230 jetting for both summer and winter

2003 crf230. Stock filter, fmf pipe with most of packing gone.

Plug is looking pretty white and little decel popping.

I've been reading jetting on here and the difference in summer temps and winter. I'm in Deep South AL at sea level and now in summer it's 80-100+ degrees. It cranks very easy and have only had to choke it once after sitting 2-3 weeks.

No clue if it has stock jets or not but it seems lean. So what jets can I go to for hotttt summer AND cold close to freezing temps in winter. Thanks

Start with a 45 or 48 pilot and a 120 main.

....and needle 4 clips from the top. Fuel screw 1.5 to 1.75 turns out, and of course your intake baffle should be out too.

Ok thanks going to tear into it tomorrow. Anyone have a pic of the intake baffle, and what's required?Haven't pulled the seat yet, and not sure best way to remove and what exactly.

Fuel screw was turned out prob 4-5 turns so I'm guessing previous guy tried to get it rich as possible?

So that's the jetting most are running at sea level? With fmf pipe?thanks

Intake baffle is a plastic 'snorkel' of sorts that sits in the rectangular rubber opening at the top of the airbox.Purpose is to quiet intake sounds and it blocks air flow. It's the only air intake opening and it's directly under your seat. Friction holds it in and you just pull it out. If there's just a rubber framed hole then someone already pulled it out.

I like to also remove the 'backfire screen', a four layer wire mesh screen right under your air filter. Makes no sense to me why they need to make it 4 layers, but I'm guessing lawyers have something to do with it. Some day "don't take it out, it doesn't increase hp on the dyno," but in my experience, a dyno doesn't measure throttle response, and without it, I feel the difference!

Do this test: blow as hard as u can thru the screen with your hand on the other side.You can barely feel the air with your hand. If that's not restrictive, I don't know what it is! If taking out the screen will keep u up at night, only remove 3 of the four layers (start from carb side for a cleaner look), it has to help!

Ok thanks fellas. So I can use the stock needle just put it on the 4th notch. Then only jets I need to change are the pilot and main jet?

that should be the case yeah. i find that 120 is a hair rich so i use a 118. im in canada tho so in winter i might have to bump all the way up to a 125-130 lol

FishFreq.. is very attractive what you have recommended about the " backfire screen" removal

Have you done this? Have you raised all the layers?

Surely we will have an improved air flow.

Obviously there is a risk in this mod, even if I believe both remote, a possibility of flame in the air box with consequences potentially dangerous. Do you know if it is happened to a crf230 without the backfire to be burned?

FishFreq.. is very attractive what you have recommended about the " backfire screen" removal

Have you done this? Have you raised all the layers?

Surely we will have an improved air flow.

Obviously there is a risk in this mod, even if I believe both remote, a possibility of flame in the air box with consequences potentially dangerous. Do you know if it is happened to a crf230 without the backfire to be burned?


Very little to be gained with respect to an engine requiring maybe 40 CFM of air at best.

Surely Vortec CPI.. I agree, there will be little improvement.

However every small mod added to the other mod will make a good final work. Especially on modded engines with greater air need.

I always remove 2 of the three screens. (Center and carb side)

I leave the one that's next to the filter.

I will do this work too..'

ll wait a chance to do other maintenance.

I think it is necessary to disassemble the air box... right?

Very little to be gained with respect to an engine requiring maybe 40 CFM of air at best.


Not having a dyno, I can't go by anything else but the 'seat of my pants' feel VortecCPI. But I'd swear I can feel it. I can measure it by the width of my smile when I crack the throttle! 


Yes Crossplayer I've removed the backfire screen from every thumper I've ever had, and so far, no fire alarms pulled. I think if my filter caught on fire, the airstream would pull the flame right out. Don't think a motor can backfire when it's not running so I can't think of any other problems. 


It may be 'only 40 cfms' air flow, but with less restrictions, that 40 cfms can ramp up and ramp down faster without obstructions. Some of my bikes have had a coarse single layer of wire as a backfire screen, and it helped on even those, but our crf's have a crazy screen that basically has not one, no not 2, or 3, but 4 LAYERS OF MESH, two of them very fine, with no real good reason for them, other than lawyers. I've never heard Honda, Yamaha, etc., explain why they sell certain 'entry level' bikes with all sorts of baffles, throttle restrictions, and the like other than to stay out of court. It COSTS them more money to sell us motorcycles that are CORKED UP, so it must be worth it. If you choose to remove those items after purchase, then they are legally absolved from any suit. 


