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1981 XL500s won't start when engine warm

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My 1981 Honda XL500s starts and runs fine but after warming up and shutting down I cannot restart the engine.  I checked the spark plug and am getting good spark, got gas, wants to go but nothing...  after sitting for a day starts up first kick normally.  Cannot figure this one out!  Please help, I have a trip coming up this weekend and don't want to miss out!

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i had 81 xr500 that was like that - had to let it cool down for about 15 mins.

have you tried running a colder plug - D9EA ?

what you could try is - when it gets hot and wont start - swap out the plug for another D8EA and see if it will start

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When you start it cold what do you do?

  • How much choke?
  • Do you open the throttle at all?

Should need little choke unless weather really cold and no throttle at all. If you have to deviate from that it might tell us something.

 

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My usual start sequence I open the choke all the way, normally no throttle but recently tried with throttle seemed to help a bit.

Edited by FreeBird88

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  Few things to check

  Valve clearance..as the engine warms up the parts expand and if the clearance is marginal tight on either valve you will lose compression making starting difficult.

  4Ts  start best when the mixture is rich when the engine is cold and inversely they like the mixture to be slightly lean when the engine is warm. If you have a worn needle jet or jet needle the mixture stays slightly rich when warm making starting difficult.

  The 500 XL500s stator has a slow and high speed coil.If the slow speed coil is starting to fail you will still get a spark just not enough to make it run.

  Check the resistance of the stator coils as per your manual.You can also check for spark strength by checking to see if the spark will jump a 8 mm gap.

  Check your spark plug cap while you are there  should be 5000 ohms or very close.If you have no reading on your meter get a new one for sure. 

Edited by nsman
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