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02 yz 250 won't start

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Cleaned carb and power valve getting spark air good still won't start

Do a compression check.  If it has decent compression, then it is most likely a fuel issue. 

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Ok it seems to have decent compression would anything else stop it from starting

Ok it seems to have decent compression would anything else stop it from starting

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A motor needs three things to run, fuel, fire, compression, and air.  If you are getting fuel, fire, and air then it is most likely compression.  One way to check to see if youre getting fuel is to spray ether into the airbox and try to start it.  if it runs for a few seconds then dies then its not getting fuel.  If it doesnt do anything then buy a compression tester.  Theyre like $10 on ebay.  even if it seems like its got good compression it could still be s litte low.

 

Also, what bike is it? I am assuming 2 stroke for some reason but if it is a 4 stroke that opens up a whole new variety of issues


Whoops thats 4 things not 3

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First of all I'd like to thank u for ur help

It is a 02 yz 250 I bought off a guy and he said top end was just rebuilt u can see all the new seals through out. Ya 2 stroke I think I will get a tester tho try that and go from there cause idk what else it could be like u said the 4 things I got them all

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Busted reed? Malfunctioning choke? Does pouring gas in the cylinder make it start? Old top end? Fouled plug? Water leak? Timing off? Pipe plugged?

You just got it, so do a top end rebuild (never trust the previous owner), clean the carb (inside, not outside), replace the air filter, put in a new spark plug and mix up some fresh gas.

Oh, and make sure that you pulled the washing plug out of your exhaust;)

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Like KTMforlife said, you need 4 things for your engine to run.

 

1. Compression

2. Fuel

3. Air

4. Correctly timed spark

 

Of those 4 things, it's almost always Fuel or Compression that is causing the issue.

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I vote for the timing.  Check to see if the key is sheared on the flywheel.

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