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Keihin PWK 28 carb for my CRF 230?

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So I was a little bored so I thought I'd try another carb. I know a few of you were running a Keihin PWK 28 carb. Anyone want to share some jetting info? I wasn't sure what jet sizes I would start with.

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Got a 2004 30 mm XR250 carb on mine. Why spend that much $ on just 2 mm larger?

I got a 150f with a 32 mm flat slide from EO and it pulls harder than any of my three bikes from the bottom to the top.

If you want max torque, just leave the stock 26mm carb on it.

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So I was a little bored so I thought I'd try another carb. I know a few of you were running a Keihin PWK 28 carb. Anyone want to share some jetting info? I wasn't sure what jet sizes I would start with.

 

An awesome performance carburetor. Adds a lot to the 230. The underside of the slide is manufactured to pull fuel from the needle jet very early. Made to increase torque in two strokes it comes with a bleed type needle jet which is what all four stokes should have.

 

Now about those jetting specs. I just came back from a vacation and looked for my PWK jet box that has the specs. Gotta look again tonight or tomorrow. When found I will PM you.

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Hello guys.

I did not know the pwk 28 keihin carburetor for the crf230.

I tried on-line and I found very interesting information.

In addition the pwk 28 (See first picture please) I also found the keihin pwk 29 rr, which seems to be an evolution of the pwk 28.

Perhaps the pwk 29 rr carburetor is more similar to the processed carburetor that we find in the manual?( second picture).

Each advice is well accepted.

Hello to all From Italy

http://carburetor-online.com/racing_scooter_keihin_pwk_29_rr_carburetor.html

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1401201167838.jpg

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An awesome performance carburetor. Adds a lot to the 230. The underside of the slide is manufactured to pull fuel from the needle jet very early. Made to increase torque in two strokes it comes with a bleed type needle jet which is what all four stokes should have.

 

Now about those jetting specs. I just came back from a vacation and looked for my PWK jet box that has the specs. Gotta look again tonight or tomorrow. When found I will PM you.

Oh goodie!  Thanks Stevethe.  If you could share that info, this might be a fun project.

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Hello guys.

I did not know the pwk 28 keihin carburetor for the crf230.

I tried on-line and I found very interesting information.

In addition the pwk 28 (See first picture please) I also found the keihin pwk 29 rr, which seems to be an evolution of the pwk 28.

Perhaps the pwk 29 rr carburetor is more similar to the processed carburetor that we find in the manual?( second picture).

Each advice is well accepted.

Hello to all From Italy

http://carburetor-online.com/racing_scooter_keihin_pwk_29_rr_carburetor.html

 

Wow crossplayer, nice stuff. I had to bore mine larger.

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Now about those jetting specs. I just came back from a vacation and looked for my PWK jet box that has the specs. Gotta look again tonight or tomorrow. When found I will PM you.

I have a PWK 28 that's just sitting on the shelf that I'd like to try on the 230F.

Please share your jetting specs w/ us. Much appreciated!

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Oh my, such fun is about to begin!
I also have a PWK  that was planned for a 2T case reed engine, and I'm in need of better carburation on my XR218.
What I'm particular interested in are the content specs for the carb in the post #5 link.

Going back over my notes I found:
 
Carb………. Inlet Bell.. Outlet OD…. Outlet ID…. LOA
PD 97A………. 43.65………. na…….…. 29.7………. 79.9.... 86+ XR200R carb, same body as other 185/200 two valve motors
PD05A…….…. 46.9………. 39.9…….…. 33.8………. 96.8..  body is used on XR250R and CRF230F
BSR32……..…. 52.1………. 38……..…. 31.8………. 88.4.... a CV carb from a GZ250
BST31……..…. 50.2………. 39.9……..…. 30.7…..…. 93...... a CV carb from a DR200
PHBL………... 39.9…….…. 30.95….…………….….. 90.4..... Delorto carb used on some 2T Trials bikes
PWK28………. 49.6…….…. 34.85…….. 28.5…...….. 83.2.... Keihin 2T mini MX carb
Mikuni 30mm…. 44………………………...29.2….……......... used on some Powroll engines
 
So a modded CRF230F manifold will accept a PWK 28/29 carb, and the 230 air boot should stretch enough to fit the inlet bell. The 230F manifold bolts to the 185/200 heads but the carb angle is a bit different than the 86+ XR200 manifold, wasn't a problem for my CV carb conversion.

And for you  owners of late XR200 just use the 86-95 XR250 air boot (bolt pattern on air box is different but just a minor details!), or use a XR250 airbox and boot.

 

Need a cheap source for PWK slides.

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THX for posting up the chart. Dimensions are always helpful.

 

So a modded CRF230F manifold will accept a PWK 28/29 carb, and the 230 air boot should stretch enough to fit the inlet bell.

 

So per your chart above, the outlet of the stock carb (PD05a) is ~5mm larger than the PWK28, correct?

IF so, can't the stock manifold be clamped down enough to seal over the PWK's 35mm outlet dia, or is this too much drop in diameter to do so?

 

 



 
Edited by jeddclampette

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Hello guys ..

Since we're talking about carbs I would like to ask a question.

In my crf230 Italian version is installed oem Keihin PD 9 CA. (picture 1).

The PD 9 CA hole (picture 2) is smaller and decentralised than xr 250 carb hole (Figure 3).

I would try to mill the crf230 carb hole as the xr250 carb hole. Someone has already done this and can give advice?

Thanks

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Hello guys ..

Since we're talking about carbs I would like to ask a question.

