Keihin PWK jetting on a 2002 CR250..??

DanCaughell331
Edited Date/Time 7/10/2015 11:27am
Dearest users of Vital MX forums, I have some questions about jetting a pwk for the later style case reed CR's.

So it turns out my old man has a spare 39mm keihin he has laying around that's in good shape that he's going to let me borrow for awhile while I'm in town visiting next weekend. Currently I have the garbage mikuni TMX from the factory and as you all know jetting those is about as simple as Chinese math. I'm trying to get a good baseline for my jetting to start playing with, here are all the factors I can think of that would be of any use to anybody that might be able to help me. Comment if you need any other specs besides what I've come up with.

BIKE SETTINGS
•2002 cr 250
•boyesen Rad Valve
•pro circuit works pipe and 304 silencer
•pro circuit exhaust flange
•UNI filter
•05+ base gasket
•wiseco pro lite piston W/new cylinder
•stock porting & head/dome
•13/48 gearing
•sea level from 60-80* F (Oregon dunes)
•100 octane Sunoco fuel
•32:1 mixed with Castor 927

KEIHIN SPECS
•pwk 39mm (72RA4 SDJ)
•#6 slide
•DEJ needle (I think)
•long body carb

Currently it has a 150 main and 55 pilot, the main sounds a little on the lean side? It will be ridden on sand and since I'll be twisting on it I don't want to run it lean and burn down my brand new powerplant. But then again mikuni and keihin jet numbers are leaps and bounds different. Any help would be greatly appreciated!!







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scooter5002
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scooter5002 7/8/2015 5:08pm
7/8/2015 5:08pm
Purely a guess on my part, but I'd think at least a 170/172 main to start. CamP has got a couple of threads here about a build on his late model CR250, search for those, he has put a lot of info into those. He's also replied to other guys on their questions, so do some digging through his posts. You'll find something.
CrGuy2T
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CrGuy2T 7/8/2015 5:41pm
7/8/2015 5:41pm
I can't remember exactly what I had in mine but I'd jetting sent me his kit for my pwk and it was very close I just had to move the needle one clip down.
digger
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digger 7/8/2015 8:38pm
7/8/2015 8:38pm
I have a ton of time in jetting those PWK equipped cr 125's and 250's. You've got a 91mm in length PWK, which will fit perfect into you bike. Unfortunately you didn't take a pic of the air box side of the carb, so I can't tell if it's and air striker or not. The jetting that is in it now looks confused. That DEJ needle would be used in a 125, but the 55 pilot is huge, while the 150 main is dangerously lean for sea level, on either a 125 or 250. The #6 slide would also work best in a 125, as it's rich for a 250.

I'll give you a couple of jetting combo's that will get you close , but that #6 slide is going to be a little rich. A #7 or #8 slide would be a much better option.

For mx I would use a Yamaha /KTM duel taper N3EJ in the #3 slot,with a 45 pilot, and a 178 main jet. I would start off with the air screw 2 turns out. This combo with the #6 slide will give you good torque on the bottom end, with nice hit into the mid range and good topend.

If you are looking for a smoother type of power through out. I would start out with a Suzuki triple taper NEDW needle in the #3 slot, with a 42 pilot. You may be able to get away a 40 pilot due to the slide, but let the air screw determine that. More that 2.5 turns out on the air screw and you will need the smaller pilot. I would also start out with a 172 main jet. This setup will a little less torque on the bottom end than the N3EJ, but a smoother transition into the mid and top, but still has decent over rev.

These combos are just to get you in the ball park, but should be pretty close.
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DanCaughell331 7/8/2015 9:18pm
7/8/2015 9:18pm
digger wrote:
I have a ton of time in jetting those PWK equipped cr 125's and 250's. You've got a 91mm in length PWK, which will fit perfect...
I have a ton of time in jetting those PWK equipped cr 125's and 250's. You've got a 91mm in length PWK, which will fit perfect into you bike. Unfortunately you didn't take a pic of the air box side of the carb, so I can't tell if it's and air striker or not. The jetting that is in it now looks confused. That DEJ needle would be used in a 125, but the 55 pilot is huge, while the 150 main is dangerously lean for sea level, on either a 125 or 250. The #6 slide would also work best in a 125, as it's rich for a 250.

I'll give you a couple of jetting combo's that will get you close , but that #6 slide is going to be a little rich. A #7 or #8 slide would be a much better option.

For mx I would use a Yamaha /KTM duel taper N3EJ in the #3 slot,with a 45 pilot, and a 178 main jet. I would start off with the air screw 2 turns out. This combo with the #6 slide will give you good torque on the bottom end, with nice hit into the mid range and good topend.

