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1996 YZ250 Problem

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NEED HELP

I have a 1996 yz250 2stroke dirt bike.

 

I bought the bike about a month ago, it has a new top end and fmf gold pipe on it. The guy told me the bike had to be rejected for the pipe. so i rejeted the bike to spec.... i have been having issues with 3/4 4/4 throttle range in id say 1st 2nd 3rd gear. Know i figured it needed a bigger jet so i went up a jet size. nothing . ran a little fatter but still had problems in that 3/4 4/4 throttle range. It tends to feel like a hesatation or some what like a rev limter. I figured the bike was starving for fuel. i changed the main jet about 5 times along with various clip postions and no change in 3/4 4/4 throttle range. So i decided to rule out the carb.(cleaned the carb at least 10 times) I also checked to make sure the power valve was in working condition and it is . I also repacked the exhaust and put in a new air filter. Compression is good and reeds are in good shape. I’ve also tried a couple spark plugs but no change in performance .Spark looked good last i checked.

 

Now I’m starting to feel it’s something electrical . Possibly a bad stator? CDI? or Ignition coil? Can something go wrong where it doesn’t let the bike rev past a certain rpm? (in my case the last rpms of each gear) I also checked the wire harness that runs to the case and cdi box, everything checks out and is in good condition.

 

I’m starting to think the stator is going bad or possibly a wire is cracked... i don’t know too much about that part of the bike, but could that be the cause of the rev limiter feeling I’m getting?

 

any suggestions are help :) thanks Craig G

Edited by craig12345

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I would raise clip to drop the needle to lowest position and see if it helps. Like arnego posted.....try to lean the topend and see if it helps. is that a PWX carb with the choke knob idle? Does it have surge at idle?

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NEED HELP

I have a 1996 yz250 2stroke dirt bike.

 

I bought the bike about a month ago, it has a new top end and fmf gold pipe on it. The guy told me the bike had to be rejected for the pipe. so i rejeted the bike to spec.... i have been having issues with 3/4 4/4 throttle range in id say 1st 2nd 3rd gear. Know i figured it needed a bigger jet so i went up a jet size. nothing . ran a little fatter but still had problems in that 3/4 4/4 throttle range. It tends to feel like a hesatation or some what like a rev limter. I figured the bike was starving for fuel. i changed the main jet about 5 times along with various clip postions and no change in 3/4 4/4 throttle range. So i decided to rule out the carb.(cleaned the carb at least 10 times) I also checked to make sure the power valve was in working condition and it is . I also repacked the exhaust and put in a new air filter. Compression is good and reeds are in good shape. I’ve also tried a couple spark plugs but no change in performance .Spark looked good last i checked.

 

Now I’m starting to feel it’s something electrical . Possibly a bad stator? CDI? or Ignition coil? Can something go wrong where it doesn’t let the bike rev past a certain rpm? (in my case the last rpms of each gear) I also checked the wire harness that runs to the case and cdi box, everything checks out and is in good condition.

 

I’m starting to think the stator is going bad or possibly a wire is cracked... i don’t know too much about that part of the bike, but could that be the cause of the rev limiter feeling I’m getting?

 

any suggestions are help :) thanks Craig G

Have you made sure that your clutch isn't slipping? I went through all of this diagnosing and then was told by BDubb over here that it was my clutch. Could you possibly upload us a video so we can hear what you mean exactly?

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Electrical components you check over the resistance OHM value.

Your manual should have those numbers.

 

Have you tried to go leaner or just went up with the main?

I leaned it out and had the same response . also I've adjusted the clip position 1-5. but I will check the electrical next. thanks for your input!

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Sounds just like that . but it goes away in 5th gear?

Don't replace the whole coil assembly and don't let the dealer talk you into it. Start by replacing just the plug boot. $4 part  at your local dealer. I bet your issues go away.

 

This is the part that you want.

http://www.rockymountainatvmc.com/p/43/-/171/954/-/35090/NGK-Universal-Spark-Plug-Cap-90-Degree-Elbow?term=spark%20plug%20cap

Edited by BDubb106

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Don't replace the whole coil assembly and don't let the dealer talk you into it. Start by replacing just the plug boot. $4 part  at your local dealer. I bet your issues go away.

 

This is the part that you want.

http://www.rockymountainatvmc.com/p/43/-/171/954/-/35090/NGK-Universal-Spark-Plug-Cap-90-Degree-Elbow?term=spark%20plug%20cap

thanks for your help . that's what ill do next

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Are you still having the same problem? I'm having a similar problem and I'm not sure what to look for.

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I see you checked the power valve. Our 96 YZ250 went *really* flat early this season. That turned out to be the power valve governor broken up.

 

Well worth trying a new plug cap as suggested. In my experience stator winding faults usually lead to hot starting problems or losing spark completely after a few minutes running, then coming back when cooled off. Having said that, I did have a Morini that wouldn't rev out due to a winding with low resistance but their system is ^really* weird. Check the winding resistance cold and hot and search for even the slightest looseness in connectors in the ignition system. Vibration can do strange things.

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I am also haven the same prob.. i still cant figure it out ..BDubb106 im going to try your idea out.

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