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2004 CR250 Jetting and Needle

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Trying to help my buddy out. I feel like I’m pretty good with jetting because I own Yamaha’s and KTM. But I’m not that great with Mikuni. The bike has always put out some serious spoog. All over the swing arm etc. he told me the needle was was at the top

Clip. Anyways we have been dropping the Pj down to a 25.5 and still get a lot of spoog. Still on the swing arm. We ride from around 4500 to 8k... anyways he was mentioning that it had this performance Honda needle in it... so I finally broke into to take a look at this needle... WTF this needle is. I wish I took a picture of it. Trying to describe it, the body tapers down but the last 1/2 inch... it tapers down to like size of a paper clip. I have never seen anything like it... no freaking wonder I can’t get the spoog out of this bike. This needle is waaaaaay rich down low.

 

Can anybody give me a part # for a better working needle?

 

Also could I use the 18 KTM needle? Since they have all gone to Mukini.

 

 I’ve also heard the YZ125 is a great needle since it uses Mukini. Anybody tried it?

 

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10 hours ago, RMK800 said:

Trying to help my buddy out. I feel like I’m pretty good with jetting because I own Yamaha’s and KTM. But I’m not that great with Mikuni. The bike has always put out some serious spoog. All over the swing arm etc. he told me the needle was was at the top

Clip. Anyways we have been dropping the Pj down to a 25.5 and still get a lot of spoog. Still on the swing arm. We ride from around 4500 to 8k... anyways he was mentioning that it had this performance Honda needle in it... so I finally broke into to take a look at this needle... WTF this needle is. I wish I took a picture of it. Trying to describe it, the body tapers down but the last 1/2 inch... it tapers down to like size of a paper clip. I have never seen anything like it... no freaking wonder I can’t get the spoog out of this bike. This needle is waaaaaay rich down low.

 

Can anybody give me a part # for a better working needle?

 

Also could I use the 18 KTM needle? Since they have all gone to Mukini.

 

 I’ve also heard the YZ125 is a great needle since it uses Mukini. Anybody tried it?

 

Read my jetting thread.  Hopefully I can get some results soon and update.

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It looks like you might be a bit before testing. I just find it odd that there isn’t a huge forum on jetting. I think everybody has dumped the Mikuni.

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On 7/8/2018 at 1:03 AM, RMK800 said:

Trying to help my buddy out. I feel like I’m pretty good with jetting because I own Yamaha’s and KTM. But I’m not that great with Mikuni. The bike has always put out some serious spoog. All over the swing arm etc. he told me the needle was was at the top

Clip. Anyways we have been dropping the Pj down to a 25.5 and still get a lot of spoog. Still on the swing arm. We ride from around 4500 to 8k... anyways he was mentioning that it had this performance Honda needle in it... so I finally broke into to take a look at this needle... WTF this needle is. I wish I took a picture of it. Trying to describe it, the body tapers down but the last 1/2 inch... it tapers down to like size of a paper clip. I have never seen anything like it... no freaking wonder I can’t get the spoog out of this bike. This needle is waaaaaay rich down low.

 

Can anybody give me a part # for a better working needle?

 

Also could I use the 18 KTM needle? Since they have all gone to Mukini.

 

 I’ve also heard the YZ125 is a great needle since it uses Mukini. Anybody tried it?

 

What is this needle? Do you have a part number? https://www.procircuit.com/jettingspecs3.htm

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1 hour ago, RMK800 said:

 I think everybody has dumped the Mikuni.

Which is why your starting to see all the "How do I jet my Keihin" threads. If you can't jet the mikuni then how are you going to jet the keihin or any other carb?

 

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Which is why your starting to see all the "How do I jet my Keihin" threads. If you can't jet the mikuni then how are you going to jet the keihin or any other carb?

 

 

 

 

 

 

I think it’s what you are familiar with. Every bike that uses a Keihin are fairly close.

 

For example my YZ 250x is a mj 168, 42 pilot and #2 clip.

 

My sons Ktm 150sx is a 168mj, 38 pilot and #2 clip.

 

My sons ktm 85 is 115 mj 42 pilot and #2 clip.

 

My neighbors gas gas 200 is 168 mj,40 Pilot and #2....

 

Anyways that 3 different bikes and their similar in jetting. I just don’t have the experience with a Mikuni. I’m using a zuk needle in my X and a JD in the 150sx... even though those are two different needles. The #2 slot is best for my elevation out here.

 

Some ktm guys are dumping the mikuni for the Keihin because they gain some Hp and throttle response. I wonder how different a hondA Mikuni vs a KTM is... anyways, I’ll keep working at it.

 

A question for you, are the Keihin and Mikuni needles different length? Are they interchangeable at all?

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4 hours ago, RMK800 said:

It looks like you might be a bit before testing. I just find it odd that there isn’t a huge forum on jetting. I think everybody has dumped the Mikuni.