In my crf230 Italian version is installed oem Keihin PD 9 CA. (picture 1).

The PD 9 CA hole (picture 2) is smaller and decentralised than xr 250 carb hole (Figure 3).

I would try to mill the crf230 carb hole as the xr250 carb hole. Someone has already done this and can give advice?

Thanks

 

Yes this has been done by a few here with success.  You must also bore the intake manifold to match.

 

See here:  http://www.thumpertalk.com/topic/858669-cheap-hp-for-230-but-no-one-talks-about-it/

 

And here:  http://www.thumpertalk.com/topic/826118-cheaper-and-easier-than-xr-carb/

 

I have been considering boring mine from 26mm to 28mm.  That would be approximately 7.7% more area.  A 30mm bore would be approximately 15.4% more area.  See below for more options:

27mm = 3.9% more area

28mm = 7.7% more area

29mm = 9.7% more area

30mm = 15.4% more area

 

I ran an XR250 carb on my CRF230 for a test and I didn't care for it.  It gained some mid and mid-top but it lost the off-idle and low-mid I really need for the type of riding I do.  It changed the sound of the exhaust as well.  See here:  http://www.thumpertalk.com/topic/816822-mike-coe-jetting-versus-xr250-carb-results/

 

I think a 28mm bore would be a very good compromise.

Edited by VortecCPI

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Thanks VortecCPI.

The Italian version has 28 mm stock ..

I was thinking of milling only the upper part of the hole does not change off-idle and low-mid,

because I also I need this for the type of riding.

The area will be increased only at the maximum throttle opening .. what do you think of this?

(For your information I have to start by saying that my crf230 is modded.

I have a 10.5:1 67mm Wossener piston + Grind #: 282 Webcam (bolt in) + Snorkel removed and modded muffler. 120 Main jet + 45 pilot and needle to the fourth notch from above.)

Sorry for my english

Edited by Crossplayer

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Yes this has been done by a few here with success.  You must also bore the intake manifold to match.

 

See here:  http://www.thumpertalk.com/topic/858669-cheap-hp-for-230-but-no-one-talks-about-it/

 

And here:  http://www.thumpertalk.com/topic/826118-cheaper-and-easier-than-xr-carb/

 

 

VortecCPI,

 

 

I read those post and I think I missed something.  Which side of the carb did they suggest to bore?  The side that goes to the air filter or the side that goes to the cylinder?  I would think it would be the air filter side, but then again, I could have understood it wrong.

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VortecCPI,

 

 

I read those post and I think I missed something.  Which side of the carb did they suggest to bore?  The side that goes to the air filter or the side that goes to the cylinder?  I would think it would be the air filter side, but then again, I could have understood it wrong.

 

They are boring the engine side.  The air cleaner side is the exact same on the XR250 carb.

 

On the left is my stock CRF230 carb.  On the right is a late-model XR250 carb.

0320101121a.jpg

0320101121b.jpg

Edited by VortecCPI

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They are boring the engine side.  The air cleaner side is the exact same on the XR250 carb.

 

On the left is my stock CRF230 carb.  On the right is a late-model XR250 carb.

Thanks Vortec.  From looking at it, that was what I thought, but like I said, I must have read that wrong.  thanks.

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I believe that My 2004 XR250 carb is larger on the intake side, the engine side and has a larger diameter slide as well. (Will check it out closer next time I have it off)

In the photos, there is a much larger gap above the choke shaft on the 30 mm carb than the 26mm

I for sure do not have any loss of off idle torque with the 30 mm carb since I added the ProCom.

As you may remember, I lost all my off Idle torque when I replaced my 40mc/402 cam with an 89a.

Trying to find my low end torque:

I then re-installed the stock carb (intake manifold matched to intake port and carb, and properly jetted for my application)

(with the stock carb back on)

The bike felt positively anemic, felt the same off idle but felt like I lost major power from approx 3,000 rpm and up.

I again reinstalled the 30mm carb after I installed the ProCom. And all my low end grunt is back as well as my normal midrange power as well.

Several years ago:

When I first installed my 30mm carb, on my then BBR 170cc 150f, it made more power every where, but the most pronounced thing that I noticed Immediately was that the RPM's would easily go right to the (stock) limiter much faster than before.

I had a BBR 26mm XR200r carb before that.

I had never ridden the bike at the limiter in the past and with the 30mm carb, I had to learn to short shift the bike to keep it off the limiter.

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Interesting Adnohguy,

 

You're a fan of the Procom CDI also. Well, after I make a few changes maybe I'll look into that also.  I'm not looking for lows at all. I have too many lows.  I want to trade that low end in for more top end, hence the carb change.  Well, one thing at a time.

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Interesting Adnohguy,

 

You're a fan of the Procom CDI also. Well, after I make a few changes maybe I'll look into that also.  I'm not looking for lows at all. I have too many lows.  I want to trade that low end in for more top end, hence the carb change.  Well, one thing at a time.

 

Hum well don't be surprised if you get more off the bottom with a PWK carb. 

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THX for posting up the chart. Dimensions are always helpful.

 

So per your chart above, the outlet of the stock carb (PD05a) is ~5mm larger than the PWK28, correct?

IF so, can't the stock manifold be clamped down enough to seal over the PWK's 35mm outlet dia, or is this too much drop in diameter to do so?

 

 

Probably, or wrap a few layers of electrical compound tape onto the carb, the electrical compound is stretchy rubber tape (not vinyl).  I've found the best compound, and vinyl, tapes at electrical suppliers for the trades.

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