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Let me preface this post by stating that I am new to the forum and also a relatively new 230 owner. I purchased a 2004 CRF230F a few years back and since then have only ridden it a few times. When I got it it was in rough shape and I've had to replace several things including the exhaust system. I went with the Pro Circuit T4 full exhaust because it was affordable and was a major upgrade to the pop can the previous owner had on the bike. I rejetted the carb with a 120 main and a 45 pilot because that was what I had read others did with the same exhaust system but the bike still bogged at high rpm. I recently discovered that there was an adjuster screw missing that threads vertically upwards on the one side which I assume is a mixture adjustment screw. I guess my question here is, does anybody have any information or know where to find anything about how to set the position on this screw? I understand how a carburetor works but I have little experience when it comes to the fine tuning. The elevation of where I usually ride is around 800 ft.

Hi DedolaDom and welcome to the site.
One you have described as an adjuster screw sounds like the idle mixture screw.
It is item 7 on this parts view.
https://partsfinder.onlinemicrofiche.co ... TOR%20ASSY.
You will need to check whether it has actually fallen out or if the bike still has the original screw which almost sits flat with the body.
If the bike idles ok then I would think it must be still in there, but you need to check. If it is the original 2004 screw it can be adjusted still but you can easily get burnt fingers. A tight fitting plastic tubing over the splines can make it simpler. You normally seat the screw gently then back it out say 2 turns. This should allow the bike to start. Once the bike is warmed up adjusting the screw slightly either way till revs peak at idle. If you are less that a turn out idle jet is too big. If you are more than 3 turns out the idle jet is to small. Good chance the screw will fall out at 3 turns out.

The idle mixture would have little effect on bogging at high rpm.
Does it feel like it is cutting out or just going flat at high rpm?
I would suggest you check the air filter is clean and not over oiled, ensure you have fresh fuel and a fresh spark plug properly gapped.
These things can effect higher rpm. The carby may still need a main jet change either way if the other suggestions don't cure the problem.
What was the idle and main jet before you replaced them?

Do you know which needle is fitted to the carb and what position the clip is on?

Thank you for the response! I actually replaced the screw with a spare I had from an All Balls carb rebuild kit but I can't recall putting a spring in with it as that assembly shows so I will have to purchase a new assembly. I am currently going to school out of my home area so I don't have access to my bike to check my needle or clip but I will post an update when I next have access to it. I am not sure what the original jets were, it has been a while since I have rejetted it. It was cutting out after about 3/4 throttle which led me to believe I had jetted it incorrectly, it was at this point when I noticed the empty spot for the idle screw. Last time I had the bike out though was in November and I cleaned and oiled the air filter but it wasn't too nasty before that. Again, I appreciate the response, I will hopefully be able to get the red devil running flawlessly once I have a properly rebuilt carb and tune it with the knowledge you provided.

I use this fuel screw.
https://www.crfsonly.com/catalog/produc ... ts_id/1362

Put spring on screw first followed by washer then o ring.
These are ordered as optional parts looking at the site .

Make sure there is not a o ring still stuck in carb.

I'll be sure to grab that screw, are there any other aftermarket parts you would recommend for a 230?

Best thing to do is make sure maintenance is up to date.
Set your rear sag and that will give you an idea if the springs are suitable for your weight with riding gear.
Having the correct springs for your weight and riding style makes the bike more comfortable to ride.
Don't get caught up with replacing suspension bits first up.
Make sure sprocket bolts are tight and spokes are firm.

A different set of bars to make you comfortable when riding but only if required.
A good set grips can make it better when riding too.
If you go back a few posts Jim reckons these ODI rogue grips are magic.

These are the grips , they really cut down on fatigue


And yea , 1 thing at a time so you know what did what , good or bad