Full Tilt CR250 Build - MXA Two Stroke Hall of Fame

blackdiamond
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blackdiamond 7/19/2016 5:36pm
7/19/2016 5:36pm
digger wrote:
I have a ton of time invested in jetting these Honda case reed engines, and honestly there are a bunch of different jetting and pipe setups...
I have a ton of time invested in jetting these Honda case reed engines, and honestly there are a bunch of different jetting and pipe setups that feel, butt dyno, great at any given time, and you'll think it can't get better, but it can, if you know what type of power you are after. I can help from a jetting perspective. You may not see it on a dyno chart taken at wfo, but you can feel the power differences on the track.

I really like using a #8 slide in most of the setups I run, depending on track conditions. The #8 slide really wakes up the throttle response all the way through the rev range. The Suzuki triple taper NECH needle when used with the #8 slide adds a ton of throttle response over the JD and #7 slide combo along with every other jetting combo that I have tried with a #7 slide. For pure bottom end, I prefer to use the duel taper Yamaha/KTM N3xx and other variants of this series needles. I use an N3CW in the Honda 250's. This series needle allows you to use a larger pilot and main jet, with the larger pilot helping out in the torque feel on the lowend. The bike simply pulls better down low with this series needle , and when combined with the #8 slide it has a nice transition into the middle. It's not as responsive as the NECH, but it has better lowend. IF you are looking for midrange power ? a Suzuki triple taper N3WJ, this is a completely different needle series than the Duel taper Yam/KTM series needles, is your best bet. This needle needs to be used with a #7, or custom 7.5 slide. It was a little lean when I tested it with the #8 slide. I know one of the posts above was about using the Honda series, spec 715 needle, and honestly that series is on of my least favorite ones that I have tested.

I have used all of the above combos and many, many more using a few different pipe combos, OEM, FMF Gnarly and Fatty, along a PC pipe. The FMF fatty and PC pipes are now garage wall art. I'm really not a topend kind of guy, so I have been using the Gnarly a lot lately. I really like the amount of lowend that it provides over all of the other pipes that I have tried.

One of the main reasons I run the Keihin carb in the first place is it is more consistent than the Mikuni. It's definitely easier to make more peak HP with the OEM Mikuni but you are going to be re-jetting that carb constantly. The same applies to the needles IMO. On a certain day on a certain track with a certain spec one combo may have a slight edge over another but I have found the JD needles to be the most consistent and require the least amount of changes 9 out of 10 times. That why I run the carb and the needles I do, I love crisp jetting but I HATE re-jetting.
digger
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digger 7/19/2016 8:01pm
7/19/2016 8:01pm
blackdiamond wrote:
One of the main reasons I run the Keihin carb in the first place is it is more consistent than the Mikuni. It's definitely easier to...
One of the main reasons I run the Keihin carb in the first place is it is more consistent than the Mikuni. It's definitely easier to make more peak HP with the OEM Mikuni but you are going to be re-jetting that carb constantly. The same applies to the needles IMO. On a certain day on a certain track with a certain spec one combo may have a slight edge over another but I have found the JD needles to be the most consistent and require the least amount of changes 9 out of 10 times. That why I run the carb and the needles I do, I love crisp jetting but I HATE re-jetting.
Everything that I listed above is for a Keihin PWK. I have used the above needles from April to September without issue here on the east coast.Your weather varies way less than ours. For you, those spec's that I listed would be set it and forget type deal. JD's jets are really nothing crazy. He uses a triple taper W starting diameter(red) and a G starting diameter (blue), both needles use the exact same profile tapers.

Of course a 38 Mikuni TMXX is going to make more HP at full throttle over the equivalent 38mm PWK. The 38mm TMXX's that I have, measure out to over 40mm. Where as the Honda, Yamaha and Kawasaki 38mm PWK's all seem to measure out to between 37.70--37.85mm. The 2 late model Suzuki spec'd 38mm PWK carbs seem to measure out at 38.8.
H4L
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H4L 7/19/2016 9:58pm
7/19/2016 9:58pm
As already noted bike setting is a personal preference. For me personally since I ride primarily mx the Gnarly is the worst pipe tested for that application. It will kill the topend power & go flat up top in the revs since the expansion chamber is designed for low-mid power. If your riding woods or slow trails I can see where this pipe might be a better option.
blackdiamond
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blackdiamond 7/20/2016 10:01am
7/20/2016 10:01am
blackdiamond wrote:
One of the main reasons I run the Keihin carb in the first place is it is more consistent than the Mikuni. It's definitely easier to...
One of the main reasons I run the Keihin carb in the first place is it is more consistent than the Mikuni. It's definitely easier to make more peak HP with the OEM Mikuni but you are going to be re-jetting that carb constantly. The same applies to the needles IMO. On a certain day on a certain track with a certain spec one combo may have a slight edge over another but I have found the JD needles to be the most consistent and require the least amount of changes 9 out of 10 times. That why I run the carb and the needles I do, I love crisp jetting but I HATE re-jetting.
digger wrote:
Everything that I listed above is for a Keihin PWK. I have used the above needles from April to September without issue here on the east...
Everything that I listed above is for a Keihin PWK. I have used the above needles from April to September without issue here on the east coast.Your weather varies way less than ours. For you, those spec's that I listed would be set it and forget type deal. JD's jets are really nothing crazy. He uses a triple taper W starting diameter(red) and a G starting diameter (blue), both needles use the exact same profile tapers.

