'90 KDX still not working

[1990kdx]

im still having the same problem from an earlier post. http://www.dirtrider.net/forums3/showthread.php?t=180430.

my bike is still not starting.

Reeds are perfect. got them out, dont see any cracks or damage to them, and make a good seal.

great spark still. the coil is now only a few months old, and spark plug is not fouled. creates a good spark.

im pretty sure the gas is still good, but will be getting new gas soon to double check. works fine in other 2-strokes.

cleaned the carb, and it is now perfect. all passages are cleaned, and looks great. gas runs freely through it. all jets are clear and clean.

bought a new gasket for the exhaust, and no longer has oil coming out... but there is oil in the pipe (enough to drain out), and spits from the silencer - when it runs.

Ganna be doing another compression test, right after i get my gasket for the reeds.

what is wrong with this bike??? any info would help. thanks

 

[SS109]

Not to be an old meanie but you should really keep this to the original thread so that you are not having to repost everything again and get the same answers as well.

 

[julien_d]

Agreed on keeping to the old thread. Starting a new one for the same question does nobody any good.

Could be any number of things.

Low compression, leaking main seals, timing off, carb issues (i know you said it's clean, but I'm not gonna take you at your word on that ;).

 

[dirt bike dave]

FWIW, the spark can appear OK when you test the plug on the outside of the cylinder, but still be weak under the different conditions inside the cylinder.

I suspect the spark is coming at the wrong time (sheared woodruff key?) or is too weak (bad stator?).

Remove the air filter, Get some starting fluid, spray it in and kick. If it fires, spark is probably at the right time but too weak. If it does not fire, spark timing is probably way off.

 

[omrik88]

If i may add...
you can unscrew the plastic cap that connects to the ignition coil and see if there are a good bunch of wires sticking out of the ignition cable, or only a few...well if that is the case you are getting a weak contact and might be getting a low spark...just take a sharp cutter and give it a small trim to expose the wires(don't forget to leave some spare cable to reach the plug!!!).
About the carb - take out the fuel tube where it connects to the carb and open the petcock, to be sure the fuel is getting there.
It might be good to check if the air is going through in the fuel cap.

I hope this helps.

 

[EYY]

Definitely agreed on the idea of sparkplugs seeming "ok" when tested out of the cylinder. They definitely have the ability to trick you, i've fallen victim a few times! An air leak is also a likely cause, along with all of the other factors Julien has already pointed out.

You could try removing the silencer and seeing if it starts. If it started, that would indicate a blocked muffler (quite a lot more common that you'd think).

EYY

 

[1990kdx]

EYY you were right it was the spark plug. i put a new one in 3rd kick it started. the muffle was covered with a rag. it runs better then when i boght it.