Maintenance & Technical > KX500 Original

Toasted engine?

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Hogwylde:
I think I toasted my engine.  I was doing pretty good in a race last month when all the sudden, I notice I'm loosing power and this thing is getting HOT!!  I pull over to check and see if I've broken a radiator hose or something.  Nope, I get a geyser of hot water out of the radiator cap.  All I can think of is a dirty carb problem.  All I've had time to do since then is pull the carb and clean it and check to see that the impeller on the H2O pump didn't come off or some other pump problem.  

I managed to get it started yesterday after putting the cleaned carb on and fresh coolant in it.  Man, it sounded SICK!  Kinda made a moaning sound and wouldn't rev.....and it STILL got really hot in only the minute I was able to keep it running.  It feels like it's got good compression.

I've not had time to get into the engine to start checking things but I was wondering if I might be looking for a melted down topend, missing some reed pedals, or looking for a power valve stuck in the open position, or should I be looking for some OTHER problem?

I pretty much figure I'm done racing for this season, but if anyone thinks this might be a cheap and simple fix, I'm all ears.

alan:
I always go to the plug first! If you have had some kind of melt down the plug will generally tell the story!


Alan

hoopty:
Sounds like you sucked a petal off one of the reeds.

Hogwylde:
Plug was the first thing I checked.  It had a little build up of some black carbon, but no signs of pre-ignition or detonation or melted bits of aluminum attached.  Guess that's a good sign.  The plug was replaced before I attemped to re-start the other day.  

Thanks for the input....I'll pull the reed cage and check it tonight!

Hogwylde:
Just a follow up to this post.  Now that the racing season is over....I've finally had some time to figure out what's wrong.  Long story short.......shearing the woodruff key lets the flywheel move out of position and REALLY screws up the timing.  Now that it's fixed, she's just as mean and nasty as always.  Can't wait till next year to get racing again!!

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