well. My only concern is that it won't fix the mid pipe turning red hot less then a minute at idle. The muffler has zero packing in it so I'm going to replace it but I still can't figure out what is causing it to heat up so quickly that it started melting the air filter box right away.

  • guntoter535

Posted April 01, 2015 - 07:12 AM


Lean jetting, clogged slow jet extra air getting into fuel circuit or exhaust. Check all rubber gaskets that may have deteriorated causing excess air

  • grayracer513

Posted April 01, 2015 - 09:53 AM


My only concern is that it won't fix the mid pipe turning red hot less then a minute at idle.

It won't.

  • RPS444

Posted April 01, 2015 - 10:58 AM


Yea it's really a bummer. I'm thinking it may be time to cut losses and dump it, I've tried everything people have recommended. I appreciate all the help.

  • 03yzf450-kuke

Posted April 01, 2015 - 11:27 AM


Keep looking ...... Check for air leaks everywhere.... Have you checked the hot start?

  • 03yzf450-kuke

Posted April 01, 2015 - 11:31 AM


How did you go about looking for air leaks?

  • 03yzf450-kuke

Posted April 01, 2015 - 11:35 AM


It is most likely a simple problem just needs to be found. You should be spraying carb clean around intake boot and try pulling the hot start and plugging the air passage and see if it makes any difference

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