Hello,

I was riding my bike at the track a few weeks ago when I noticed my clutch started to slip a little bit out of some of the turns while riding.  I was having such a good time riding that I continued for a few more laps.  Next thing I know I come out of a turn and my bike boggs, dies, and would not start.  I got it home and got it to fire up but only for a few seconds and after that the bike will not start ever since.

I pulled the plug and positioned it next to my head bolt and kicked it over and it would spark.  I tested the compression with the engine cold and got about 60 psi.  I cleaned the jet and bowl out in my carb, seemed to be clean.  I have the intake off and when I twist the throttle I can see that there is fuel squirting down the intake towards the valves.  I shimmed my valves about 12 hours ago and just rechecked them again and noticed that they are slightly loose out of spec but I still think it would fire.

I'am I missing something?  You would think that with the fuel, spark, and compression that it would at least fire up for a second, more than a little backfire.  I was thinking that the heat build up from my clutch slipping could of damaged my stator, rotor, or coil.

This is a last ditch effort before I take it to the dealer.

Sounds like the typical cracked piston.  You could bore scope it, do a leak down test, or pull the head off and have a look.  60 psi is quite low even for a decomp. engine.  I believe the spec. is 90 psi.  You could even disconnect the decomp assembly and recheck the comp., that will give you a good indication if the piston is cracked.  Without the decomp. active compression should be at least 180 psi.

Yeah that was my first thought after reading some other posts on here.  That's why I did the compression test.  The manual says 65.2-109 psi at 5 kicks and that's with the engine all warmed up.  I figured with a cold engine that 60 psi was still pretty good.  I'll probably just pull the head of and visually inspect the piston.

How do I disconnect the decompression assembly?

Its crazy that the piston would just spontaneously crack like that.

Okay I see the how to disconnect the decompression assembly.   Wouldn't the compression be a lot lower that 60psi if the piston was cracked?  I can fill a little bit of pressure from the crankcase breather hose when I kick it over.

Almost all of the stock and some of the aftermarket pistons had this problem if the engine was ridden at moderate level and above.

Remove the valve cover and look at the end of the exhaust cam.  You will see a spring that adds resistance to the weights.  Remove the spring and wire the weights out.  That is the quickest way I can think of.

I'm not saying this is definitely your problem but a likely one.  You may need to go through the diagnostic tree, fuel, spark, timing, and, compression?

Does it feel normal when you kick it or is it a little easier?

Its hard to tell, it definitly still has some compression but it might be slightly easier than it was before it died on my.

I'll be pulling the head off this weekend so I will post what I find out.

Yep cracked the piston.