Cr250 keihin pwk flooding problems.

[Tory925]

Hi I just bought a used keihin pwk 38mm carb from a kx250 for my 2003 cr250. I took it all apart cleaned everything put new 42 pilot and 175 main jets and the needle on the #3 clip. I Tried starting the bike and it started but I just getting way to much fuel to where it's just bogging, blowing smoke, and barely running.

If I turn the gas to the off position on the bike right before it's ran out of fuel it starts running like a champ.

It sounds to me like a float hight problem but tried to adjust it and no change, but I really am not good with carbs.

Any help would be much appreciated.

[majikman808]

If it was your float it would either overflow and drain out the vent tubes or your bike would starve for fuel at wot. Is it running crappy at all throttle positions or just at idle? What is the air screw adjusted to?

[Tory925]

Ya it runs like crap the whole power band unless I turn the gas to all most all the way off then it runs strong. It just seems like gas is pouring into the carb.

[Tory925]

Oh ya I tried air screw all the way in/out no difference. Same with fuel screw.

[Curt026]

What needle is in the carb and did you block off the power jet circuit? Our bikes do not use the power jet that the yz and I believe the kx's use. I simply removed it and used a small threaded plug that has an allen head on it. They can be found at your local hardware store or Home Depot where I got mine. Sorry I do not remember the exact size. Or just jb weld it closed like a lot of people do. The pilot screw or 'air screw' should be between 1 to 3 turns out from full in. Turning it in, clockwise, will richen the circuit and out is leaner. This screw is called a 'fuel screw' in 4 stroke language. Sounds to me like you probably have a combination of all three of those issues.

[majikman808]

Oh wow! Maybe your float is to blame. Try check the float valve. Its a little aluminum piece with a rubber tip. Check for debris and float height. Make sure it closes before it reaches the top. Theres a measurment but i dont know it off the top of my head.

[Tory925]

Curt026 power jet what is that I don't know if mine has that. What does it look like?

[Tory925]

The float valve and floats are operating good new float valve and rebuild kit installed.

[majikman808]

On the pwk the black plastic screw on the side of the carb is the idle screw. The little brass screw just under the fuel inlet is the air screw. It should be between 1-3 out if its more than your pilot is too big. Do you have more pilot jets to try

[Tory925]

I have other Jett's but I can't even get it to run even half way right before it floods and just pours smoke. I think it has to be the float hight do you happen to know what the right hight for the pwk is?

[Kawabuggy]

Let's back up a step.. How was the engine running BEFORE you installed the carb? What's the history on the bike? Can you absolutely confirm that this is not an internal engine problem? Also, have you checked to make sure that the carb boots are tight and not allowing an air leak? Since you just put the carb on, and I know what a pain in the behind it is to get it stuffed in there, I want to be sure you don't have an air leak at one of the boots.

 

As a test, can you put the old carb back on and try to ride it to be sure it's actually the new carb causing the problems?

 

Your float height should be 16MM. Your rebuild kit should have had instructions that indicate how the float was to be adjusted. If you simply put in new floats, and new needle, but did not adjust the float height, then you need to go back in the carb and do that now before you do anything else. There is a very specific way that the float must be adjusted and it is in your owners manual, and should also have been in the instructions for your rebuild kit.

[Curt026]

I apologize, I just went back and read your first post again. I thought the carb was from a 2003 kx250 and didn't realize that your bike is a 2003. But to verify anyways does the new carb have any wires coming off of it for a TPS hookup? Your bike being a 2003 you need the old style pwk that has the twist on cap for the slide/throttle cable. The TPS version of the pwk carb are for the 04-07 cr's. Further more the old style pwk does not have a power jet circuit like the new ones do. So verify which style carb you have and go from there. Setting float height can be tricky. It is 16mm for the old style carbs and only 6-8mm for the TPS version. It can be difficult to do for your first time and I had a lot of trouble understanding the instructions I read online for how to do it so I set mine up an easier way. I simply attached a clean piece of clear hose to the fuel inlet supply (where your fuel line attaches to). Then blow in the line and work the float up and down. You should not be able to blow air through the line when it float becomes parallel to bottom of the carb. Look at the float and you will see a line where it looks the two halves are joined together. Make that line up with the carb bottom right as it shuts off the fuel. I found doing it this way much easier to figure out for the first time and then used it to determine how people come up with the 16mm measurements. I'm not good at explaining things in words so hopefully I didn't make that more confusing than it is.