Of course a 38 Mikuni TMXX is going to make more HP at full throttle over the equivalent 38mm PWK. The 38mm TMXX's that I have, measure out to over 40mm. Where as the Honda, Yamaha and Kawasaki 38mm PWK's all seem to measure out to between 37.70--37.85mm. The 2 late model Suzuki spec'd 38mm PWK carbs seem to measure out at 38.8.
The PWK I am running is bored to 39.5mm

The Shop

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needforspeed78 7/20/2016 10:29am
7/20/2016 10:29am
I received today this CDI, installed the program to my laptop and yeah, it is not the most user friendly interface, so I have to get familiar with it.
blackdiamond I will send you PM about the maps.
blackdiamond
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blackdiamond 7/20/2016 1:57pm
7/20/2016 1:57pm
I would have to agree, the software is tedious to say the least.
cslacker
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cslacker 7/20/2016 2:19pm
7/20/2016 2:19pm
digger wrote:
Everything that I listed above is for a Keihin PWK. I have used the above needles from April to September without issue here on the east...
Everything that I listed above is for a Keihin PWK. I have used the above needles from April to September without issue here on the east coast.Your weather varies way less than ours. For you, those spec's that I listed would be set it and forget type deal. JD's jets are really nothing crazy. He uses a triple taper W starting diameter(red) and a G starting diameter (blue), both needles use the exact same profile tapers.

Of course a 38 Mikuni TMXX is going to make more HP at full throttle over the equivalent 38mm PWK. The 38mm TMXX's that I have, measure out to over 40mm. Where as the Honda, Yamaha and Kawasaki 38mm PWK's all seem to measure out to between 37.70--37.85mm. The 2 late model Suzuki spec'd 38mm PWK carbs seem to measure out at 38.8.
What's strange to me is that everyone recommends a 45 or 48 pilot with the JD red needle with the 7 slide but yet with the NEDW needle people say 42. I actually tried the 42 NEDW 3rd clip and 172 main that most recommend as a starting point. It was definitely lean on the pilot and rich on the middle and main. Dropping the needle 1 clip helped lean the middle but it was too muddy to pull my float and change pilots so I just ended up at 1/2 turn out on airscrew to compensate for the lean pilot. I ended the day at NEDW 2nd clip and 168 main. I did my own measuring at home and came to the same conclusion as you that the red and NEDW have the same straight section diameter. I sent JD an email asking about the similarities and got no response. The red needle has a fatter tip than the NEDW for sure though.
Energyrail 7/20/2016 3:14pm
7/20/2016 3:14pm
Isn't there a hand held programer?
Or is it not worth using it vs. the computer.
digger
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digger 7/20/2016 4:07pm
7/20/2016 4:07pm
cslacker wrote:
What's strange to me is that everyone recommends a 45 or 48 pilot with the JD red needle with the 7 slide but yet with the...
What's strange to me is that everyone recommends a 45 or 48 pilot with the JD red needle with the 7 slide but yet with the NEDW needle people say 42. I actually tried the 42 NEDW 3rd clip and 172 main that most recommend as a starting point. It was definitely lean on the pilot and rich on the middle and main. Dropping the needle 1 clip helped lean the middle but it was too muddy to pull my float and change pilots so I just ended up at 1/2 turn out on airscrew to compensate for the lean pilot. I ended the day at NEDW 2nd clip and 168 main. I did my own measuring at home and came to the same conclusion as you that the red and NEDW have the same straight section diameter. I sent JD an email asking about the similarities and got no response. The red needle has a fatter tip than the NEDW for sure though.
The Suzuki NExx needles have a richer(thinner) end taper than the JD needles, which requires less fuel thru the main jet than the leaner(thicker) end taper of the JD needles. There is overlap between the needle and main jet circuits.

