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CRF230F/L Struggles with idle in 2003 230f

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I’ve been fighting this hanging rpm/erratic idle issue since day one. It’s a 2003 and had been sitting out for a while and the thing rings were bad. Bought it for $500. I replaced the top end and that’s it. Bike ran great but sometimes would idle high then drop after 15-20 seconds. The bike was already uncorked when I bought it and the jetting was stock. I pulled the carb and did a rebuilt kit on it. Changed to a 120 main and 45 pilot. Needle on 4th groove. My elevation is around sea level to about 200’. I even replaced the dry rotted air cutoff valve diaphragm. The bike still ran great but the idle issue was still present. So I took the carb back off and took everything apart again. What I noticed is the when the needle clip is seated into the top of the throttle valve and the needle is perfectly vertical with the valve, it does perfectly line up with that notch in the valve. The seat in the throttle valve appears to be worn and not perfectly flat. Is this by design? I’m wondering if this isn’t the issue the whole time. Today what I noticed is that when I just barely twist the throttle more and more the rpms increase as supposed to be don’t drop back when I let go. The throttle snaps back and is working properly though. The. If I blip it real quick rpms drop back down but sometimes drop below normal levels. 

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I’ve been fighting this hanging rpm/erratic idle issue since day one. It’s a 2003 and had been sitting out for a while and the thing rings were bad. Bought it for $500. I replaced the top end and that’s it. Bike ran great but sometimes would idle high then drop after 15-20 seconds. The bike was already uncorked when I bought it and the jetting was stock. I pulled the carb and did a rebuilt kit on it. Changed to a 120 main and 45 pilot. Needle on 4th groove. My elevation is around sea level to about 200’. I even replaced the dry rotted air cutoff valve diaphragm. The bike still ran great but the idle issue was still present. So I took the carb back off and took everything apart again. What I noticed is the when the needle clip is seated into the top of the throttle valve and the needle is perfectly vertical with the valve, it does perfectly line up with that notch in the valve. The seat in the throttle valve appears to be worn and not perfectly flat. Is this by design? I’m wondering if this isn’t the issue the whole time. Today what I noticed is that when I just barely twist the throttle more and more the rpms increase as supposed to be don’t drop back when I let go. The throttle snaps back and is working properly though. The. If I blip it real quick rpms drop back down but sometimes drop below normal levels. 


No mention of properly checking/setting the float level or your method of adjusting the idle mixture screw.

If both not correct it will never be as good as it should be..,
Last but not least:
Make sure that there is free play in the twist grip (cables not to tight)

Or better yet, toss the return cable and do not use it. (But you will still need some free play in the renaming pull cable.

Finally:
Lube the throttle cable with cable lube and a cable lube tool.
Disassemble throttle assembly, clean all (and handle bar end) with brake cleaner and compressed air.
Lube all sliding surfaces with silicon spray, re-assemble.
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What #adnoguy said. If still hanging/erratic is the throttle valve worn? On my xr600s the same conditions occur with badly worn throttle valve. If valve is ok and showing these systems I polish the valve in a lathe , particularly the bottom leading edge. Works well with xr600s where this is a common issues even with correct jetting and float levels

 

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Float height is set properly. That’s the first thing I checked and adjusted. Fuel screw is one and a half turns out from fully seated.  The throttle valve doesn’t look worn  but I can’t help to think that it is not something with that part of the assembly. 

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There’s plenty of free play in the twist grip. Throttle cables are new motion pro cables that I lubed before I installed. If I remove throttle cables all together and turn the throttle linkage it snaps back properly but rpms still hang...sometimes. 

 

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Ok all sounds great so far, but one more question:
How did you come up with the 1.5 turns out setting on the idle mixture screw?

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Warmed the bike up for about 10 minutes and turned the fuel screw in until it died. Then backed it out until it was running at the highest rpm. Then turned the bike and turned it clockwise while counting how many turns out it was which was 1 1/2.

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Warmed the bike up for about 10 minutes and turned the fuel screw in until it died. Then backed it out until it was running at the highest rpm. Then turned the bike and turned it clockwise while counting how many turns out it was which was 1 1/2.


Sounds all good then. No more ideas that I can think of without being there myself in person.

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??‍♂️ I’ve exhausted everything I can think of. I’m thinking mg600 might be right about the valve being worn. I say it doesn’t look bad but I have nothing to reference it to. I don’t have access to a lathe nor do I know how it should be shaped. I guess I will have to buy a new one. Looks like the cheapest I can find is around $45. That’s not bad if that’s the issue. Only thing is that I don’t know if that will fix it or not.

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Very fine sandpaper worked for me .   Just a light polish ,    After a good dip in carb cleaning solution  ......

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Just haven’t seen it mentioned but Have you checked for air leaks Between manifold head carb.

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I did check for air leaks between the carb and the intake side of the cylinder. Everything looks good. I actually replaced the intake boot when I first got the bike because the old boot was cracked. I replaced the boot the gasket and the o-ring.

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I recently had some hanging idle problems with my Oko carb after changing out the pilot jet at 2 beer thirty in the morning with my cell phone flashlight app. 

When I slide the carb in the intake boot it was slightly twisted ccw.  The carb casting tab did not slide into the notch on the intake boot.  That threw off the float level in the fuel bowl.  Once I reinstalled the carb correctly, the hanging idle went away.  

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☝️ I know what u are sayin. That’s an easy thing to overlook. But unfortunately that is not the case. However I was wondering, the throttle valve shaft, how much play side to side is that supposed to have? If any at all. Could the spring be worn out? I can’t help but think this is the only thing left that it could be but if not I’m clueless.

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Problem solved! Finally got it to run properly. What a relief lol. The problem was the emulsion tube or needle jet I guess. It was worn ever so slightly. So small that I thought I had properly check it  and deemed it still within specs. Turns out without a magnifying glass I couldn’t really see how much. I also wasn’t sure that it would be as easy as it was to remove and replace it. This whole time I was thinking that since it was pressed in it couldn’t or shouldn’t come out. Turns out I was wrong. Thx for the help fellas.

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