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PWK Airstriker Swap 2005 CR250R

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I just ditched my phat TMX carb and installed a new Airstriker along with a Vforce3 reed valve.

The Airstriker has the JD jet kit pre-installed in it.

BIG DIFFERENCE.

Took the bike to the sand dunes today. Here's a quick report:

Instant throttle response. Very crisp and quick. No lag.

Slightly soft in the midrange.

HUGE hit on the top of the powerband.

Power delivery on this bike was smooth before the mods.

Some spooge out the exhaust.

A little hesitation off idle, strong mid, and smooth hit on top.

After the mods:

Instant throttle response. Smooth in the middle, HARD hit on the top-end.

Much stronger on the top now. Front wheel likes to pop up.

Just a hint of exhaust spooge. Much cleaner now.

I am happy with the mods. Carb and reed valve really woke this bike up.

PWK_5133.jpg

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I actually just started a thread over on allthingsmoto asking why everyone is going with these air striker carbs.

I have a 98 cr250 and it has the PJ 28 L carb with that power jet solenoid that is electrical. I don't even really dislike my carb on the bike now, but I just keep hearing that this air striker is such a nice upgrade...I'm really new to these 2 stroke motors and carbs though so I'd need to be explained about like a retard...Either way, doing a top end and new reeds for christmas, so I might look at getting a airstriker as well...Where did you buy it? And feel free to highlight or explain anything else! Thanks for posting this though.

Griffin

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What's the temp there in AZ now? Running stock TMX here and all's well (matches your after mods description) except right off idle. Gonna swap out my lean S7 back to S9 and see. If not will richen pilot to rid idle lean surge. Temp here is 30-39* now. Spooge free however. :lol:

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Temp at my riding spot is usually around 70F or so.

I bought the Airstriker from the JDjetting website. Fast shipping. Good service.

I asked a few questions via email before I ordered it, and James answered my questions promptly.

From what I have been reading, the stock TMX carb is really picky to try and jet correctly.

And the settings can change, so it's hard to keep it dialed-in.

People are going to the Airstriker because it's more of a "bolt-on and forget" mod.

It comes with a JD jet kit preinstalled, so it's really close right out of the box.

If you don't want to spend time fooling around trying to get the TMX dialed-in, go with the Airstriker.

It's worth it.

You don't need the TPS, you just unplug it, and remove the old carb.

New Airstriker has no TPS. You don't need it.

Stock throttle cable works fine.

A little tricky to get the airboot on it, because it's a little longer.

Also, I found the inlet nipple to be slightly smaller in diameter, so I had to use a new piece of fuel line, and a corbin clamp.

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Running stock TMX here and all's well (matches your after mods description) except right off idle.

Yeah, the off-idle hesitation is one of the problems with that TMX.

You must have yours jetted pretty close.

Did you put a JD kit in it?

I almost went that route... but decided to do the Airstriker.

Stock TMX is really rich. Mine was stock. I didn't feel like messing with it.

I did a Vforce3 reed valve at the same time I did the carb swap.

So not sure how much I gained from the carb vs the reed valve.

All I know is.... the motor feels stronger, and NO hesitation off idle.

It used to be smooth and flat on the top-end, but not anymore.

Pulls HARD on top now.

:lol:

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Yeah, the off-idle hesitation is one of the problems with that TMX.

You must have yours jetted pretty close.

Did you put a JD kit in it?

I almost went that route... but decided to do the Airstriker.

Stock TMX is really rich. Mine was stock. I didn't feel like messing with it.

I did a Vforce3 reed valve at the same time I did the carb swap.

So not sure how much I gained from the carb vs the reed valve.

All I know is.... the motor feels stronger, and NO hesitation off idle.

It used to be smooth and flat on the top-end, but not anymore.

Pulls HARD on top now.

:lol:

I gots the lean surge at idle regardless of air screw setting. Even went in as far as 3/4 or 1/2 turn where it just gurgled coz it was too rich but as soon as you'd try and have it idle it would keep surging. :)

The cost of the jetted PWK is about the same as a pipe.

No jd kit here yet.

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I have an '02 and an '03 CR250. Fooled with stock jets for a while. Gave up and bought the JD jet kits. Very nice improvement but I couldn't keep the bikes running crisp without re-jetting for every little weather change. Finally switched to Air Strikers and have been kicking myself for not making the swap years sooner.

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This is one of the best upgades you can do to the 02-07 CR 250's. The case reed motor cr250's might have won some shootouts had they come with the kehin carb from the factory. It gives it the off idle response & consistent jetting that the mikuni can't.

The midrange is one of the strongest areas of the these motors. I'd try the needle 1 clip richer & see if you can get a stronger pull in the mid.

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I actually just started a thread over on allthingsmoto asking why everyone is going with these air striker carbs.

