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  #1  
Old 06-02-2016, 12:34 PM
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Default 1986 CR250 Idle Surge

     

Hello all,

I recently picked up a 1986 CR250. Having one hell of a time figuring out my surging idle issue. Here is what i have tried so far :

And here is a video of the idle while messing with the idle screw. : ( will post link after my 5 posts) My youtube name is "Supersickns" if anyone wants to watch it.
  • Set the idle screw 1.5 turns out. The bike will only idle near as it should if the screw is literally 1/8th a turn out. No more no less. At 1:30 in the video is what it idles like with the screw set in the 1.5 turns out position.
  • Pulled the PJ carb off and confirmed it has the correct #175 main jet, #60 pilot jet. The float valve is good. I may need to adjust the float level a bit.
  • Ive taken the reeds off and inspected them and they are all good. Even tossed another set i have in to see if it made a difference and it hasnt.
  • Put a BR9EG plug in the bike (Previous owner has the wrong plug (BR6ES) installed. I know a BR8EG/ES is the factory plug but a BR9 is a better option than the BR6.
  • My next step is going to be 1. Float level, and 2. Trying a PWK carb that i have as well. That carb has a 185 main 55 pilot jet setup. Just to see what if any difference it makes.
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Old 06-02-2016, 01:54 PM
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The idle mixture screw setting of 1/8 turn indicates to me that you are lean for some reason. Maybe a small air leak or restricted fuel flow.
Now keep in mind that some of the mid-80's cr's of 125 and 250 had a serge in them when all was spot on, so you may not cure it 100%.
What does the spark plug tip color look like?
The reason I ask is that is it possible for you to have an air leak and also have a float level that is set too high and it will give you a problem sorting it out.

Paw Paw
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Old 06-02-2016, 02:33 PM
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Quote:
Originally Posted by PawPaw View Post
The idle mixture screw setting of 1/8 turn indicates to me that you are lean for some reason. Maybe a small air leak or restricted fuel flow.
Now keep in mind that some of the mid-80's cr's of 125 and 250 had a serge in them when all was spot on, so you may not cure it 100%.
What does the spark plug tip color look like?
The reason I ask is that is it possible for you to have an air leak and also have a float level that is set too high and it will give you a problem sorting it out.

Paw Paw
I will check those things out and reply back. Once i reach my 5 post limit i can share the video link.[COLOR="Red"]
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Old 06-04-2016, 03:03 AM
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Do a pressure test, (search the forum for how to)
You might have a leaking gasket somewhere.
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