I just spent the weekend trying to lean out my KFX400. This bike has run flawlessly for me until now. Last weekend I ran it with absolutely no sign of a problem. I brought it home and washed it thuroughly. This weekend I took it out to Stoddard Wells OHV in the Mojave. Its about 2800 ft. I had a hard time starting the bike right away but got it running after a couple minutes. Then I hopped on and started checking out the area. Within 1 minute I had a serious loss of power some sputtering and what sounded like my rev limmiter kicking in real early. I limped back to camp and pulled the plug. It was black as could be. I rejetted down 5 sizes and jumped back on with exactly the same result...... To make a long story short I continued this process until I had basicaly completely rebuilt the carb with no positive response. I went through 4 plugs before I just gave up. Now I need help. I cant figure for the life of me why my bike is acting like it is. Keep in mind this is a fairly new quad with maybe 40 hours on it and previously it ran without any problems. In all reality it should have run just fine the way it was set up, I shouldn't have had to mess with the carb at all. What else could it be?

P.S. The bike starts and idles fine. It then sputters badly when asking for power, when (or if) I get past the sputtering it will rev and run in the higher gears but its noticeably week. In nuetral the motor idles and revs but it sounds like you are fethering the throttle even when you are not. Its almost like the rev limmiter is kicking in 3 or 4k early.

 

Are you thinking what I'm thinking? Hmmmmmm, sounds like you got some water where it should not have. Did you change the plug? Sounds like the secondary is breaking down? Thats why the plug is black, it's not hitting all the time when it should. Did you check the plug wire for water in the boots? Did you check for water in the tank? Water got somewhere? It's a good idea to spray everything with WD40.
Check all of this stuff and see what you come up with.

 

check your fuel cap breather it could be blocked causing a vaccum in your tank
next time it happens loosen your gas cap if it goes away thats your problem
it is just a suggestion and looking at your avatar pic it is a good possibility it could be blocked

 

to many variables put your normal jets in and fire it up at home and make sure it runs ok when i lived in socal i used to ride in victorville thats about 4000 feet and i had no problems there or in the valley you shouldn't have to rejett untill you hit 6000 feet or so also the higher the octane fuel you run the leaner your bike will run so a tank of race gas wouldn't hurt for high alt. 2 strokes are much more finickie to altitude changes uasally four strokes are ok

 

The plug wire on the plug side was clean. I didn't pull the other side. As for changing the plug, it was replaced with a new one 4 times. Thats $20 worth of plugs waisted, or fouled. The gas tank breather is clean and breathing like it should although that was something I didn't think of. Just checked it now [img]i/expressions/face-icon-small-smile.gif[/img]

 

The gas tank breather being plugged would cause a lean, not a rich condition... IMO, it is either electrical, the fuel system, or an air restriction... since you've been working on the carb, are you sure that the choke is not sticking, or that some gunk is not sticking the bowl float ??? is the air filter clean, & not over oiled ??? ( this is especially important with altitude changes )... on the Prairies, there is a rubber flap, under the front plastic, that is supposed to deflect some of the water spray from the snorkle & electrics, up by the handlebar... this can loosen, & cover the snorkle inlet, causing the quad to run rich... just a few more things to check...

 

like he says check your choke

 

When I removed the choke it was all screwed up. There was gunk and chunks of stuff aswell as the spring was all twisted up. Im not sure why it was in such bad shape but fixing this problem has had no positive effect on the way the bike runs. I replaced the spring and cleaned up the choke circuit. I have observed that the choke is working properly by removing the airfilter hose while running the bike with choke on and off.

Its entirely possible that I over oiled my filter since I didn't know that was possible I wouldn't have known to avoid it. I oiled the filter up just before running it. The K&N oil aplicator is a drip nossle and it requires that you basicaly dump the oil on the filter. Problem with this theory is that the bike ran the same with the filter removed completely.

 

If the fuel enrichener (choke) had that much crud in it, it's likely that the internals of the rest of the carb is no better. Also, use a rag to sponge up as much of the oil as you can get out of the filter. The oil is meant to coat the walls of the pores in the air filter, not fill the pores up.

 

Speaking of that, is there a better way to oil the filter? The pore spot on the K&N doesn't let you just do a little. I thought about using a regular spray applicator instead but I didn't have any laying around the house.


As for the rest of my problems I will find out soon. I am going to drop it off at the local dealer spend hundreds and more than likely not be completely satisfied with the outcome. I may bight the bullet and just have them replace the carb the cdi and the cams at least that way I know I will get it back better than it was before I had this problem.