2002 Yamaha yz250f starting problem

My 2002 Yamaha yz250f will start the first or second kick when cold, but once I run it on the trails for an hour and then shut it off for a break, It will not start for some reason. Tell me if my technique to start I is wrong, I pull in the decompression lever kick it down to the bottom let out the lever, bring it back up then kick it. That works perfectly fine when it is cold. So I don't know what the problem on it is or if I have to take it apart and fix something. I am really not sure why it is not starting when it is hot. Since it is an 2002 I am going to install the auto decompression hot cam. To make it easier to start over all so I don't not have to use the decompression lever. Not sure if that will help. Need to know soon I am going to pipe stone some time soon. Thank you

Not sure about your starting description.  When I had manual decomp on mine I would kick slowly until it stopped on the compression stroke.   Pull the lever and move the kick starter a couple inches.  Let off the lever and kick hard.   

When the engine is hot it starts easier if you pull the hot start.

I went to auto decomp Hot Cams, it was worth it.  The only advantage I could see to having manual is that if you can kick it over without using decomp something is wrong.  

Being too rich on the fuel screw can make hot starts a pain. Be sure it is adjusted for a perfect hot idle.

Hey thank you I will have to get back to you on the fuel mixture. Hey flyandride thank you very much I will have to try your method of doing it. You method sounded a lot better than mine I wasn't even finding the compression stroke on it. Also how much did it cost for the auto decompression cam for you. Did you just get one off of one of the newer bikes or get one from hot cams. Thank you :ride:

I am able to kick it over with out using the compression stroke what now?

So is that making it hard for me to start it after it has been running? Am I screwed? What do I have to do?

If you can start it cold and not hot, it is not the cams. Adjust the fuel screw with the engine hot for a perfect idle.

So is the whole being able to kick it over with out the decompression lever a bad thing?

Your valve clearance might be tight and is allowing the compression to leak out, which allows you to kick it over without using the decompression lever. Or you might just be really, really strong!!! Typically, it should be almost impossible to kick over without using the decompression lever, so something is probably wrong.

This might be a stupid question, but what could have made my valves to tight allowing it to leak. I have not touched them and when I got the bike I was not able to kick it over without the decompression lever?

Edited by ctbboss


The valves wear and move up in the head. That brings them closer to the cams and if it uses up all the clearance between the cam and valve, the valve can remain open. That can be accelerated by allowing dirt in the intake.

So what could that lead up to? Also how much would it be to get that fixed?

The first step would just be to check your valve clearances which you should be doing occasionally anyway. It only takes an hour or so. That will tell you if they are even a problem or not.

Hey thank you I will have to look at that.

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