Don't worry, I'll have my bike back on the track very soon and then I'll get some JD testing results updated on my thread for you.  Lots of good reviews so fingers crossed.

 

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Ok here is the needle. The bike actually runs really good. Trying to reduce the spoog. We run 50:1 Amsoil Interceptor.

 

Going down one more on pilot. If that doesn’t help, will change needles. We are already at a top clip on needle.

 

You can see the last part is very thin.

 

Needle # 6DGY27-67

 

IMG_2881.thumb.JPG.21ded3b761ae7031869fd193c2abff4b.JPG

 

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From the look of that needle I would say the pilot jet isn't the problem. That needle is way too rich right from the start. Go back to the stock needle 6CHY12-82. I bet that spooge clears up. Pro Circuit recommends 400 main, 32.5 pilot, 6CHY12-82 needle, 2nd clip position, 1.25 open on the air screw. Bet that gets you pretty close. And at your riding elevations you could even drop one size on the pilot and main. Wouldn't be surprised if a 30 pilot is too big.

Edited by Keith72

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2 hours ago, RMK800 said:

Ok here is the needle. The bike actually runs really good. Trying to reduce the spoog. We run 50:1 Amsoil Interceptor.

 

Going down one more on pilot. If that doesn’t help, will change needles. We are already at a top clip on needle.

 

You can see the last part is very thin.

 

Needle # 6DGY27-67

 

IMG_2881.thumb.JPG.21ded3b761ae7031869fd193c2abff4b.JPG

 

 

If you’re curious here’s what the JD needles look like.  Notice the difference in the taper design, it has a more uniform change in diameter and has an overall wider diameter particularly towards the bottom or the “usable” portion that does more of the fuel flow control.  Also the tip design has a different angle on it.  Seems obvious to me this should help lean the bike out.  Not only that but also the recommended pilot is much smaller than any other recommendation I’ve seen yet.

9CDF5B95-A652-40B3-B2CB-CB8F5FC9DE14.jpeg

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If you’re curious here’s what the JD needles look like.  Notice the difference in the taper design, it has a more uniform change in diameter and has an overall wider diameter particularly towards the bottom or the “usable” portion that does more of the fuel flow control.  Also the tip design has a different angle on it.  Seems obvious to me this should help lean the bike out.  Not only that but also the recommended pilot is much smaller than any other recommendation I’ve seen yet.
9CDF5B95-A652-40B3-B2CB-CB8F5FC9DE14.thumb.jpeg.204b9b99ce9f0b2451ca2d1e89819372.jpeg



Thank you for showing me that. I can see that JD is a leaner needle. Would you mind measuring the needle and tell me how long it is?

I’m curious if Mikuni needles are really about 1/2 inch longer then Keihin needles.

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10 hours ago, RMK800 said:

 

 


Thank you for showing me that. I can see that JD is a leaner needle. Would you mind measuring the needle and tell me how long it is?

I’m curious if Mikuni needles are really about 1/2 inch longer then Keihin needles.

 

 

The battery in my caliper just faded to nothing, but these pictures should help.

Length eyeballing it on the scale looks close to 2.73” (69.2 mm). From the way all three needles look next to each other and how they all fit in the caliper I’m calling all three the same length.

I’ll take some diameter readings for you when I get a new battery for this thing.

 

C9A6D43D-C08F-4B3F-AE55-84945DBF4314.jpeg

240FFF61-C4B2-4199-AEE7-3663936EE1DE.jpeg

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Just an FYI.  I wouldn't use a 125 needle in a 250 because the 125 needles will be much richer than a 250 needle.  Second, the Keihin PWK needles are not compatible with the Mikuni carbs.  IMO, take Keith's advice and get the stock needle back in that carb, or go with the one step leaner needle for your model year 250 (I don't know what that would be but a honda dealer should be able to let you know, or the service manual probably could tell you).

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On 7/11/2018 at 7:33 AM, RMK800 said:

 

 


Thank you for showing me that. I can see that JD is a leaner needle. Would you mind measuring the needle and tell me how long it is?

I’m curious if Mikuni needles are really about 1/2 inch longer then Keihin needles.

 

 

As promised:

 

0A12B0CF-547F-40D3-BB79-36C9CB63860B.jpeg

72126349-C125-4937-850F-9F8D480C182F.jpeg

866B4A96-C9B1-44A4-BEBE-DFF78605CF33.jpeg

BA58762C-FEB7-4EE8-9675-F5B8667A4BEB.jpeg

C815FD01-E518-43CF-B46F-391B60D403C1.jpeg

E1F59729-2DCE-4CB0-83F7-7533D0ED8E96.jpeg

8062B08B-EA3C-4C7C-B3F5-F22A4322D06B.jpeg

471C66B5-8512-4880-A92B-7BAA50605445.jpeg

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