07 kx250f having issues

[07kx250fmn]

I bout this bike a week ago for a good price. But it's got some minor issues I "hope". The bike pops on decel and a little bit at idle also when you start it with choke it's revs to the moon sounds like it wants to blow until you take choke off .. I did find a rusty hot start not sure if it's stuck on or off.. Would this cause these symptoms ?

The bike runs great lots of power starts we'll

Another issue I'm having is the bike vibrates at high speed makes my hands numb after a short ride on a wet dirt road.

Everything on the bike is stock beside the fmf q4 pipe. The last owner said the valves where in spec when he brought the bike in last. would a bad bearing cause this vibration ? Bent rim ?

I'm new to 4 strokes any help would be great

[07kx250fmn]

!!!!

[suzuki son of a bitch]

Sounds like a jetting problem. make the pilot jet one step richer and try that. Fasst flex bars are good for dampening out vibration. Also use thick grips to absorb vibration

[07kx250fmn]

Would jetting really make the bike rev basically full throttle when choke is on ?.

[majikman808]

Yup my 450 did that when i changed the pipe. Your pilot jet controls bottom end and idle. I had to change my main also

[07kx250fmn]

Should I order a jet kit from fmf ? Or should I just up the main and go from there.

"Pilot"

[07kx250fmn]

I forgot to add that I can feel the vibration in my legs when I squeeze the bike.

Thanks guys

[majikman808]

Start with your pilot jet first

[majikman808]

Does it vibrate when you're revving the bike on neutral or only when moving at high speed?

[suzuki son of a bitch]

Dont buy a whole jet kit. Just buy a few extra jets and try them all. Its a lot cheaper that way

[07kx250fmn]

It does vibrate in neutral when I rev it. Will do. I forgot to look what the pilot was when I took it out for cleaning

Thanks

[majikman808]

Did the previous owner do any engine work? Maybe he missed something. Counterbalance possibly off

[Shawn250]

Check all the engine mountings bolts are tight.

 

Normally the idling will climb very high on choke if the motor or outside temp is warm enough to run without the choke.

 

You can first try just turning the fuel screw out 1/2 to 1 turn and see what it does.  

Edited April 16, 2014 by Shawn250

[elwoodd]

If you end up checking valve clearances see if your timing chain is stretched. When I first bought my kxf it popped on decel like crazy because my chain was stretched nearly half a tooth.

[Dragon67]

If the hot start is stuck open it will rev with the choke on.  Choke = more gas, hot start open = more air.  You should fix that first.  The vibration is troubling (to me, anyway) because I would suspect the crank or crank bearings.  If the crank isn't balanced, or if it is thrown out of balance during assembly (which can happen if you don't use a jig or some other support between the two halves) you get vibration.  

 

A lot of times, in my experience, popping on decel is due to a loose header or bad gasket between the head pipe and the head.  Same with a cherry red head pipe.  That means oxygen is getting into the head pipe and mixing with unspent fuel in a superheated environment.  It ignites and pops, or just burns in the head pipe and makes it look cool.  Very, very easy to fix with a new copper gasket and the proper assembly of the exhaust.  It doesn't cause vibration, though. 

[07kx250fmn]

Thanks for in the input guys. I will be trying everything as soon as this 10 inches of snow that dumped on us today is gone. I don't think it's the motor this bike is extremely power full and runs great when warm no issues. I guess I just convinced my self that it's fine hope your not right

[07kx250fmn]

I've worked with motors my whole life and it's my job pretty much to keep our equipment running. I've seen many motors blow cranks bearings pistons etc.. Then again I'm new to four stroke dirt bikes not my forte...

[Dragon67]

Thanks for in the input guys. I will be trying everything as soon as this 10 inches of snow that dumped on us today is gone. I don't think it's the motor this bike is extremely power full and runs great when warm no issues. I guess I just convinced my self that it's fine hope your not right

 

i hope I am not right, too   it has been known to happen  ? Even if it is the crank, a small vibration is probably fine.  I agree with checking the motor mount bolts as others suggested.  Would you let us know if torquing them helps?

[07kx250fmn]

For sure. Have to go out plowing tonight so it's going to put a damper on things. Thanks for the help. I'm sure I'll have a few more questions..

[07kx250fmn]

Figured out the vibration. Cracked motor mounts tearing it down to get them tig welded.