If you are looking for a smoother type of power through out. I would start out with a Suzuki triple taper NEDW needle in the #3 slot, with a 42 pilot. You may be able to get away a 40 pilot due to the slide, but let the air screw determine that. More that 2.5 turns out on the air screw and you will need the smaller pilot. I would also start out with a 172 main jet. This setup will a little less torque on the bottom end than the N3EJ, but a smoother transition into the mid and top, but still has decent over rev.

These combos are just to get you in the ball park, but should be pretty close.
Hey digger thanks for taking the time to throw some input in, I really appreciate it. As far as the needle that's in it, I'm not 100% EXACTLY sure if it is or not. My dad and I were talking on the phone and he had just mentioned the carb because I've been talking about a keihin swap for awhile now, and he's had it sitting in a box for some time as a spare for his bikes. He ball parked the needle but says he's pretty sure it's a DEJ. And the jetting was leaned out for whatever application it was used for when he bought the carb from the previous owner. Also, it is not an airstriker unfortunately. BUT with that being said, it should be a good amount better than the factory TMX on the bike right now.

As stated in your first scenario for jetting (178 main, 45 pilot) is that possible to use while using the DEJ, if in fact it is a DEJ, and #6 slide? Or would it change those sizes a lot between the N3EJ needle? I'm not opposed to swapping needles, I'm just not quite interested in swapping the slide just yet since it will only be ran for a couple weeks while I'm back in Oregon at sea level. Unfortunately I have a whole other set of jetting settings when I get back to Salt Lake City at 4500 ft. Lol

In all reality I'm not going for factory bike jetting status with a perfect chalky look in the silencer, but I do want to clean it up and get some better power out of it. It can be a little darker, I just don't want it to be wet and puking all over itself. Unfortunately since I do 95% of my riding in utah, it's hard to pinpoint on a guaranteed setting since the elevation changes so much out here. But getting it close at sea level with what is in it right now (minus a possible needle change and different jets) is what I'm trying to get at. Also, if you could elaborate on the different slide numbers and why a 6 would run richer than say, a 7 or 8? I know it has to do with the cut out of the bottom of the slide, but past that I don't know much else. Once again, thanks for all the info!

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digger
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digger 7/9/2015 7:00am
7/9/2015 7:00am
DanCaughell331 wrote:
Hey digger thanks for taking the time to throw some input in, I really appreciate it. As far as the needle that's in it, I'm not...
Hey digger thanks for taking the time to throw some input in, I really appreciate it. As far as the needle that's in it, I'm not 100% EXACTLY sure if it is or not. My dad and I were talking on the phone and he had just mentioned the carb because I've been talking about a keihin swap for awhile now, and he's had it sitting in a box for some time as a spare for his bikes. He ball parked the needle but says he's pretty sure it's a DEJ. And the jetting was leaned out for whatever application it was used for when he bought the carb from the previous owner. Also, it is not an airstriker unfortunately. BUT with that being said, it should be a good amount better than the factory TMX on the bike right now.

As stated in your first scenario for jetting (178 main, 45 pilot) is that possible to use while using the DEJ, if in fact it is a DEJ, and #6 slide? Or would it change those sizes a lot between the N3EJ needle? I'm not opposed to swapping needles, I'm just not quite interested in swapping the slide just yet since it will only be ran for a couple weeks while I'm back in Oregon at sea level. Unfortunately I have a whole other set of jetting settings when I get back to Salt Lake City at 4500 ft. Lol

In all reality I'm not going for factory bike jetting status with a perfect chalky look in the silencer, but I do want to clean it up and get some better power out of it. It can be a little darker, I just don't want it to be wet and puking all over itself. Unfortunately since I do 95% of my riding in utah, it's hard to pinpoint on a guaranteed setting since the elevation changes so much out here. But getting it close at sea level with what is in it right now (minus a possible needle change and different jets) is what I'm trying to get at. Also, if you could elaborate on the different slide numbers and why a 6 would run richer than say, a 7 or 8? I know it has to do with the cut out of the bottom of the slide, but past that I don't know much else. Once again, thanks for all the info!
For that particular needle(DEJ) I think a 45 and 178 will work, it may even need a 48 pilot, but either way it is going to be rich, because of the 1.45 taper of that needle. Because the carb is a 39mm non AS carb, it may need 1 main jet size larger than a std 38mm AS carb.

The difference between the slides, 6 & 7, is that a #7 slide is 1mm taller & wider through the arch on the intake side of the slide than the #6. The #8 is another 1mm larger than the #7 etc.. The slide has an affect on the jetting of the carb up to about 40% of the throttle range.

