Spark + Gas + Compression = DEAD?

4 replies to this topic
  • Yamahafan

Posted April 19, 2005 - 11:38 AM


The bike ran great last fall. I had a 262 kit installed, new timing chain and the valves reshimmed after the riding season, but did not try to start the bike until this spring after I perfomed my winter maintenance. This spring my bike won't start at all.

Spark - I performed a spark test with the plug against a bolt on the engine block. I saw a strong, blue spark using a brand new spark plug. I am using an iCat. My hour meter is advancing as we kick the bike. I assume I would get spark if the kill switch were malfunctioning.

Gas - I put in brand new BP Amoco 93 octane. Nothing. My mechanic removed the carb and sprayed starter fluid directly into the cylinder. He said it should have started and run like a scalded cat, but nothing.

Compression - compression is about 30 pounds after 3 or 4 kicks. I am running a 2003 YZF exhaust cam with decomp.

Timing - The timing was checked and rechecked by the mechanic.

We are absolutely stumped. We are going to start working through the electrical system next. ANY THOUGHTS?

  • ISBB

Posted April 19, 2005 - 01:58 PM


i thought the compression was in the hundreds???

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  • DesertWR

Posted April 19, 2005 - 02:18 PM


You have gas & spark-How about oxygen??

  • Frostbite

Posted April 19, 2005 - 03:00 PM


If your compression is only 30 psi, you have problems.

  • new2blu

Posted April 19, 2005 - 05:03 PM


If your compression is only 30 psi, you have problems.

You have compression problems!
Remove valve cover, put engine on TDC on the compression stroke and see if the cams are in their correct position.
I'm not sure if the WR250 has auto compression release; but that could be sticking causing low compression.


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