kx125 plastic restrictor/ kips tuning

[briar1989]

hi all I have a 1990 kx125 .5mm overbore fresh rebuild upon putting it back together I tore the carb holder the bike would run and I assume the kips are not right because it had no powerband or possibly because of the torn holder. now I took it back apart replaced the carb holder and reeds but I forgot the plastic restrictor now it will not even fire. I also wonder if anyone here could help with how to tune the kips system the manual has been wrong on a few things so far maybe the procedure for the kips is wrong as well.(just to clarify the diagram and instructions for replacing the clutch are not even close in the manual) any help would be greatly appreciated

[The Spanky]

That "restrictor" as you call it is called a stuffer, and it needs to be in there to maintain correct crankcase volume and primary compression.

 

The '90 KX125 uses the older KIPS design, and honestly I have no idea how to time it correctly. Sorry....

[zotis777]

How bad is the tear in the carb boot. And where, can you get a picture

[briar1989]

THE BOOT WAS TORN ABOUT AN INCH I TORE IT IN HALF WHEN REMOVING IT TO REPLACE IT BUT THERES A NEW ONE ON IT NOW. I DO NOT HAVE A PICTURE. I TOOK IT BACK APART AND PUT THE "STUFFER" BACK IN AND I STILL CANNOT GET IT TO START. ANY OTHER IDEAS? IT HAS FUEL TO THE BOWL GOOD SPARK

[briar1989]

OK SO I TESTED THE COMPRESSION IT HAS 60 ON THE GAUGE ISNT IT SUPPOSED TO HAVE LIKE 150?

[zotis777]

Yes you have low compression

[adam728]

Are you testing compression with the throttle held wide open? If performed at idle you'll get a much lower reading. If 60 psi is at WOT, then compression is much to low to run. Break a ring putting it together? Piston and rings the correct size for a 0.5mm overbore?

[The Spanky]

Are you testing compression with the throttle held wide open? If performed at idle you'll get a much lower reading. If 60 psi is at WOT, then compression is much to low to run. Break a ring putting it together? Piston and rings the correct size for a 0.5mm overbore?

 

 

This. To do a compression test you have to hold the throttle wide open, and kick until the gauge stops moving.

 

An engine with only 60 psi static compression will most certainly not  run.

[briar1989]

STILL THE SAME GONNA GET A NOTHER RING AND GASKET SET IN A FEW DAYS WE WILL SEE WHAT HAPPENS

[briar1989]

OK SO I RE DID THE COMPRESSION TEST AS ADAM728 SUGGESTED AND THE GAUGE STOPPED AT 120 BUT THIS SEEMS LIKE IT WOULD BE A FLAWED RESULT TO ME. MAYBE I AM JUST NOT FRAMILIAR ENOUGH WITH 2 STROKE ENGINES BUT SHOULDNT IT HAVE THE SAME COMPRESSION WITH ONE KICK AS IT DOES THREE?

[adam728]

No. Typically takes 5-10 kicks to top out the gauge. There's air volume in the gauge hose that must be compressed as well.

[briar1989]

ok that makes sense... so I have good spark even found the recommended ngk plug, compression and fuel to the carb bowl but the bike still wont run I am at a total loss at this point it just doesn't make sense to me...once again just to reiterate 120lbgs compression new carb boot fresh fuel oil mix pull the plug out of the bottom of the carb(needle access) fuel dumps out take the carb off I can see that there is fuel on the reeds... any ideas now guys? any help is greatly appreciated

[Jeekinz]

Weak spark or big fat spark?

 

My 94 KX coil went but it still produced a weak spark.