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07 crf150r hang idle once in a while?

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My jetting is right on with recommendations for 700ft and 70degrees in summer. I actually enrichened pilot by one step thinking it was a lean condition. I have a 135m, NHNT needle 3rd from top, 42pilot. This bike acts strange whens its cold, when warmed it wont idle correctly, so when i bring idle up it wont increase rpm until i wack throttle, then it revs outa control. Once i fiddle around and get it running fine it runs good but when bike comes back to idle it still acts up sometimes but not always. It changes from time to time, its like it does what it wants. It requires a whack of throttle to start like it loves fuel but with i do plug look it is brown and sonetimes a little on the black side. Very tempermental bike. Am i just too picky or should i be replacing parts like slide plate, main jet holder, needle for worn parts? I brought float up .38 to 7.38 thinking it will help (didnt start it yet). I spray wd this summer thinking i had air leak in boots, nop. Anyone skilled with this bike please help? Dont get me wrong this bike runs healthy on the go, its a monster

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Float height isn't so much important with four strokes....

 

The trouble spots on  the FCR carb are the slide plate seal, the fuel screw oring, the hot start plunger and cavity, and the needle jet (emulsion tube), when it's worn.

 

Your carb is now 9 years old, so the moving parts are losing tolerance.

 

The hot start can cause all sorts of confusing issues, especially hanging idle, due to the plunger not sealing really well due to corrosion.

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Ok, ty. Plate seal alone is 90.00. I pushed on plate and it had recoil. I will try replacing main and tube and needle. I did notice someone tried to "free" float needle brass sleeve by using a flat head screw driver because it had nicks in it. I used a fine half round file to clean burrs on edge and cylinder. I filled chamber with water while needle was seated to see if it seals, it did. So, if float needle was hesitating it might help. But, i have a hunch that i should buy new main, main tube, needle and float needle for deductive reasoning maybe?

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Why would float height not be so important? Is it more so with 2t bikes? Why? Curious..

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If hot start is not depressed or touched in any way with these reoccurring intermittent problems, would its mechanical operation still come into play?

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Crfsonly.com sells the seal for $16

Hot start cavity acts like a bucket for water, which drips down the hot start cable, and it all corrodes in there.

Once corroded, it spreads like fungus and messes up everything.

No reason for a new main, but yes on a new pilot. You cannot clean the inside of a pilot jet without a sonic cleaner....

 

Two strokes have more vacuum pluses than four strokes with a very consistent vacuum, so their carb settings are touchy

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Wow! Great deal. Hot start cable looks good, cavity and plunger all look good. Should i try a spray when running to see if its air tight? I will sonic carb and jets at yam shop maybe as precaution. I was always under assumption since needle and main touch there would be wear, i guess its not important in my case. I looked at jet chart in my manual and im blown away that at 999ft the pilot remains same from freezing to 100degrees!!! Only main changes?? Screw stays at 2 1/4, theres hardly any room for movement, crazy.

Also i noticed that the last owner musta thought that brass insert for float needle comes out with a little prying? I had to clean up a couple burrs where he nicked insert with a half round fine file so needle slides without hesitation

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Header crush washer, slide plate seal, pilot jet passage above the jet gets partial passage clogged, hot start leaking, cracked hot start cable cap is cracked not allowing for enough pressue on the hot start plunger, bad fuel screw washer, allow fuel screw (must use brass), fuel screw adjustment technique, and a loose 'push' cable on the carb all can contribute to hanging idle.

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Idle is controlled in the pilot circuit. I know with my KX250, I went leaner on the pilot so I had to back the air screw in a half turn. Leaner pilot means less fuel, and therefore means more air. You went up on the pilot so you might need to adjust the air screw out some.

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Header crush washer, slide plate seal, pilot jet passage above the jet gets partial passage clogged, hot start leaking, cracked hot start cable cap is cracked not allowing for enough pressue on the hot start plunger, bad fuel screw washer, allow fuel screw (must use brass), fuel screw adjustment technique, and a loose 'push' cable on the carb all can contribute to hanging idle.

thanks, i will look at hot start cap again, looked good, no cracks in cable to leak water into cavity, header crush washer? Interesting, i will look on head for one. Yes my fuel screw is after market alum. Push cable? Like one of the two throttle cables? I will look again but when i crack throttle that spring on slide is powerful and pulls slide down nicely, however its a great idea to look at it closely in its operation, i will relube cables too. Your about the most knowledgeable on here with ideas, i get alot of basic hypothesis from most, im not a beginner on mechanics, just stumped. This bike is very touchy and high performance. My yam 450 is easier for dome reason, same carb set up too, fcr.

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These 'last generation' carbs are pretty good performance wise, but they do have internal parts that are designed to wear out and be replaced (slide seal, slide plate, needle jet, apump diaphragm) and they really start to get bad at about 250+ hours (slide bore gets worn out). You just have to get a new one at that point.

 

Add to that the balancing act of hot start condition / choke condition / wear items / changing air density / fuel screw adjustments/ vent hoses clogging or sucking in dirt / and just plain neglect, and you can see that the FCR's performance is made up of a somewhat difficult alignment of many systems.

 

Re-buidling the entire carb (not just pulling the jets and spraying cleaner) is the only solution to a 'problem' carb in some cases, but usually, it's either contaminates in the jets, corrosion (ethanol poisoning) of some or all components, worn out parts, or improper tuning.

 

 

 

I am far from the most knowledgable contributor here....I am just single, and in from of my computer a little to often, and have struggled to understand the FCR carb since 2002. 

I feel now I can figure out just about anything, eventually,  but still sometimes struggle with the FCR on my 450X....usually from continually corroding hot start components....

 

I turned to William and Eddie years ago, and they showed me that the FCR is not as cryptic as all that, but I think carbs are like IT Networks: nobody really knows everything about them, no matter what they claim !

 

Really great resources:

 

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

 

http://www.pbase.com/jdjetting1/keihin_fcr_manual_views&page=all

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Mine requires me to let the clutch out in gear to lower the rpms below the hung idle. Ive been dealing with this for 2 years and finally started throwing parts at it (all new jets, new mixture screw, new orings and a new intake boot so far). I have the slide plate seal, choke plunger and hot start plunger on its way for another rebuild next week so I'll keep everyone updated as to what does it for me. I have what the manual recommends for jetting but am curious to try what Pro Circuit recommends after I fix the hung idle.

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Thanks guys! I will inspect it. Its weird how you can adjust idle and not get response like most carbs immediately, then after a few turns it revs outa control when wick of throttle. Then you turn it down and start over. Weird. Ok thanks guys

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Thanks guys! I will inspect it. Its weird how you can adjust idle and not get response like most carbs immediately, then after a few turns it revs outa control when wick of throttle. Then you turn it down and start over. Weird. Ok thanks guys

 

Classic hanging idle.

 

It's an air leak, not a jetting issue.

 

Put in a new, correct, fuel screw oring too

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Yes, sorry i thought i mentioned it comes and goes. It happens alot when i adjust idle up and it does not idle up till i wick it then it idles wild. Yes i ordered stock fuel screw and washer. Needle for bowl, needle jet,emulsion,M jet, slide seal, just in case. I will lub and inspect idle screw, spring on throttle body and inspect cable operation as well.

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Yes, sorry i thought i mentioned it comes and goes. It happens alot when i adjust idle up and it does not idle up till i wick it then it idles wild. Yes i ordered stock fuel screw and washer. Needle for bowl, needle jet,emulsion,M jet, slide seal, just in case. I will lub and inspect idle screw, spring on throttle body and inspect cable operation as well.

...and service the hot start for any corrosion

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