kx450 help needed

[chumbilly1]

Yesterday 2011 kx 450 gave it up. Acted like it was flooded. Rolled to a stop, bike stalls. Kicked for 1hour plus. Finally restarted. sounded OK. Idled, no knocks or bad noises. Bike went 35 feet and stalled again. No start. I noticed it blowing oil vapor and steam out crankcase overflow/vent when moving. Temps were in the 70s and snow was thick. Bikes were getting worked to say the least. Anyone have any good ideas. Access to area is horrible and terrain is gnarly to say the least. any ideas are appreciated. We are thinking going back in tomorrow on foot with several bodies,300' of rope, pullies etc. Be really nice if the damn thing would go out under its own power. I have been waiting for a situation like this. The capabilities of these machines with the right rider really lend themselves to hard recoveries. IMHO

 

[Rush44]

Sounds electrical. I remember a KX that had a similar issue. I used to own a 11 KX450F and so did a few of my buddies early on (it was my 2nd bike). If it was a wet day it could be as simple as a cable that is grounding out with the extra water so check the connections around your CDI box... otherwise your stator is a good place to start.

Just for giggles you might want to pull your injector clip and make sure it's free of moisture and connected tight. If you have any accessories make sure to disconnect them.

 

[chumbilly1]

Thanks Rush. Didn't unplug injector. However we did check all connections to pump. In your experience, if the crankcase oil gets contaminated with fuel and overfills will it blow oil and vapor out vent tube?

 

[Rush44]

Vapor is normal to come out of the vent tube. It should do that and expel air all the time. If oil is coming out then yes, it's probably overfilled from either moisture or fuel add, but neither should result in the problem you currently have.

 

[Ausm7499]

Had my 12 KX450 have a similar failure last season. I could get it to run by having a buddy tow me but it was blowing smoke out the crank breather. Towed it to the pickup tore the top end off that night to find a split piston. I would put money on it that's what's wrong with yours. $175 for a top end kit and I never had another problem with the bike.

 

[dooman92]

Thanks Rush. Didn't unplug injector. However we did check all connections to pump. In your experience, if the crankcase oil gets contaminated with fuel and overfills will it blow oil and vapor out vent tube?

If the bike was running real warm fuel dilution in the oil is less likely. But, if the oil is severely diluted with fuel the mixture will wash the cylinder wall of oil and reducing compression and increase blow bye. The blow bye would slightly increase crankcase pressure and be expelled via the crankcase breather tube. Oil that is severely diluted with gas will also result in hard starting due to the reduced compression.

 

[chumbilly1]

Thanks for the input everyone. Really hoping it isn't a damaged piston. Bike had a new crankworks crank and vertex hi-comp piston somewhat recently. One thing I just thought of is the fact that owner was probably running low viscosity oil when temps were cold and now they are not. You think the oil weight could have come into play?

 

[dooman92]

Chumbilly, again probably a long shot if the bike was running really warm. But, thin low viscosity oil would be more susceptible to fuel dilution. If it is fuel dilution reducing compression, some oil squirted in the cylinder would raise compression improving starting. It would be interesting to check compression before and after adding the oil to the cylinder? Did it run long enough with diluted oil, if diluted, to accelerate cylinder/ring wear? I would think it would take hours for enough wear to impact starting/running.

I have repaired autos operated in cold climates (short distances)that never get warm and eventually start hard because of diluted oil. In most cases changing the oil fixed the problem.

Please let us know what fixes it..

 

[portgrinder]

if you have things coming out of your crankcase vent you got issues. time to tear it apart.

 

[Rush44]

if you have things coming out of your crankcase vent you got issues. time to tear it apart.

Vapor, white discharge (goo) from frothy oil, and regular oil are all things that CAN come out of the crankcase vent during normal operation of the bike. Yes, any oil discharge and something isn't running optimal (like crankcase isn't fully warm and you get some goo, you overfilled the oil, you've added volume from moisture via condensation and lack of temps to burn off the vapor) but that doesn't mean it's time to tear the bike apart. No need to freak the guy out. Start simple and eliminate the easy things... electrical has always been something I've had to deal with. After all, I used to own several Arctic Cats.

 

[chumbilly1]

We are going in on Tues. when weather improves to try to recover bike. I will keep you all posted on what happens. Thanks again

 

[chumbilly1]

Well bike is out. Quite the adventure to say the least. appears to be a cracked piston. Oil was not to contaminated(no water or fuel, just dark) has spark and tried new fuel pump. When inspecting piston through plug hole you can see a clean line running inline with wristpin, and when kicking over it is leaking compression out of crankcase breather, lots of it. Good reminder to freshen these things up regularly!

 

[dooman92]

Chumbilly, did you tow it out upright or lay it down? Tow with a sled or other bike? Any pointers to pass on? Thanks

 

[chumbilly1]

Conditions didn't allow use of sleds or other bikes. We went in on skiis/skins as snowshoes. Brought 200 feet of static line and a bunch of micro pulleys and other rigging. Basically we made a human mule chain and towed it upright with rope where possible, then used a 3-1 pulley configuration and towed it straight up some 40 degree pitches trying to stay in the trees on the more solid snow. We tried a sled under the skid but it washed out to much and wasn't worth it. We basically manhandled the thing for 2.5 miles and 2000 vertical feet. I was worthless today! If it had been a 300, I would have gone in with a topend kit and tools and repaired it in the field.

 

[dooman92]

Wow, that sounds like an experience. Glad you got it out, and yeah makes a case for the 2 stroke.

 

[chumbilly1]

My thoughts exactly. I have a sweet 450sx but don't think it will ever see the snow. 300 will be my pick!

 

[M5-]

It sounds like you guys are better equipped than most. We have done a bunch of chopper rides over the years flying broken $hit out of tricky places and basically its always a grand. At that price it makes the cost of owning a spare motor look pretty good, just swap it out in the field and go again. Might be the answer for bikes then you could be rebuilding one while still riding.

M5