What's the logic? Anything that I've missed, please point it out.


I look at it this way: if my home's sliding screen door had 4 layers like my crf, that 3 mph breeze cooling my house in the evening is just gonna stop! I mean, why else would passive intake products like the Boyesen Power X-Wing, Loudmouth Air Filter systems, or the 2012 Product of the Year, the Moto Tassinari Air4ORCE tuneable intake system not only exist, but find their way, unsponsored, onto the bikes of so many serious racers? Because they can FEEL the difference! BTW those items are not available for our crf's. 


When I took my stock uncorked crf150f and removed the backfire screen as well as ground smooth the huge ugly weld at the head end of the inside of the exhaust pipe, it was amazing! I'm sure in reality it was less than a HP, maybe only .25 hp, but throttle response was definitely up. It's never had any stumbling or hesitation problems so I wouldn't know if it cured that, but it sure made tuning and jetting easier. ....and my smile bigger! 


Every tuning situation is different, every rider is different. Friends that have ridden my bike, some of them are so timid, they wouldn't have felt it if I let the air out of the tires! Since we can't see the air and how it's swirling thru our engines, we can't tell if a modification is doing good or bad. So mods like this take a little luck to have work. 


To take it out, you have to first remove some white glue Honda put around the edge of the wire, then I used a torch to melt some soldier-like metal at the corners of the attachment. Then I took a dremel with a small grinder bit and smoothed out the soldier burrs. Oh, and this was after I removed the entire airbox, and unbolted the metal filter plate off the plastic airbox or there would be some serious melting going on. Then I soap washed and dried all the parts...


Please note that if you take out your backfire screen out you do it at your own risk. If your bike catches on fire because you did this I accept no responsibility, expressed or implied, by modifications you performed and other factors that could negatively affect the outcome! My lawyer insisted that I include that line! 

FishFreq .. have you raised all the layers? Did not you leave at least one?

Where are y'all ordering the 120 jet. I've found the 45 but rocky mountain and Motosport only go up to a 112

Your Honda dealer has that 120 main, and a'la carte, it's about $6.

FishFreq .. have you raised all the layers? Did not you leave at least one?

Crossplayer, I removed all 4 backfire screen layers from both my crf150f and 230f, I've done this with other thumpers for years with no trouble. How is it going to catch on fire? Neither bike has backfired thru the carb. If timing chain jumps, bike won't run. If the bike is running, any flame will be vacuumed out, IMHO....?

....and yes, completely disassemble the airbox, even the metal filter plate from the plastic shell. You don't want wire frag in intake. If u use torch to melt glue/solder plastic would melt.

Ok .. FishFreq will be my next mod.

Now this becomes interesting to add to my exhaust mod and my bored carb.

Now my best carb setting is 122 main jet. (45pilot + pin in the fourth notch from above in the 05 needle).

Ok .. FishFreq will be my next mod.

Now this becomes interesting to add to my exhaust mod and my bored carb.

Now my best carb setting is 122 main jet. (45pilot + pin in the fourth notch from above in the 05 needle).

You may just need to adjust fuel screw a bit after removal but let me know what you think of all that wire mesh and screen in there, it's nuts!

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      Jetting the 230F
      By: Phil Vieira
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      Where the red dot is where the needle lies. Grab needle nose pliers and carefully pull up the needle out of its slot. This is what the needle looks like once it is out.