[Tory925]

Hi guys so ya I have taken the pwk back off and put the tmx on and it runs perfect. The pwk is a twist top and does not have wires. I think it is the float hight so I will try the blowing the inlet hose and push the float to parallel next. When the level is right will I be able to blow and air through the hose?

[Kawabuggy]

Okay, to adjust the float height you will need to bend the tab that pushes against the needle while you are measuring the float height in regards to the carb body flat that the bowl attaches to.  You do not need to "I will try the blowing the inlet hose and push the float to parallel next" that you mention. Please buy and read a Honda service manual as it will detail what needs to be done. You can find a manual for a 2000 Honda CR250 on-line as it will have instructions for setting your float height on that PWK. As you may know all '01 & newer CR's had the TMX so a manual for those bikes will not have information on your PWK.

 

You do not ever need to "blow air through the hose" to set the floats. Do you have a friend, or family member, that is knowledgeable on working on bikes? At this point I can't stress enough that you need to ask for assistance from someone who knows what they are doing so that you can get this figured out quickly, and safely.

[Tory925]

Ok thanks for all the info I will report back after I try setting the float hight. Hopefully this pwk is worth all the trouble.

[Curt026]

http://m.youtube.com/watch?v=Kgog_Ng0-2Q#

http://m.youtube.com/watch?v=SiUDoXiPcKE#

Setting your floats the first time can be tricky if no one is able to explain exactly what you need to look for when doing it. The first video I posted will give you a good idea of what I was trying to explain and wil give you a good understanding of exactly what you trying to accomplish. The second video shows where your measuring from and should be similar eventhough its on a different carb version. Yes I agree that if you set your carb up the way the guy does in the first video it may not be exactly 16mm, but irregardless it will work. Setting float height is a very simple process, but it is hard to explain over the Internet and that's why so many people have a hard time understanding it. I'm sure I will get more crap for posting the first video and saying that if you follow that procedure that your bike will run fine, but I don't care. A running bike is better than what you have now. Get it working and then fine tune from there. Remember the float adjustment affects all circuits of the carb so if its not set right then jetting the rest of the carb is going to be impossible. Hope that gets you on the right track.

[223hpyhooker]

What year kx did the carb come off of.

[Beau 88]

I apologize, I just went back and read your first post again. I thought the carb was from a 2003 kx250 and didn't realize that your bike is a 2003. But to verify anyways does the new carb have any wires coming off of it for a TPS hookup? Your bike being a 2003 you need the old style pwk that has the twist on cap for the slide/throttle cable. The TPS version of the pwk carb are for the 04-07 cr's. Further more the old style pwk does not have a power jet circuit like the new ones do. So verify which style carb you have and go from there. Setting float height can be tricky. It is 16mm for the old style carbs and only 6-8mm for the TPS version. It can be difficult to do for your first time and I had a lot of trouble understanding the instructions I read online for how to do it so I set mine up an easier way. I simply attached a clean piece of clear hose to the fuel inlet supply (where your fuel line attaches to). Then blow in the line and work the float up and down. You should not be able to blow air through the line when it float becomes parallel to bottom of the carb. Look at the float and you will see a line where it looks the two halves are joined together. Make that line up with the carb bottom right as it shuts off the fuel. I found doing it this way much easier to figure out for the first time and then used it to determine how people come up with the 16mm measurements. I'm not good at explaining things in words so hopefully I didn't make that more confusing than it is.

Curt026 is correct if you can level the float with the bottom of the carb body, you can't just simply flip it upside down though . Hold it upside down at a 45 degree angle and watch as the metal tang ( for lack of better words ) touches the button on top of the float needle to push it against the seat . Just barely touching is where you wanna set it . Again with the float parallel with the carb body at the same time . After your running if you turn your air screw all the way in and it don't die you need a smaller pilot jet more than 3 turns out you need a larger pilot jet . That should get you in the ball park . 

[Tory925]

Thanks everyone I will try this and get back.

[Tory925]

Thanks everyone I will try this and get back.