I have a 98 cr250 and it has the PJ 28 L carb with that power jet solenoid that is electrical. I don't even really dislike my carb on the bike now, but I just keep hearing that this air striker is such a nice upgrade...I'm really new to these 2 stroke motors and carbs though so I'd need to be explained about like a retard...Either way, doing a top end and new reeds for christmas, so I might look at getting a airstriker as well...Where did you buy it? And feel free to highlight or explain anything else! Thanks for posting this though.

Griffin

The Keihin PWK is a nice upgrade over the Mikuni TMX, but it isn't much of an upgrade over the Keihin PJ (what you have). I would spend the money somewhere else if I were you.

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Yea, I remembered that lean surge madness when I first bought my '05 back in '06. Drove me nuts trying to cure it using the stock needle & stock pilot. But unlike most here, I was 100% satisfied w/ the TMX carb & JD kit for 2 solid yrs before replacing it w/ the PWK carb. Only reason I did the PWK swap was b/c so many here said to do it, and I had 3 spare PWKs (39, 38 & 36) on the shelf from my prior KTM days. Peer pressure...:lol:

Imho, it's a very decent carb, the TMX w/ TPS, but you need to plan on rejetting it from the stock settings. One advice I can throw out w/ the JD kit the 2005-07 CR2 is that the provided 31.5 pilot in the JD kit may be too rich for summers. I had to get a 30 pilot outside of the kit. Plus, when going from summer to winter, I had to replace the red JD needle w/ the blue, and then move the clip one position off from that of the red, making the needle change be an effective 1.5 clip change (vs. just a clip change for the PWK). No spooge when it's jetted right, and when I start to see spooge, that's when I know to plan on a pilot change between seasons.

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Great info guys, thanks for all the feedback.

Quick question... what does the airscrew affect?

JD sets it to 1 1/2 turns out. That is where it is at right now.

If I mess with it, what exactly does it affect?

This carb has an idle speed screw, so I assume that little brass-colored

air screw adjusts low speed mixture or something?

I'm not too experienced with trying to tune these carbs, so any info is appreciated.

Just trying to get it to run as good as it can.

:lol:

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Great info guys, thanks for all the feedback.

Quick question... what does the airscrew affect?

JD sets it to 1 1/2 turns out. That is where it is at right now.

If I mess with it, what exactly does it affect?

This carb has an idle speed screw, so I assume that little brass-colored

air screw adjusts low speed mixture or something?

I'm not too experienced with trying to tune these carbs, so any info is appreciated.

Just trying to get it to run as good as it can.

:lol:

http://www.thumpertalk.com/forum/showthread.php?t=412662

This thread gives you great info on setting up each jetting circuit.

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Great info guys, thanks for all the feedback.

Quick question... what does the airscrew affect?

JD sets it to 1 1/2 turns out. That is where it is at right now.

If I mess with it, what exactly does it affect?

This carb has an idle speed screw, so I assume that little brass-colored

air screw adjusts low speed mixture or something?

I'm not too experienced with trying to tune these carbs, so any info is appreciated.

Just trying to get it to run as good as it can.

:lol:

the air screw and pilot work together. its pretty much a starting and idle circuit.

you know when you let your bike idle and you stab the throttle WOT and the engine cuts out for a second then revs up? thats lean on the pilot. loading up and gurgling when you stab it open is rich. you can test this theory by setting your air screw way out and stab the throttle and vice versa. just a note, doing this on the stand is a good way to check but doesnt fully transfer into how the bike reacts under a load.

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Ah, ok. Makes sense.

Bike idles good, and when I snap the throttle open, it doesn't cut out or gurgle.

It snaps to attention, so I must be pretty close on my jettings and settings!

( Thanks to James Dean of course. )

:lol:

Thanks for the info!

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Just a quick question to everyone who has made the swap:

Do you tell them your specs (Bike, Mods, Altitude, etc.) and they install generally close jets, ship it to you, and you just bolt it on???

I am considering the swap for my stock 2006 CR250, even tho it runs decent with the Mikuni.....

I am just confused as to how everyone seems to just slap it on and go.

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Just a quick question to everyone who has made the swap:

Do you tell them your specs (Bike, Mods, Altitude, etc.) and they install generally close jets, ship it to you, and you just bolt it on???

I am considering the swap for my stock 2006 CR250, even tho it runs decent with the Mikuni.....

I am just confused as to how everyone seems to just slap it on and go.

All I did was tell JD Jetting what bikes they were going on ('02 CR250 and '03 CR250) and altitude where I live / ride (Louisiana - sea level to 300'). All I had to do with both bikes was set the idle speed.

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Thanks David, i was thinking thats how it worked, but wanted to confirm.

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That's weird though only altitude matters not temperature?? I know my main is changed 1 size if below or above 60 degrees....hmm

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That's weird though only altitude matters not temperature?? I know my main is changed 1 size if below or above 60 degrees....hmm

May need to do that if I ever ride them in cold weather. So far we haven't ridden either of them when the temperature was below about 65°. From 65° to 95° the jetting has been good.

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