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      From left to right: Main jet, Pilot Jet, Fuel screw. Now in the main jet’s hole, if you look closely, you see a bronze piece in the middle of that hole. We are going to take this off. Since I did not do this part (I only changed my pilot jet when I took these pictures) there are no pictures taken for this section but this is really simple to do if you’ve been a good student and know where things go. You should know anyways, you have to put the bike back together!
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      If you look directly under the carb, the round hole is aligned with the pilot jet. Take the float bowl, and put it back on.
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      The top clip position is #1, the lowest one, closest to the bottom, is #5. (The picture says six but it is five in this case) For reference #1 is the leanest position, while 5 is the richest. I put the clip in the 4th position. Read at the bottom of the page and you can know what conditions I ride in, and you can adjust them to your preference.
      Put the clip in the new needle, slip it in. Take the vise grips off your grips and start guiding the plunger holder down to the bottom. Remember not to let that assembly come apart because it is a pain in the ass to get it back together! Once you get it to the bottom, put the two screws on, and then put the cover on.
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      As you can see, you can slip your fingers in and pull it out. Do that. This lets more air in to the air box. Don’t worry about water getting in. There is a lip that is about 1/8” high that doesn’t let water in. When you wash, don’t spray a lot under the seat, but don’t worry about it too much.
      The next thing you must do is remove the exhaust baffle. The screw is a torx type, or you can carefully use an allen wrench and take care not to strip it:

      The screw is at the 5 o’clock position and all you do is unscrew it, reach in, and yank it out. This setup still passes the dB test. The bike runs 92 dB per AMA standards, which is acceptable. Just carry this baffle in your gear bag if the ranger is a jerk off. I’ve never had a problem, but don’t take chances.
      That’s it! Start putting your tank on, seat, and covers. After you put the seat on, pull up on the front, and the middle of the seat to make sure the hooks set in place.
      Turn on the bike, and take a can of WD-40. Spray the WD-40 around the boot where it meets the carburetor. If the RPM rises, you know you have a leak, and the leak must be stopped. You must do this to make sure there are no leaks!
      Here is my configuration:
      04’ 230F
      Uni Air filter
      132 Main Jet
      45 Pilot Jet
      Power up needle, 4th clip position
      Fuel screw 1.75 turns out
      Riding elevation: 2000ft - Sea level
      Temperature – Around 60-90 degrees
      Spark Plug Tips
      When you jet your carb, a spark plug is a best friend. Make sure your spark plug is gapped correctly, (.035) but that’s not all that matters. You want to make sure the electrode is over the center, and you want the electrode to be parallel, not like a wave of a sea. Put in the plug, and run the bike for 15 mins, ride it around too then turn it off. Then take off the spark plug after letting the bike cool. The ceramic insulator should be tan, like a paper bag. If it is black, it is running rich, if it is white, it is running lean. The fuel screw should be turned out if it is running lean, and turned in if it is running rich. Go ¼ turns at a time until your plug is a nice tan color.
      Making sure your bike is jetted correctly
      While you are running the bike for those 15 mins to check the plug color, you want to make sure it’s jetted correctly now. Here is what the jets/needle/screw control:
      0- 3/8 throttle – Pilot jet
      ¼ to ¾ throttle – Needle
      5/8 – full throttle – Main jet
      0-Full – Fuel screw
      Pin the gas, does it bog much? Just put around, is it responsive? When you’re coming down a hill, the rpm’s are high and you have no hand on the throttle, does it pop? If it pops, it is lean and the pilot jet should be bigger. If it’s responsive your needle is set perfectly. You shouldn’t have to go any leaner than the 3rd position, but I put mine in the 4th position to get the most response. Your bike shouldn’t bog much when you have it pinned. If it does it is too rich of a main jet.
      Determining the plug color, you will have to mess with the fuel screw.
      That’s it, have fun jetting, and any questions, post on the forum, but remember to do a search first.
      Also, if your bike requires different jets due to alititude, humidity, or temperature, please post the following so we can better assist you:
      Average temperature
      Altitude (If you do not know this, there is a link in the Jetting forum that you can look up your alititude)
      Average Humidity
      What jets you are currently running
      What the problem is (If there is one)
      Just do that and we'll help you out the best we can.
      EDIT: The girl using this login name is my girlfriend. You can reach me on my new login name at 250Thumpher
      Then again, you're more than welcome to say hi to her!
      -Phill Vieira
    • By jason230
      Well I figured this would be a cool thread to have seeing as how quite a few of us have gotten pretty far into upgrading our 150/230s. This will be helpfull for those looking into getting things for their bike so they can see what everything looks like.
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