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New Carb suggestions? 94 YZ250

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Howdy,

I've decided to put a new carb on the YZ. I was just going to replace it with the OEM-equivalent carb: Mikuni TM38... are there any other carbs I should look into? Something more contemporary?

Thanks

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Why are you replacing the carb?

If I were replacing a Mikuni, I would go with a Keihin PWK. I think the PWK is a better carb.

I've heard some interesting things about the Lectron HVPJ, but I don't know anybody that has one, and I've always been pretty happy with the Keihin so no desire on my part to experiment.

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I'm replacing it just because it's sloppy: stripped threads, gouges from screwdrivers, dings, and whatnot. Slide is worn/dinged, etc. It works, I just want to put a fresh one on there.

Also, what is the "Spigot size" referring to? When choosing a carb, I need to select a bore and a spigot size.

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Ok Chokey, I did some quick research on the PWK38... it does seem to be superior to the Mikunis.

Which one exactly am I looking for? screw top, flat top, certain year of YZ or other, etc? It seems like there are some variations over years/applications.

Thanks

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Keep in mind, jetting is going to be trial-and-error unless you know somebody that has done this swap. It could get expensive if you end up needing to swap slides to get the jetting right.

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Thanks. So you're saying this is a bolt on and ride application? Dial in the pilot, needle, and main jet, then I'm a happy camper? Sweet.

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Physically it's a bolt-on, with the possible exception of the throttle cable connection. I haven't had a YZ two-stroke since 1986, so I don't know what issues you may run into with that.

As for jetting, as long as the slide you order with the carb is right, it's fairly straightforward to get the jetting right, although it can be a bit time consuming.

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Physically it's a bolt-on, with the possible exception of the throttle cable connection. I haven't had a YZ two-stroke since 1986, so I don't know what issues you may run into with that.

As for jetting, as long as the slide you order with the carb is right, it's fairly straightforward to get the jetting right, although it can be a bit time consuming.

Thanks. I've got jetting procedures figured out. Need to look into the slide and throttle cable connector type next.

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If I were replacing a Mikuni, I would go with a Keihin PWK. I think the PWK is a better carb.

That was going to be my suggestion as well.

The latest YZs (my 2002 and my 2010) all have the fully electronic Keihin... I'll bet the cables, slides and keepers are similar if not the same between the later carbs and that screw-top keihin. So if your stock older stuff doesn't work with the Keihin you could swap to a later YZ throttle cable (1999-2012 would probably do the trick).

Back in 1998 I bought a CR250R... It had the powerjet Keihin without the TPS. If memory serves me correctly, the 1999 CR250R had the same carb without the powerjet. I think the 1999 - 2001 CR250R had zero electronics like the carb in Chokey's photo above. So that may be a good application to start with if later YZ parts don't do the trick.

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Look for the PWK "Airstriker" 38mm (non electronic)--much better carb than the standard PWK. It came stock on the 2000 Honda CR250--maybe some late model 99s. I don't know about the physical dimensions vs. the standard PWK but it can be fitted to your bike. I fitted it to my 94 yz motor in my 97WR250.

Do a search here--there was a real good write up on a WR250 a while back with this exact swap.:lol:

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Look for the PWK "Airstriker" 38mm (non electronic)--much better carb than the standard PWK. It came stock on the 2000 Honda CR250--maybe some late model 99s. I don't know about the physical dimensions vs. the standard PWK but it can be fitted to your bike. I fitted it to my 94 yz motor in my 97WR250.

Do a search here--there was a real good write up on a WR250 a while back with this exact swap.:lol:

I'm still dubious as to the benefits of the Air Striker. I've heard some people rave about it, and others say they never could make it run right. But I have no personal experience with them to say one way or the other.

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I'm still dubious as to the benefits of the Air Striker. I've heard some people rave about it, and others say they never could make it run right. But I have no personal experience with them to say one way or the other.

Didn't the 02' KX 250 come stock with an air striker?

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No, it has a PWK38S with Powerjet and TPS.

Isn't the difference between a standard and a air striker pwk the 2 vanes that are cast into the inlet bell of the air striker? Are you saying your power jet/TPS PWK carb doesn't have those 2 vanes?

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All PWK carbs have small wings inside the inlet for low-speed air control. It's one of the primary differences between the PWK and the PWM series.

Uh, the PWK you posted on the 1st page doesn't have the vanes????

pwk41.jpg

So what is the difference between a regular PWK and a PWK-Air Striker?

I was under the impression that the PWK-38S (Shorty) that comes on all the newer YZ/RM/KX 250's is a PWK-AirStriker-quad vent and then with the PJ and TPS ?????

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