98' yz 400f

7 replies to this topic
  • RF1

Posted October 06, 2005 - 03:40 PM


I just installed a new head gasket on my '98 yz400. It overheated due to the radiator leaking. I got the radiator repaired at a radiator shop. I started the bike today and it is overheating, the choke has to be on in order for it to run when I take the choke off I have to keep reving the bike and it pops, flames out of the exhaust, pipe turns cherry red. Any suggestions? Maybe I installed the wrong headgasket?

  • 642MX

Posted October 06, 2005 - 04:27 PM


Your running problem is a restricted pilot jet. Your overheating is probably due to you running the bike without riding the bike. Clean your carb and go ride it, get some air thru your radiators.

  • RF1

Posted October 06, 2005 - 04:33 PM


Thanks, I'll try that and I forgot to mention coolant was leaking out of the overflow tube.

  • phat_450f

Posted October 06, 2005 - 04:43 PM


yeah i would definetly say as for keeping your bike rev'd to keep it running is a carb adjustment. There are no fans on these bikes so 642 is right keep movment on the bike. You might also want to try a new radiator cap. Did you use sealant on the gasket you might have clogged one of the coolant ports with sealant. If you have a manual for the bike go towards the back most manuals have troubleshooting sections in it. Just look up overheating and it will give you multiple things to check. Keep us posted on what you are coming across.

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  • Pincushion

Posted October 06, 2005 - 05:51 PM


look for an air leak first. Did you use a new crush washer where the header meets the head? All 4XX bikes will overheat if left at idle for a few minutes.

  • RF1

Posted October 09, 2005 - 01:06 PM


Regarding restricted pilot jet should I replace it or soak it in carb cleaner?

  • Chris_from_Oz

Posted October 10, 2005 - 06:17 AM


Could the problem be totally unrelated to your original head gasket issue? It sounds like the carb' slide is in backwards. Did you have the carb' apart at all?

  • 642MX

Posted October 10, 2005 - 04:02 PM


Regarding restricted pilot jet should I replace it or soak it in carb cleaner?

Spray some carb cleaner thru it, then blow it out with compressed air. :banghead:

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