I've never come run a situation where I thought the 42 pilot was lean during the summer months in a case reed cr. The NEDW may very well be a little rich in the #3 clip. Have you tried the leaner NECW in the #3 ? A 1/2 clip position change can make quite a difference. I know that you very well can safely run a 168 main during the summer, but I like to throw in a little safety factor when recommending a main jet. Most people don't realize it, but all of JD's needles for 250cc 2t bikes are all the exact same needles. Your getting the exact same 2 needles, weather you have Yamaha, Suzuki, Kaw, GasGas etc....all the exact same W and G diameter needles.

blackdiamond
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blackdiamond 7/20/2016 4:16pm
7/20/2016 4:16pm
Energyrail wrote:
Isn't there a hand held programer?
Or is it not worth using it vs. the computer.
There is but I prefer the laptop. There are up to 12 points on the curve to program at 3 different throttle positions so that is 36 data points not including the PV map. That's a lot of data entry for a handheld device.
blackdiamond
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blackdiamond 7/22/2016 12:47pm
7/22/2016 12:47pm
needforspeed78 wrote:
I received today this CDI, installed the program to my laptop and yeah, it is not the most user friendly interface, so I have to get...
I received today this CDI, installed the program to my laptop and yeah, it is not the most user friendly interface, so I have to get familiar with it.
blackdiamond I will send you PM about the maps.
When you bought the Zeel CDI did they give you any base maps to start with?
Travis_Hudson 7/23/2016 10:13am
7/23/2016 10:13am
That's funny, I went to a 178 on the main with my motor, 175 felt to lean.
gsxr6
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gsxr6 7/23/2016 10:23am
7/23/2016 10:23am Edited Date/Time 7/23/2016 10:25am
I prefer a 52 and 180 in my pwk( non airstryker) on my 02 cr. It's been Mildley ported, and I do weigh 220 without gear, so perhaps it likes more fuel. The 178 pinged in the top end, and even a 48 pilot made the roll on feel weak. I do run 32:1 and blendz all, so bigger jets than u 40:1 guys is to be expected. That being said I love the way it runs, even with the gnarly the top end seems to just pull forever almost like a 250f. Only much faster haha. Also I use garbage 91 pump gas.
needforspeed78 7/23/2016 11:09am
7/23/2016 11:09am
blackdiamond wrote:
When you bought the Zeel CDI did they give you any base maps to start with?
I havent plugged my CDI yet to my bike so I dont know what kind of map there is at the moment inside. There were no tune files included at CD where the tune program was, just got one A4 paper, where is one suggested ignition map and 6 PV maps..
blackdiamond
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blackdiamond 7/23/2016 2:51pm
7/23/2016 2:51pm
Travis_Hudson wrote:
That's funny, I went to a 178 on the main with my motor, 175 felt to lean.
What fuel were you running? The fuel and compression have a big affect on that as well.
blackdiamond
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blackdiamond 7/23/2016 2:58pm
7/23/2016 2:58pm
needforspeed78 wrote:
I havent plugged my CDI yet to my bike so I dont know what kind of map there is at the moment inside. There were no...
I havent plugged my CDI yet to my bike so I dont know what kind of map there is at the moment inside. There were no tune files included at CD where the tune program was, just got one A4 paper, where is one suggested ignition map and 6 PV maps..
I didn't have much luck with any of the six maps they gave me for the PV
gsxr6
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gsxr6 7/23/2016 3:05pm
7/23/2016 3:05pm Edited Date/Time 7/23/2016 3:06pm
Awesome article in mxa btw. Called the suspension perfect, said the power was way hooked up and fast, if the front end was down haha. Even mentioned big name riders getting passed up the hill. They seemed really impressed probably the most positive review I remember. Def my favorite bike build to be found.
blackdiamond
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blackdiamond 7/23/2016 5:32pm
7/23/2016 5:32pm
I thought it was one of the most detailed, comprehensive bike tests I have seen in MXA in a long time (I am not just saying this because it was my machine)

Pit Row

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CamP
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CamP 7/24/2016 6:11pm
7/24/2016 6:11pm Edited Date/Time 7/24/2016 6:23pm
blackdiamond wrote:
I thought it was one of the most detailed, comprehensive bike tests I have seen in MXA in a long time (I am not just saying...
I thought it was one of the most detailed, comprehensive bike tests I have seen in MXA in a long time (I am not just saying this because it was my machine)
Have you experimented with the straight taper Sudco needles? I'm running a .030" base cut cylinder on my 05 and 07 CR250's, with the stock head and VP110. Cranking pressure is 250psi. I've had great summer results with a CEJ needle at the middle clip, 175 main, a 48 pilot, and air screw at 1.75 turns out. Under 75f degrees, I simply raise the needle one clip position and it runs great down to the 40's. Bike is typically used for mx only at 600', but I just got back from a trip to CO where we rode from 7-11K feet and the bike was a tractor with the CEJ needle at the 2nd clip, 168 main, a 45 pilot, and the air screw at 2.75 turns out. Got lucky with that jetting as it was just an educated guess.

