OldTimer

Member
Feb 3, 2005
475
0
My son and I were doing a little light trail riding today and about a half hour in, he slowed down approaching a mud hole and the bike died. I teased him about stalling it, but he said it died on it's own. "Did you turn the gas back on when you picked your bike up a few minutes ago?" He always turns it off when he drops it over, which he'd done a few minutes earlier. "Yep." I restart the bike and it dies as soon as I let of the throttle. I restart it again and notice the throttle response is REALLY sluggish. Hmm, the plug must be going or something. I turn the idle screw up about a half turn so it will idle and tell him we'll have to try to limp it on in for a closer look. As we get going down the trail again, I notice there's NO smoke and he's really laboring to keep it running. Fearing seizure, I have him kill it and pull over.
Back at camp and after the bike cools off I check the plug and compression, kick it over by hand to see if all feels right. The plug is tan, but may be carbon fouled so I put in a new one and try it... Nothing. About every fiftyith kick it will do one of those chuggy "foom" back fires and that's it. I take the new plug back out to see if she's flooded. It's dry, too dry, in fact, it doesn't seem to be getting ANY fuel. There's fuel in the carburetor, the jetts are clear, and pinky finger check tells me the reeds are still in place. Hand over the tail pipe tells me air is moving, but I can't detect any fuel in the cylinder. I hold my hand over the intake side of the carburetor to see if there's suction and it gets covered with fuel.
Any ideas what might cause this problem????

BTW - I even tried a dose of ether down the muzzle with nary a drop reaching the plug it seems.
 

OldTimer

Member
Feb 3, 2005
475
0
The carb is fine, but even if it were clogged, the ether should have reached the spark plug. It seems as though I'm not getting proper suction and I can't think any reason this could happen other than the reed valve. I'm going to take the reeds out today for a closer look, but posted here for more ideas as to what else to be looking for.
For some reason I'm all worried about crank problems, which these bikes are notorious for, but I can't imagine how that would cause these symptoms.
 

earl pittz

Uhhh...
Mar 9, 2007
63
0
That does sound alot like the reeds. If they are broken, you should get some metel reeds, they never brake. Do you have a good, fat, blue spark?
 

OldTimer

Member
Feb 3, 2005
475
0
Closer inspection revealed perfect reeds and a seized piston! :yikes:
The cylinder wall is wrecked and piston destroyed.
Now I wonder if some sort of lean condition existed during the final moments that caused the seizure or if maybe the loss of ring seal caused it to lose suction? The "thumb-over-the-spark-plug-hole" compression test seemed strong enough to move fuel through the motor.
I'll have to make sure there's plenty of flow after I make the repairs and before I start it.

BTW - Can a majorly scuffed KX65 cylinder be repaired?
 

CRazy250

Member
May 28, 2006
334
1
well how much compression did you think your thumb tester was? just because it "felt" like it has compression dosent mean its good. never do that stuff because it a generalization and things like this tend to happen because of that......but most importantly what oil ratio did you have wen the bike suddenly seized??????
 

TimberPig

Member
Jan 19, 2006
859
1
earl pittz said:
That does sound alot like the reeds. If they are broken, you should get some metel reeds, they never brake. Do you have a good, fat, blue spark?

Metal reeds have not been standard for many years, because when they do break (yes they actually do break, they aren't indestructible) they destroy the engine. On a bike as new as this one, the odds are very high, metal reeds never have and never will exist, without custom building them. Nylon/fiberglass/carbon fiber reeds also respond quicker than steel reeds, for better throttle response.
 
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