Jetting a 2-stroke carb (Keihin PWK)

Hey fellow riders!  I had to rejet the carb on my YZ85 for higher altitude today, and decided to take some pics  People are always asking about this step or that step - so I figured a pic was worth a thousand typo's!!

Although this is a YZ85 - the PWK carb on this bike is common to many Japanese 2-strokes, so the procedure will be similar, if not identical!  Enjoy..



These are the tools you will need.  6,8, 10mm wrench.  Ratchet driver, screw driver, 17mm wrench. And for supplies - jets of course!  This is my box of high altitude jets and needles.



This is the standard PWK carb used on many Japanese bikes. On it you can see the idle adjustment screw (black) and the airscrew to the right (brass). On either end of the carb there are clamps tha hold the carb on.  Loosen the screws on both sides of the carb, and the carb is then free to tilt.



I have rotated the bottom of the carb toward me for easier access to the float bowl, main jet, and pilot jet.



It's a good idea to put a rag under your carb to catch gas that might spill!



Remove the cap off the bottom of the carb with a 17mm wrench.  Some gas may come out. Once off, you can see the main jet in the middle and the small pilot jet to the side.  The main comes out by using a 6mmm socket, the pilot comes out with the help of a flathead screwdriver.



I have unscrewed the pilot. If you look closely you will see it is marked 42.  I need a 40 pilot for the altitude this bike will be running at, so I will replace this pilot with a 40.  The pilot simply screw into the bottom of the carb.  DON'T over tighten it!  Turn it finger tight with the screwdriver, and then an 1/8th turn more.



OK - done with installing the new pilot. If I needed to change the main, I would simply unscrew it from the center of the carb and then screw in the new one.  Same tightness as the pilot.



Here I have tilted the carb the other way so that I can gain access to the needle and slide. Remove the two screws on the top plate of the carb, and the top will come off.  Be careful not to scratch the slide or needle, or bend the needle when pulling the top of the carb out.




This is the slide assembly removed from the carb, You can clearly see the needle in the center of the slide.  If you push the needle up gently, the white plastic collar will come up and you can then remove the throttle cable from the slide.



This is the slide once it has been separated from the throttle cable.  The needle sumply comes out the top.



I am replacing this needle with a different taper needle.  However, sometimes you just need to change the clip position. This needle has the clip in position one.  If you needed it in position two, just remove the clip and move it down (toward the pointy end of the needle) one groove position.



The slide goes back together fairly easily. Put your needle in the center of the slide.  Then put the spring and white retainer on the throttle cable.  While compressing the spring against the top of the carb plate, insert the end of the cable back into the slide. You will see a groove in the slide that the cable end fits in.  Now release the spring and guide the white plastic retainer into the slide.  You've got it right when the white plastic covers the cable in the slide completely.
Now carefully slide the needle and slide assembly back into the top of the carb.  Be very gentle - don't force anything. When it's in, go ahead and put the 2 screws back in the top of the carb and tighten them - just snog, not too tight..



Turn the carb back into it's proper position. You will know it's in the right position when the metal tab lines up into the rubber groove as shown in the picture.



ALWAYS double check your hoses!  This one was pulled loose when rotating the carb.  It would have been easy to miss!  Check every hose and re-attach any loose or disconnected ones.




All done and ready to go!  Give the throttle a few quick blips to make sure that everything is operating smoothly.  Take a test ride around the block ans see how she goes!

It actually took me longer to type this post than it did to rejet the top and bottom of the carb

Skipper  
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Here we go again!

P.S.  Giving props where they are due.. I would NEVER have been able to do this without Woods' excellent tutorial on positng thubnail pictures.  Thanks Woods!!!

Skip  
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Here we go again!

Bump  

Bill H.
Temperance, Mi
2000 CR250R
1991 YZ125

Nicely done Skip! Those are restaurant quality pics, way better than any manual.  
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Nobody's gonna hurt anybody. We're gonna be like little Fonzies here. And what's Fonzie like? Come on what's Fonzie like?

Great step by step Skip! Now if we can get Dave to sticky it you won't have to repeat the proceedure for a billenth time. Thanks for taking the time.  
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DIABETES SUX!

..And more nutritious too, Chud!

Woods - I have faith Thanks!  
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Here we go again!

great job skip. Another one for my libary.  
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I love this dirt stuff.

Is my little thread not Sticky Worthy?  
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Here we go again!

It is on my computer. Ok where is DL?  
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I love this dirt stuff.

DL who?  
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DIABETES SUX!

Woods do you genuninely not know who DL is? or are you joking? lol

Oh and Skip, your little thread's been stickyfied! lol  
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The King Of Crumpets - Crumpet Boy!

- 1991 RM125

Mmmm.. loving the stickiness!  Thanks DL!  
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Here we go again!

Does it feel good Skip?? :P lol  
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The King Of Crumpets - Crumpet Boy!

- 1991 RM125

Very informative thanks ... Nice stand btw looks like mine hehe    
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05 KTM 125 SX

good job  
-1998 cr125
Kermaxx Fat bars
one white plastics
factory effects graphics
fmf fatty
renthal chain and sproket
Brand new carlsbads
excel rims.
and one bad ass rider