BTW, I'm running 38mm YZ250 carbs with the TPS connected and the powerjet circuit plugged. Your results may vary with your bored carb and portwork.
1
Awesome Johnson 7/24/2016 9:38pm
7/24/2016 9:38pm
Awesome Johnson wrote:
Blackdiamondwhen you get that ignition all sorted out I'm sure there will be a few of us looking to buy your tune. Great job on the...
Blackdiamondwhen you get that ignition all sorted out I'm sure there will be a few of us looking to buy your tune. Great job on the bike man. Thing is pure badass right to the core. I wish you'd spill the beans on which pro 450 guys got spanked up mt st.helen. You know that blew their mind experiencing that!
blackdiamond wrote:
You and I both know if I post that I am basically jumping in front of the Vital firing squad and we all know that escalates...
You and I both know if I post that I am basically jumping in front of the Vital firing squad and we all know that escalates quickly... Laughing

It was an orange bike and it was a two digit number, that's all you are going to get out of me.
Very true and fair enoughWink
blackdiamond
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blackdiamond 7/24/2016 9:58pm
7/24/2016 9:58pm
CamP wrote:
Have you experimented with the straight taper Sudco needles? I'm running a .030" base cut cylinder on my 05 and 07 CR250's, with the stock head...
Have you experimented with the straight taper Sudco needles? I'm running a .030" base cut cylinder on my 05 and 07 CR250's, with the stock head and VP110. Cranking pressure is 250psi. I've had great summer results with a CEJ needle at the middle clip, 175 main, a 48 pilot, and air screw at 1.75 turns out. Under 75f degrees, I simply raise the needle one clip position and it runs great down to the 40's. Bike is typically used for mx only at 600', but I just got back from a trip to CO where we rode from 7-11K feet and the bike was a tractor with the CEJ needle at the 2nd clip, 168 main, a 45 pilot, and the air screw at 2.75 turns out. Got lucky with that jetting as it was just an educated guess.

BTW, I'm running 38mm YZ250 carbs with the TPS connected and the powerjet circuit plugged. Your results may vary with your bored carb and portwork.
I have not tried one mainly because I have always liked the feel of the JD red needles. Wow, that is a ton of cranking pressure!

Where did you ride in Colorado? I lived there for 15 years before moving to CA, there are so many amazing multi use trails there.
needforspeed78 7/25/2016 3:20am
7/25/2016 3:20am
blackdiamond, where did you mount the CDI box in your bike? I noticed that there is not enough space for it behind the number plate
CamP
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CamP 7/25/2016 5:38am
7/25/2016 5:38am Edited Date/Time 7/25/2016 5:41am
blackdiamond wrote:
I have not tried one mainly because I have always liked the feel of the JD red needles. Wow, that is a ton of cranking pressure...
I have not tried one mainly because I have always liked the feel of the JD red needles. Wow, that is a ton of cranking pressure!

