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Keihin PWK 38 Air Striker on 02 CR250R - some questions

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So, I bought myself a Keihin PWK38 Air Striker this weekend :lol:

It's the older version PWK, with the 91.0mm body. Some pics:

DSC04366-1.jpg

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DSC04367-2.jpg

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Without inspecting it, I swapped it with the Mikuni. It fired right up, and it idled very nice. I didn't get far however, because I noticed jetting was way off (too rich), and the bottom overflow spit out fuel. I have some questions now:

- Jetting is 188 main, 42 pilot jet. I am at sea level, at about 50 degrees F. I'm guessing it is way too rich. How should I jet it? (to start with)

- I took off the float bowl and checked if the float valve worked correctly. One time fuel was cut off, another time it wasn't. What could this be? Dirt? Worn out float valve?

- The tip of the needle seems busted. What needle should I order? One for the 2000 CR250R carb?

- There's a small hole in the bottom of where the choke goes into. The OEM parts diagram (of a 2000 CR250R) shows a choke with a tip (which goes into the hole, but my choke doesn't have this tip. Should I order another choke?

Thanks in advance! :banana:

Edited by FrankV
added pic of the OEM choke

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In my 05 with the 38mm I think I was using a 175 main with a 45 pilot. Thats normal summer temps (65-90F) and elevation around 1000' ASL. Depending upon which needle you go with can make a difference on the mains & pilots.

The stock 2000 needle worked well in mine as well as the JD needles. In my 36mm keihin, the DDK works really well.

I dont remember seeing a "tip" on my choke.

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In my situation the CR250 needle (215-289R) was too lean mid throttle, but it might be different in your bike.

You could give it a try, try a 178 MJ, 50PJ, 2nd clip, 1 1/2 turns on A/S (that combo worked the best for me on the 215-289R needle).

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Thanks for the replies!

The current (busted) needle says "R1368DKA". I found this topic on TT which says that needle is a dual taper optional needle for the '99 CR250R (16201-KZ3-J11). I think I'll order one of these first (together with some jets) and see what happens :banana:

edit1: the number on the carb is 'PWK 00AAMG' - so it's a 1999 carb

edit2: the float height is set to 16.5 mm. Can someone confirm this is okay?

Edited by FrankV
added float height

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I think I remember hearing that the stock 1999 needle was a good choice.

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So, I put in the new '99 needle and installed the carb. 180 MJ, 48 PJ, needle 2nd clip (54 oF, sea level).

WOW! It runs really great. It start first kick (warm and cold), idles very nice and and has a really crisp response :thumbsup:

I had some spooge, checked the air screw (3 turns out best) so I installed a smaller 45 PJ (now 2 turns out). The spooge is gone, but it's still a bit 'smokey'.

I'll have to ride it first now, to make better adjustments (too wet right now).

Some questions:

- the carb is a bit longer and doesn't go into the intake rubber as far as the Mikuni went (see pic). Should I modify the rubber? The carb seems to be in there quite well

- it looks like it takes a bit longer to get back to idle. Is this due to the smaller PJ?

- I'm using 1:32 oil/fuel. Should I go up a bit more so is not that 'smokey' anymore?

DSC04383a.jpg

(large pic)

DSC04384a.jpg

(large pic)

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So, I put in the new '99 needle and installed the carb. 180 MJ, 48 PJ, needle 2nd clip (54 oF, sea level).

WOW! It runs really great. It start first kick (warm and cold), idles very nice and and has a really crisp response :thumbsup:

I had some spooge, checked the air screw (3 turns out best) so I installed a smaller 45 PJ (now 2 turns out). The spooge is gone, but it's still a bit 'smokey'.

I'll have to ride it first now, to make better adjustments (too wet right now).

Some questions:

- the carb is a bit longer and doesn't go into the intake rubber as far as the Mikuni went (see pic). Should I modify the rubber? The carb seems to be in there quite well

- it looks like it takes a bit longer to get back to idle. Is this due to the smaller PJ?

- I'm using 1:32 oil/fuel. Should I go up a bit more so is not that 'smokey' anymore?

-I have the 00 Kehin carb on my 02 frame with the 03 carb boot & fits really good. The 02 has more of an angle on the air boot.

- You can try turning the airscrew in (richer) a 1/8 at a time w/ the 45 pj till you get to 1 turn out if that doesn't solve your idle transition then try the needle in the 3rd clip pos(richer). Also check your throttle cable & make sure it's not snaged anywhere.

-I run 40:1 with good results.

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-I have the 00 Kehin carb on my 02 frame with the 03 carb boot & fits really good. The 02 has more of an angle on the air boot.

- You can try turning the airscrew in (richer) a 1/8 at a time w/ the 45 pj till you get to 1 turn out if that doesn't solve your idle transition then try the needle in the 3rd clip pos(richer). Also check your throttle cable & make sure it's not snaged anywhere.

-I run 40:1 with good results.

Thanks for your answers!

I thought both air boots were the same, but the Honda numbers are indeed slightly different. I'm gonna look for the 03 boot.

I also tried the 42 PJ, and I must say it goes back to idle very nice now, but I'm afraid this might be too lean... Or do only the MJ and needle clip position determine whether it's lean or not?

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Thanks for your answers!

I thought both air boots were the same, but the Honda numbers are indeed slightly different. I'm gonna look for the 03 boot.

I also tried the 42 PJ, and I must say it goes back to idle very nice now, but I'm afraid this might be too lean... Or do only the MJ and needle clip position determine whether it's lean or not?

1999 HONDA CR250

Jet...Stock...Recommended

MAIN...190...188

PILOT...42...45

NEEDLE...1370D...1369D

CLIP...3rd...1st

AIR SCREW...2 turns...2.5

As recommended by MXA for 92+ octane 32:1 mix ratio at sea level to ~1200 or so feet.

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Thanks for your answers!

I thought both air boots were the same, but the Honda numbers are indeed slightly different. I'm gonna look for the 03 boot.

I also tried the 42 PJ, and I must say it goes back to idle very nice now, but I'm afraid this might be too lean... Or do only the MJ and needle clip position determine whether it's lean or not?

That's odd.. normaly a hanging idle means a lean cond. & you went leaner on the PJ ??

This is how the carb jettting circuits function. You adjust your jetting depending on if your on the lean or rich side.

PJ & AS - off idle to about 1/4 throttle

Needle straight section - off idle to 1/4

Needle tapered section - 1/4 to 3/4 throttle

MJ - starts at about 1/2 to WOT

Clip pos. - 1st pos.= Leanest - 5th pos. = Richest

Clip pos. - From low to med. circuit

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Thanks, SubTexel! Looks like I'm on the lean side right now.

That's odd.. normaly a hanging idle means a lean cond. & you went leaner on the PJ ??

This is how the carb jettting circuits function. You adjust your jetting depending on if your on the lean or rich side.

Exactly, I knew that too... But I must say it's not a true hanging idle, I just noticed it went back to idle (even) nicer with the 42 PJ.

I think it's best to ride it first and see how she does, I'll let you know :thumbsup:

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