I have worked with people on jetting these Hondas at elevation, The jetting doesn't that radically. At 4500' you are going to go down about 2 sizes on the main, the air screw may need to be adjusted out leaner. With the needle being the same at sea level and elevation. It may need to be moved 1 clip position leaner. At really high elevation you would actually need the richer slide.

I think you be suprised at how clean the bike will run when it's jetted correctly when compared to the Mikuni TMX carb. We are not talking about a huge investment here either. The largest being the slide, but that can be cut to a #7 for about $20. The needle jets are pretty cheap.
http://www.partzilla.com/parts/detail/yamaha/YP-4SR-14916-EJ-00.html
http://www.partzilla.com/parts/detail/suzuki/SP-13383-37FL0.html
https://www.jdjetting.com/xcart/product.php?productid=100&cat=17&page=1
http://rb-designs.com/rb_designs_llc_013.htm
captmoto
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captmoto 7/9/2015 11:36am
7/9/2015 11:36am
Need a #7 slide for sure. I run 175/178 main, 45/48 slow jet and 1368 needle on the middle slot. The 1368 is the same as the CEJ needle. I can't remember exactly and I didn't write mine down but that should get you very close. I have that same carb sitting and would part with it for $150, very low time. I changed it out for a late model YZ carb and am going to use the TP sensor. You may have to push a little on the air boot to get it to fit but jetting changes is way easier with the screw top.
http://www.suzukipartshouse.com/oemparts/p/honda/16202-ml3-681/needle-s…
DanCaughell331 7/9/2015 12:09pm
7/9/2015 12:09pm
digger wrote:
For that particular needle(DEJ) I think a 45 and 178 will work, it may even need a 48 pilot, but either way it is going to...
For that particular needle(DEJ) I think a 45 and 178 will work, it may even need a 48 pilot, but either way it is going to be rich, because of the 1.45 taper of that needle. Because the carb is a 39mm non AS carb, it may need 1 main jet size larger than a std 38mm AS carb.

The difference between the slides, 6 & 7, is that a #7 slide is 1mm taller & wider through the arch on the intake side of the slide than the #6. The #8 is another 1mm larger than the #7 etc.. The slide has an affect on the jetting of the carb up to about 40% of the throttle range.

I have worked with people on jetting these Hondas at elevation, The jetting doesn't that radically. At 4500' you are going to go down about 2 sizes on the main, the air screw may need to be adjusted out leaner. With the needle being the same at sea level and elevation. It may need to be moved 1 clip position leaner. At really high elevation you would actually need the richer slide.

I think you be suprised at how clean the bike will run when it's jetted correctly when compared to the Mikuni TMX carb. We are not talking about a huge investment here either. The largest being the slide, but that can be cut to a #7 for about $20. The needle jets are pretty cheap.
http://www.partzilla.com/parts/detail/yamaha/YP-4SR-14916-EJ-00.html
http://www.partzilla.com/parts/detail/suzuki/SP-13383-37FL0.html
https://www.jdjetting.com/xcart/product.php?productid=100&cat=17&page=1
http://rb-designs.com/rb_designs_llc_013.htm
Thanks again for taking the time to school a new buck on these carbs! Well since it's my fathers carb I probably won't have the slide cut just in case he has other plans for it later once I head back to utah and snag my own pwk up. I like the sounds of the MX set up with the N3EJ needle, because I like the harder two stroke hit especially in sand where it needs the power anyways. From the sounds of it mid-high 170's on the main and a mid 40's pilot seems to be common in these setups. I'll call some shops back home and see if they have the needle so I can snag one up when I get there or know to order it so I have it on hand right off the bat. And jets are already covered for all sizes on main and pilot.

So you think with the #6 slide, N3EJ needle and 175-178 main should run pretty solid in comparison to the Mikuni?
DanCaughell331 7/9/2015 12:14pm
7/9/2015 12:14pm
captmoto wrote:
Need a #7 slide for sure. I run 175/178 main, 45/48 slow jet and 1368 needle on the middle slot. The 1368 is the same as...
Need a #7 slide for sure. I run 175/178 main, 45/48 slow jet and 1368 needle on the middle slot. The 1368 is the same as the CEJ needle. I can't remember exactly and I didn't write mine down but that should get you very close. I have that same carb sitting and would part with it for $150, very low time. I changed it out for a late model YZ carb and am going to use the TP sensor. You may have to push a little on the air boot to get it to fit but jetting changes is way easier with the screw top.
http://www.suzukipartshouse.com/oemparts/p/honda/16202-ml3-681/needle-s…
Thanks for the info on jetting these things, makes my life a whole lot easier! What carb are you willing to sell? 38 or 39? And is it an A/S or just a standard PWK? Because I am in the market for a Keihin to finally finish out the motor package.
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Bruce372 7/9/2015 12:44pm
7/9/2015 12:44pm
The spigot tapers out a little, so its probably a 38mm

