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Help please.. Hanging idle!!!

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Hello all

I'm hoping some of you can guide me in the right direction. I'm having a hanging idle problem on my sons crf150r and I cant seem to find the problem. I have removed carb twice and thoroughly cleaned it. replaced the pilot form a 42 to a new 45 and replaced the fuel screw with a new one. I have tested the fuel screw from 1-3.5 turns in 1/4 turn increments.  I can lower the idle enough to eliminate the hanging but the bike will stall if not blipping the throttle every few seconds. I have sprayed carb cleaner around the joints checking for leaks with no luck. I have also removed the throttle cables and test ran just to eliminate the possibility of the cables hanging up. Im thinking valve adjustment or the TPS but not really sure. Any help would be much appreciated as I'am at the end of my rope with this issue. Thanks in advance.     

 

Edited by brappder

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2008 and not sure on the hours. We got it used less then 4 months ago and it had no meter. When I have the idle down to eliminate the hanging it rides great. No bog and smooth power through the rpms.  

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Slightly bent needle?  It happens.

Most problems with the idle hanging high are cable related, though.  Just because the cables work smooth when you take them off doesn't mean that once they are routed and everything is back together they aren't getting kinked or squeezed.

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Just now, cjjeepercreeper said:

Slightly bent needle?  It happens.

Most problems with the idle hanging high are cable related, though.  Just because the cables work smooth when you take them off doesn't mean that once they are routed and everything is back together they aren't getting kinked or squeezed.

I'm thinking of just replacing the needle, main jet, carb seals  and see what happens. I have also read that if the pilot is to rich and you have to open the throttle screw to much to keep it running, that can cause the hanging. I have ran it with the cables disconnected with the same results. 

Edited by brappder

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Just now, S.O.A.N.Z said:

a worn slide can also cause your dilemma

How can I check this? When I had the carb out cleaning it, the slide seemed to snap down with no problem.

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The KLX450R has that problem from the factory. Not cable or slide or needle related because they are all new.

When letting off the throttle, it is like it has some excess fuel stored somewhere and idles high, but after a couple seconds the idle returns to normal. Is that what your symptom is?

Some say they fixed it by unplugging the TPS.  For me, once I got the pilot jet dialed in it went away. Did you try going smaller on the pilot?

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6 minutes ago, wielywilly-g said:

The KLX450R has that problem from the factory. Not cable or slide or needle related because they are all new.

When letting off the throttle, it is like it has some excess fuel stored somewhere and idles high, but after a couple seconds the idle returns to normal. Is that what your symptom is?

Some say they fixed it by unplugging the TPS.  For me, once I got the pilot jet dialed in it went away. Did you try going smaller on the pilot?

Yes, that is exactly what is happening. It had a 42 pilot and I replaced with a 45 thinking it was lean causing the hang. I might try and go back to the 42 and dial in the fuel screw. I think ill just order the flexible one so I can adjust while running. With the stock fuel screw I have to shut the bike off and turn the carb to access the screw. 

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1 hour ago, brappder said:

Yes, that is exactly what is happening. It had a 42 pilot and I replaced with a 45 thinking it was lean causing the hang. I might try and go back to the 42 and dial in the fuel screw. I think ill just order the flexible one so I can adjust while running. With the stock fuel screw I have to shut the bike off and turn the carb to access the screw. 

Why did you replace it?  If that is the stock jet and the bike is stock there was probably no reason to.  You are in Maryland, at or near sea level, the bike probably came jetted for those conditions.  Rejetting out here is the usual with the mountains, but it shouldn't need it on a stocker at sea level.

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Just now, cjjeepercreeper said:

Why did you replace it?  If that is the stock jet and the bike is stock there was probably no reason to.  You are in Maryland, at or near sea level, the bike probably came jetted for those conditions.  Rejetting out here is the usual with the mountains, but it shouldn't need it on a stocker at sea level.

I thought it was a lean pilot condition causing the hang and from what I researched most everybody running these go with the 45 pilot to eliminate the low end bog. I believe a 38 pilot is stock. Your right though I think i need to set it up as stock and go from there.  

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2008 and not sure on the hours. We got it used less then 4 months ago and it had no meter. When I have the idle down to eliminate the hanging it rides great. No bog and smooth power through the rpms.  

If you have the idle up too high you're are running on the needle diameter, not the pilot. I suspect it's a combination of incorrectly set idle and fuel screw.
Research how to properly set fuel screws. William 1 has a good post on here somewhere about it.

45 pilot is a known mod in the 150R world. The pilot circuit isn't as sensitive as the other circuits. 45 is a much closer starting point than 38.

That bike also has the old style FCR and benefits greatly from the O-ring mod.

Sent from my XT1650 using ThumperTalk mobile app

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So, after adjusting the valves and rebuilding the carb its running like a dream. One of the intake valves was less then .002 and I suspect this was causing it to not idle well and making me have the idle screw to far in which caused the hanging. I also installed the RnD Flex jet and I highly recommend it. Its defiantly worth every penny. Thank you all for the help! 

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