Where did you ride in Colorado? I lived there for 15 years before moving to CA, there are so many amazing multi use trails there.
I have some friends that live in Pagosa Springs and they took me up into the Rio Grande National Forest, northwest of town. Then we rode in the San Juan National forest, northwest of Durango. It was some of the gnarliest single track I've ever seen. I'm not a trail rider type, but it was epic. I was really lucky to have skilled locals showing me their favorite trails.
blackdiamond
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blackdiamond 7/25/2016 9:29am
7/25/2016 9:29am
needforspeed78 wrote:
blackdiamond, where did you mount the CDI box in your bike? I noticed that there is not enough space for it behind the number plate
The only reasonable location for it is at the very rear of the air box because of its size. I fabricated a removable tray that pops in and out allowing easier servicing of the air filter. I'm out of town for work for a week but when I return I can post some pics. It's tricky, I tried mounting it in the middle of the bike earlier in the build but it's just too complicated to do correctly in that area. The cleanest, coolest and most waterproof area is in the air box.
JW381
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JW381 7/25/2016 12:33pm
7/25/2016 12:33pm
Travis_Hudson wrote:
That's funny, I went to a 178 on the main with my motor, 175 felt to lean.
blackdiamond wrote:
What fuel were you running? The fuel and compression have a big affect on that as well.
Can you elaborate a little? I'm running a 172 (170 when the Temps go above 85) 42 and a JD red needle on the 2nd from the top. Very lean compared to other settings. I'm running a blend of 97 and 110 with Super M at 40:1. 04 with a 00 CR PWK. I suspect I have weak spark or not enough air flow.
blackdiamond
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blackdiamond 7/25/2016 9:55pm
7/25/2016 9:55pm
CamP wrote:
I have some friends that live in Pagosa Springs and they took me up into the Rio Grande National Forest, northwest of town. Then we rode...
I have some friends that live in Pagosa Springs and they took me up into the Rio Grande National Forest, northwest of town. Then we rode in the San Juan National forest, northwest of Durango. It was some of the gnarliest single track I've ever seen. I'm not a trail rider type, but it was epic. I was really lucky to have skilled locals showing me their favorite trails.
The locals are the key in Colorado for sure. There is another whole world that the average riders don't even know about and the same is true with MTB rides. Some amazing terrain back there.
blackdiamond
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blackdiamond 7/26/2016 1:29am
7/26/2016 1:29am
Travis_Hudson wrote:
That's funny, I went to a 178 on the main with my motor, 175 felt to lean.
blackdiamond wrote:
What fuel were you running? The fuel and compression have a big affect on that as well.
JW381 wrote:
Can you elaborate a little? I'm running a 172 (170 when the Temps go above 85) 42 and a JD red needle on the 2nd from...
Can you elaborate a little? I'm running a 172 (170 when the Temps go above 85) 42 and a JD red needle on the 2nd from the top. Very lean compared to other settings. I'm running a blend of 97 and 110 with Super M at 40:1. 04 with a 00 CR PWK. I suspect I have weak spark or not enough air flow.
Is the bike having a specific problem of some sort?
CamP
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CamP 7/26/2016 4:33am
7/26/2016 4:33am
blackdiamond wrote:
The locals are the key in Colorado for sure. There is another whole world that the average riders don't even know about and the same is...
The locals are the key in Colorado for sure. There is another whole world that the average riders don't even know about and the same is true with MTB rides. Some amazing terrain back there.
Absolutely, the terrain was incredible and provided some real pucker factor in several sections. Very exposed areas where if you messed up, you'd be lucky if you walked away. Definitely provided some adrenaline rush.

Had the same experience on MTB's up in Bozeman, MT when some locals pointed us to their favorite local rides.
Michael_Brown 7/26/2016 5:20am
7/26/2016 5:20am
needforspeed78 wrote:
blackdiamond, where did you mount the CDI box in your bike? I noticed that there is not enough space for it behind the number plate
blackdiamond wrote:
The only reasonable location for it is at the very rear of the air box because of its size. I fabricated a removable tray that pops...
The only reasonable location for it is at the very rear of the air box because of its size. I fabricated a removable tray that pops in and out allowing easier servicing of the air filter. I'm out of town for work for a week but when I return I can post some pics. It's tricky, I tried mounting it in the middle of the bike earlier in the build but it's just too complicated to do correctly in that area. The cleanest, coolest and most waterproof area is in the air box.
Yeah I was trying to mount the cdi in the middle of the bike since I'm putting the 2015 forks on the front with the stabilizer like u did. And how hard was it make the coil bracket mount.
JW381
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JW381 7/26/2016 5:20am
7/26/2016 5:20am
blackdiamond wrote:
What fuel were you running? The fuel and compression have a big affect on that as well.
JW381 wrote:
Can you elaborate a little? I'm running a 172 (170 when the Temps go above 85) 42 and a JD red needle on the 2nd from...
Can you elaborate a little? I'm running a 172 (170 when the Temps go above 85) 42 and a JD red needle on the 2nd from the top. Very lean compared to other settings. I'm running a blend of 97 and 110 with Super M at 40:1. 04 with a 00 CR PWK. I suspect I have weak spark or not enough air flow.
blackdiamond wrote:
Is the bike having a specific problem of some sort?
Well I'm only at about 600'-800' elevation, wondering what is causing my bike to need such lean settings. It won't pull without the 170 main above 85 degrees. The 110 race fuel is made by renegade, and the 97 is just a higher octane non-ethanol premium. I'm not sure if the 110 is oxygenated. There is a hesitation in the middle, whenever I try the middle clip position it barely runs from being so rich. But I have not tried with the 170/42 combo yet. So when I see guys at similar elevation talking about 48P and 178M, I scratch my head a little. My plugs never indicate lean. They do, however, get uneven coloration. On half of the plug is coffee brown, the other is black.

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