Motorcycle Repair: Have spark & fuel but wont start, air filtration, starter fluid

Question
Hey Chris, After reading several of your answers to similar questions I think my problem might be compression? Heres the story...My daughters quad (2004 kasea 150) just up and quit on her while she was riding in the desert. She had gas and the starter cranks but after checking the spark plug I noticed the spark was weak at best. I installed a new plug with no luck. Next put in a new coil...no luck. So I ordered and installed a new cdi unit and rectifier. I now have a good steady spark but it still wont start. So I figure must be fuel? I checked fuel lines, no problems, tried starter fluid no luck, took the carb off. jets looked clean(clear round holes both idle & main) cleaned everything even though it wasn’t dirty, put it back on and it cranks but will not even sputter. If I open the throttle it sounds even weaker. If throttle is closed you can hear the carb sucking air (I have removed the air filter)when throttle is opened it does not seem to suck air? Anyways Im at a loss. Any ideas would be greatly appreciated. Thanks, Bill


Answer
Hi Bill.

 A couple of years ago, I was going round and round with an issue that one of our hero's in Iraq was dealing with.  He was in the maintainence platoon for a unit that had a motorcycle platoon and the bike kept getting into trouble.  The problem he was having doesn't matter here, but the reason that I mention it is because you say that your daughter rides it in the desert riding area near you.  The one thing that he mentioned is that they change the air filters and oil/oil filters a lot because of SAND INTRUSION.

Now the area where you are at may not have the insidious kind of sand that is common in the Middle East, but sand, when it gets into things, and it will in areas like that, can build up and cause real problems with the engine, air filtration as well as the electrical (gets into connectors).

Have you changed the oil and filter recently?  How about the air filter?  If sand got into the engine through any of a few different ways, then it could be gumming things up.

Make sure that the valves and valve seals are set right and in good condition and then check your compression.
If it is low, then flush the engine and change the oil and filter, and then check your compression again.
 If it is still low, then you will, likely, need to do some deep work in the engine to repair it.

Good luck and ride safe.
FALCON