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Engine racing / erratic idle problem

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I'm completely new to this sport.  I bought a 2005 YZ250F that had been sitting for a couple of years.  I rebuilt the carb and checked the valves, it can be hard to start when cold but does eventually fire up. I let it warm up on the choke and then set the idle with the choke off.

 

On my first visit to the track, I took off and rode through 4-5 corners (first time ever riding, I was going really, really, really slow!)  Pulling into the next corner it felt like the throttle was stuck open as the bike kept accelerating.  I dumped it/bailed off in the corner and it was still racing until I hit the kill button.  I wheeled it back into the pits and adjusted the throttle back down to a reasonable place.  I took off again and this time it died and wouldn't restart until I turned the idle adjustment back up, or gave it gas on the throttle.  Then while sitting (and not even touching the throttle) it started to race again. 

 

It basically seemed like there was a fast idle kicking in and then it would kick down to a regular idle.  If I adjusted the idle knob while it was on fast idle, it would die when it kicked down, but if I adjusted it while it was kicked down it would then race on to the fast idle.  It seemed to be totally random.  It made it really hard for me to ride because I kept being nervous going into a corner that it was going to try and take off on me.....

 

Any thoughts?

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Damn!  I was really careful about trying to put this back in the right direction.... but you may be right.  I'm a rookie and it's possible that during the 5-6 times I had the carb off and apart that it got flipped.  I'll check it.  Thank you.

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So I finally had a chance to spend some time in the garage.  The valve plate was installed correctly (with the hole at the bottom.)  The seal looked good.

 

I read this is a "wear" part and should be replaced from time to time so I decided I would order a new one.  Holy crap!  They are $120?!?!?! 

 

How do I confirm this is my issue before dropping that kind of money for a new plate and then still having the same issue?

 

The part that I looked up to replace is " 5JG-14546-01-00" and that doesn't even include the rubber seal.  Is that right?

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The hot start is all new but the o ring does seem a little odd. What order does it the cable/piston/oring get installed in? Does the o ring sit on top of the piston or below it? Which direction does the oring go in?

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The hot start is all new but the o ring does seem a little odd. What order does it the cable/piston/oring get installed in? Does the o ring sit on top of the piston or below it? Which direction does the oring go in?

 

A 2005 YZ250f hot start shouldn't  have the oring type plunger.....

 

hotstart001.jpg

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That's the plunger and nut that I've got but mine is cable operated and a little lever on the clutch side bars. I see I'm missing a spring and it makes sense why the oring shouldn't be there. I had it on top of the plunger but it didn't seem right. I don't think it effected anything though.

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Looking at ronayers.com fiche, it shows an o-ring for 2005.  Part #42 in this diagram but it's completely unclear where it goes....

 

qgh3Jed.png

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Looking at ronayers.com fiche, it shows an o-ring for 2005.  Part #42 in this diagram but it's completely unclear where it goes....

 

qgh3Jed.png

 

If you have that kind of plunger, it does have a ring seal, but it's not an o-ring. I've never seen that kind on a FCR CR-MX carb

 

http://www.ebay.ca/itm/kawasaki-carb-carburetor-hot-start-plunger-kx250f-most-/401043526777?hash=item5d600e9479

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If you have that kind of plunger, it does have a ring seal, but it's not an o-ring. I've never seen that kind on a FCR CR-MX carb

 

http://www.ebay.ca/itm/kawasaki-carb-carburetor-hot-start-plunger-kx250f-most-/401043526777?hash=item5d600e9479

 

I wonder if the seal is supposed to fit over the plunger.  There's a nice little relief in the middle of the plunger that it may just slide on to?

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Alright, replaced the hot start mechanism (with a spring this time.)  Replaced the throttle slide seal.  Made sure everything was buttoned up..... Bike started right away, idled fine once it was off choke but about 6-7 minutes later it started racing again.  Turned down the throttle, rode it around the yard a little bit and it died (too low of idle.)  I just can't find the sweet spot..... either it is racing or it will die.

 

What's next?!

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Alright, replaced the hot start mechanism (with a spring this time.)  Replaced the throttle slide seal.  Made sure everything was buttoned up..... Bike started right away, idled fine once it was off choke but about 6-7 minutes later it started racing again.  Turned down the throttle, rode it around the yard a little bit and it died (too low of idle.)  I just can't find the sweet spot..... either it is racing or it will die.

 

What's next?!

 

Lower the idle as low as it will go, with the fuel screw set at 1 turn out

Turn the fuel screw out to raise the idle

If it's too high, lower it with the idle screw

 

If you can't seem to do this, you still have an air leak.

 

Spray some brake cleaner all around the carb while running and listen....including the bottom of the carb

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Problem found.  Crack in the case.  &%$#@! previous owner smothered it with JB weld.  :lame: Rebuild thread coming soon.

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