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Carb question 97 CR250

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I just bought a 97 CR250 a few weeks ago.  I rebuilt the top end this weekend so I know what I have and it gave me a chance to check out the engine.

 

 

It had a bog on the low end/idle side and was hard to start when I got it.

I started to take the carb apart to clean it when I had the top end apart but it looked relatively clean so I decided to wait and ordered a carb rebuild kit.

While waiting on the kit to arrive I was doing some heat cycles and playing with the carb idle/air screw.

I had it idling pretty good with just the idle knob, when I had to carb off I reset the air screw to factory specs (2 turns out) so when I started turning the air screw the bike was going up and down almost like I was touching the throttle but I wasn't.  Is this normal???  I was expecting the idle to increase or decrease but it just seemed to be erratic.

Should I just wait till the rebuild kit comes in?  

Thanks for any help!

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I'm not sure, the quick/cheap check is to start it up and let it idle, or have someone blip the throttle if it doesn't idle, and spray WD40 or contact cleaner around all mating surfaces, the intake boot, the carb where ever air could leak in, and check for an increase in idle. If it idles up when you spray the boot, for example, then that let's you know it's leaking air there. If you don't find any leaks by doing that, then the next bet is the left-side crank seal.

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Good to know! I have the exact same problem with my 1997 CR250, idle goes Zam, ZAM, zim, ZAM zim ZAM zim, ZAM ZAM ZAM ZAM, like its pulsing, air leak! didn't even think of that, makes sense.

I'm also running 2 turns out, but it won't idle, I'm like 10 turns out on the choke to get it to idle, its been like that 2yrs for me now, but I think its causing problems on the low speed fuel circuit as sometimes I bog down low too, but thats usually after having the throttle closed idleing then I try to open it with some drag on the rear (mud etc) and it just dies and is hard to start.

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Hey,

Did you figure this out yet ?

I just purchased the same year bike and it idles erratic also.

I wouldn't say I figured it out completely yet...but I did rebuild the carb on Sunday with all new parts and I found that on the air screw there's a o-ring, washer then the spring.  My old one didn't have the o-ring or the washer which was probably the reason it was really erratic when I tried turning the air screw and one of the reasons it was hard to start.

So it started right up and was idling good just by turning the idle knob (but my idle knob is turned pretty far out too).  I also didn't notice the slight bog it had sometimes off idle that it had prior to the rebuild.  I had to do something else that day so I didn't get to ride it yet.  I'll post you up after I do.

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Update.

I was still having issues with this carb although I feel the work I did on it made it better than it was....so I ordered a new choke/idle screw since thats the only thing in the carb that wasn't replaced.  While waiting for it to come in (on back order) I just said eff it and bought a Lectron carb.  

Wow what a difference it made!!  The bike starts right up and idles perfect out of the box!  I replaced the throttle and everything.  It seems very crisp throughout and way more responsive.  Highly recommend this carb so far.....

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Those carbs like to leak at the choke. There is an O-ring that goes bad there

I would say this is very accurate....I got the new choke knob today, but I already bought a new carb and put it on so I doubt I will go thru the extra work to test it when the new Lectron is working flawlessly right now.

So if anyone is having a similar issue I would START with replacing the choke knob first.  Would've saved me a lot of time and money.

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I would say this is very accurate....I got the new choke knob today, but I already bought a new carb and put it on so I doubt I will go thru the extra work to test it when the new Lectron is working flawlessly right now.

So if anyone is having a similar issue I would START with replacing the choke knob first.  Would've saved me a lot of time and money.

Yeah, I put some teflon tape on the threads of mine and it made it a little better. I just got sick of having to mess with the jetting constantly, so I picked up a Keihin PWK AS from a 2000 CR250. It gave it more power, and since I got it dialed in I haven't had to touch the jetting :thumbsup::ride:

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