KX250 Carb Clean & Jetting Check
Anytime I purchase a used motorcycle (like the KX250 I just bought), I typically will take apart the carburetor(s) to take a peek inside. Whether the bike is running fine or not, I know how many people feel the need to mess with carbs, and most of the time they are not jetted properly. This is especially true and important with 2 strokes! Afterall, running them too lean will eventually result in a blown up motor.
Now, the reason I decided to take this carburetor apart is that it is running rich. I hear KX250’s are a bit rich right from the factory, and this usually holds true for all 2 strokes. Running them a bit rich is much safer than lean. Another reason is that VForce3 reeds were included in the sale so I have to pull the carb off anyway to install them.
Running Rich
- Right after a cold start, you can turn off choke and engine will continue to run without bogging. Usually 2 strokes will bog a bit until warm.
- Previous owner said it fouls the plug every 3 tanks or so.
- Spooge in the silencer.
- Plug chop shows rich (plug is very dark brown to black).
Modifications To This KX250
- Pro Circuit platinum pipe & silencer.
- I will install VForce3 reeds before altering jetting.
Stock Jetting
2001 KX250 stock jetting straight from the service manual.
Carburetor: Keihin PWK38S
Main jet: 160
Power jet: 48
Throttle valve cutaway: 8
Jet needle: NAFF
Jet needle clip position: 2nd groove from top
Pilot jet: 52
Air screw: 1.5 turns out
Float Height: 6.5±1mm
How-To Video
The video above walks you through how to clean and verify jetting for this carburetor. The jetting was found to be stock, which is great news since I now know reliability was not compromised.
Future jetting
It’s still cold here and a few weeks away from taking this bike out after installing the new reeds (I’m glad I did since I found a broken reed petal). I plan to lean it out a bit and will post what jetting specs worked.
Comments
Has this video helped you out? Please comment below.
Hey dude! love your vids! sadly ive got an CRF250R 09 🙁
can you upload a video how to clean your engine? mine is dirty and looks awful!
I would love to have more videos that can be used on other bikes, like how to tune jetting ect..
Greetings from Sweden!
// Dennis
Thanks for the compliment!
Clean your dirty bike/engine with a powerwasher. I have yet to purchase one myself. I do have a engine rebuild on a 07′ CRF250R in case you ever run into issues.
Do you have any uploads on a 1994 yz 250. Im having issues on adjusting the air mixture. 1st n 2nd gears are choppy on powerband butt through the rest of the gears it runs fine can you help.. Thanks.
Roy, I don’t have any vids on that specific model. Send me an email through my contact page and we can try and figure out whats wrong.
I got a kx 250 cant get it to run and the clutch is sleeping I’d k what to do because it won’t start
Perform a compression check:
https://howtomotorcyclerepair.com/how-to-kx250-compression-test/
Check for spark, and install a NEW plug.
Hi there. Great content. Thankyou. I have the ’05 KX 250 2 stroke. Gonna be checking out all your content. My carb needs float bowl & probably a jet block gaskett. I still need to check the Reed’s out. I don’t have V force or anything fancy, just standard reed cage. I may be able to upgrade to carbon petals soon. Only had the bike a short while
I have a 2001 kx250. The bike has been running rich. What do you recommend to lean out the fuel ratio?
Caleb,
I’m at 700ft altitude and ride in 70-80°F, 60-90% humidity and here is what I ended up jetting to:
48 pilot jet, air screw 1.25 out
NAFG needle 2nd clip position
158 main jet
Runs crisp and no spooge. No longer fouls plug.
At 23:57 you mention the white plastic piece needs to snap in, why is that? What would the be the result if not done?
Byron, “snap in” was probably the wrong term. The cable end and spring simply need to sit in the correct pockets.
Matthew need help have 2001kx250,piolet 48,main 152 needle naff 1/12 turns clip 1st groove, spooge and smoke but runs crisp, please help if you can on why it’s still so rich thanks buddy steven from sydney australia.
Try a larger (leaner) diameter needle like the NAFG.
I have a 2002 KX 250 I completely rebuild bottom up transmission bearings everything, had cylinder sent off and re- niksealed running rich spooling and fouling plugs every other tank of gas 40 to 1 benol 2 clip on needle air screw 2 turns out.
What is your current jetting? Stock?
Forgot to mention. The bike is running rich. Has a slight leak on the float bowl & spooge emanating from muffler when I ride. I meant carbono reed petals. It’s a product available here where I live in South Africa. V force or any such reed cages are too expensive for me now
Rebuild the carb, make sure reeds are fresh, before you start jetting it.