If anyone needs a #4 slide for these carbs, I have one for sale. It can easily be cut leaner with a file
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digger 7/9/2015 4:01pm
7/9/2015 4:01pm
captmoto wrote:
Need a #7 slide for sure. I run 175/178 main, 45/48 slow jet and 1368 needle on the middle slot. The 1368 is the same as...
Need a #7 slide for sure. I run 175/178 main, 45/48 slow jet and 1368 needle on the middle slot. The 1368 is the same as the CEJ needle. I can't remember exactly and I didn't write mine down but that should get you very close. I have that same carb sitting and would part with it for $150, very low time. I changed it out for a late model YZ carb and am going to use the TP sensor. You may have to push a little on the air boot to get it to fit but jetting changes is way easier with the screw top.
http://www.suzukipartshouse.com/oemparts/p/honda/16202-ml3-681/needle-s…
The 1368n needle is NOT the same as a CEJ. The 1368n is 2 clip postions leaner than a CEJ eg: The 1368n in the #3 clip is equal to CEJ in the 1 clip. The 1368n needle is the same as a CGJ needle.
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digger 7/9/2015 4:09pm
7/9/2015 4:09pm
DanCaughell331 wrote:
Thanks again for taking the time to school a new buck on these carbs! Well since it's my fathers carb I probably won't have the slide...
Thanks again for taking the time to school a new buck on these carbs! Well since it's my fathers carb I probably won't have the slide cut just in case he has other plans for it later once I head back to utah and snag my own pwk up. I like the sounds of the MX set up with the N3EJ needle, because I like the harder two stroke hit especially in sand where it needs the power anyways. From the sounds of it mid-high 170's on the main and a mid 40's pilot seems to be common in these setups. I'll call some shops back home and see if they have the needle so I can snag one up when I get there or know to order it so I have it on hand right off the bat. And jets are already covered for all sizes on main and pilot.

So you think with the #6 slide, N3EJ needle and 175-178 main should run pretty solid in comparison to the Mikuni?
The needle jet is the heart of the carburetor, it determines what pilot and main will need to be used.

The #6 slide, N3EJ, 45 pilot and 178 main to start with will be a solid combo. It will just run a little rougher down low, and have a little more hit, than if you were using a #7 slide. Start off with the 178 main you may very well be able to use the 175, but I would rather you start off a touch rich on the main and work your way down if need be.
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captmoto 7/10/2015 10:27am
7/10/2015 10:27am
DanCaughell331 wrote:
Thanks for the info on jetting these things, makes my life a whole lot easier! What carb are you willing to sell? 38 or 39? And...
Thanks for the info on jetting these things, makes my life a whole lot easier! What carb are you willing to sell? 38 or 39? And is it an A/S or just a standard PWK? Because I am in the market for a Keihin to finally finish out the motor package.
It's this carb from CPW.
http://www.carbparts.com/index.html
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captmoto 7/10/2015 10:31am
7/10/2015 10:31am
digger wrote:
The 1368n needle is NOT the same as a CEJ. The 1368n is 2 clip postions leaner than a CEJ eg: The 1368n in the #3...
The 1368n needle is NOT the same as a CEJ. The 1368n is 2 clip postions leaner than a CEJ eg: The 1368n in the #3 clip is equal to CEJ in the 1 clip. The 1368n needle is the same as a CGJ needle.
Not sure if the "N" designation is different from "NS". I went that way after reading all CamPs post on here and Thumpertalk where there was 20+ pages of discussion. Maybe I goofed but my bike runs really well.
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digger 7/10/2015 11:27am
7/10/2015 11:27am
captmoto wrote:
Not sure if the "N" designation is different from "NS". I went that way after reading all CamPs post on here and Thumpertalk where there was...
Not sure if the "N" designation is different from "NS". I went that way after reading all CamPs post on here and Thumpertalk where there was 20+ pages of discussion. Maybe I goofed but my bike runs really well.
I'm thinking it's a 1368 MS, which it an OEM needle from a mid to late 90's cr250, ,which is the same as a single taper CEJ needle. The only thing that really matters is that you are happy with it. I go by RTV over on the Thumpertalk board. You may have seen some of my post over there about jetting.
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Keith72 11/3/2016 4:38pm
11/3/2016 4:38pm Edited Date/Time 11/3/2016 4:40pm
digger, what can you tell me about an R1369MS needle? I am currently using the JD blue needle 2nd clip 172 main 45 pilot #7 slide. Going to try the N3CW next. Mostly MX. 2003 CR250. VForce 3 reeds. RB designs head mod.

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