Full Tilt CR250 Build - MXA Two Stroke Hall of Fame

H4L
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H4L 7/16/2016 9:28pm
7/16/2016 9:28pm
blackdiamond wrote:
Honestly, the one thing I am 110% satisfied with on the engine is the jetting. It's as perfect as it needs to be and I am...
Honestly, the one thing I am 110% satisfied with on the engine is the jetting. It's as perfect as it needs to be and I am not sure how it could be improved much if any. It starts in 1 or 2 kicks (without a choke) and is almost flawless on the track. I have a few other things I want to test and try to improve on with the ignition mapping and a 10oz flywheel weight but I am totally satisfied with the carb.

Other tuners I have talked to that have tested JD needles in the Mikuni absolutely raved about them but I am sure that is personal preference.
Agree. Bike set up can be a personal preference thing. Just curious on the tuners that liked the JD needles on the mikuni. Was it on the 01-03 longer body tmx or shorter body tps version 04-07 ?
blackdiamond
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blackdiamond 7/16/2016 10:25pm
7/16/2016 10:25pm
That was on a 2003 with the longer body
rocketsocks26 7/17/2016 6:18am
7/17/2016 6:18am
bd, beautiful build! curious are you following chad watts rc replica build on IG?
H4L
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H4L 7/17/2016 7:59am
7/17/2016 7:59am Edited Date/Time 7/17/2016 8:47am
blackdiamond wrote:
That was on a 2003 with the longer body
Thanks BD. Also tested with an 03 model. Interesting maybe the PC cyl. & head mods didn't work well the JD needles in my case.

Went back & looked at your spec sheet to see what gearing combo you're running. I've been running a 13/49-50 combo for many yrs. & was thinking of changing it up. Was thinking of trying a 14/50 & noticed your running a 14/51. How does your gear combo compare to a 13/50 ?

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blackdiamond
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blackdiamond 7/17/2016 2:28pm
7/17/2016 2:28pm
The 14/51 is a bit taller and I would definitely think with a built engine you would need taller gearing than the 13/50. I would start with the stock gearing (13/48) and go from there with testing but going lower is definitely the wrong way IMO.The bike will carry each gear longer and hook up better as well.
8686
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8686 7/17/2016 2:39pm
7/17/2016 2:39pm
blackdiamond wrote:
The 14/51 is a bit taller and I would definitely think with a built engine you would need taller gearing than the 13/50. I would start...
The 14/51 is a bit taller and I would definitely think with a built engine you would need taller gearing than the 13/50. I would start with the stock gearing (13/48) and go from there with testing but going lower is definitely the wrong way IMO.The bike will carry each gear longer and hook up better as well.
I agree on the gearing, especially if you have a few more hp to pull it. Either one up on the front or down a couple on the rear will mean less shifting and better traction. An adjustment that pairs well with adding flywheel weight. Slow down (the engine) to go faster.

A thought on the carb jetting. I always thought if the bike started with no choke when cold then the idle circuit was too rich. I felt the choke was there for a reason and designed to be that way. Of course this is only when completely cold.
H4L
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H4L 7/17/2016 3:57pm
7/17/2016 3:57pm
blackdiamond wrote:
The 14/51 is a bit taller and I would definitely think with a built engine you would need taller gearing than the 13/50. I would start...
The 14/51 is a bit taller and I would definitely think with a built engine you would need taller gearing than the 13/50. I would start with the stock gearing (13/48) and go from there with testing but going lower is definitely the wrong way IMO.The bike will carry each gear longer and hook up better as well.
Yeah. The 13/50 gearing with the PC mods provides a monstrous off idle low end pull & eats rear tires like it's going out of style. it also has a meaty mid range that goes into an healthy (insane) topend pull with added over-rev. Since the mods provide a wide powerful rpm range the engine doesn't run out of gear with the lower gear ratio (at local tracks). The engine actually likes to be ridden in the mid to upper part of the power band. Absolutely loved this combo for many years.
Now looking to detune it a bit since I'm no longer racing mx. Definitely wanting to get better traction with a higher gear ratio & possibly a heavier flywheel weight. After riding the 450 lately it got me thinking about getting better traction.
Thanks guys for your input.
blackdiamond
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blackdiamond 7/17/2016 4:36pm
7/17/2016 4:36pm
8686 wrote:
I agree on the gearing, especially if you have a few more hp to pull it. Either one up on the front or down a couple...
I agree on the gearing, especially if you have a few more hp to pull it. Either one up on the front or down a couple on the rear will mean less shifting and better traction. An adjustment that pairs well with adding flywheel weight. Slow down (the engine) to go faster.

A thought on the carb jetting. I always thought if the bike started with no choke when cold then the idle circuit was too rich. I felt the choke was there for a reason and designed to be that way. Of course this is only when completely cold.
In California it really doesn't matter because it never really gets cold (at least where I ride) Other parts of the country that would not be the case.
8686
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8686 7/17/2016 5:22pm
7/17/2016 5:22pm
blackdiamond wrote:
In California it really doesn't matter because it never really gets cold (at least where I ride) Other parts of the country that would not be...
In California it really doesn't matter because it never really gets cold (at least where I ride) Other parts of the country that would not be the case.
I only meant when the engine is cold, i.e. first time started each day.
blackdiamond
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blackdiamond 7/17/2016 6:28pm
7/17/2016 6:28pm
8686 wrote:
I only meant when the engine is cold, i.e. first time started each day.
Then it takes about 5 kicks.
blackdiamond
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blackdiamond 7/17/2016 9:45pm
7/17/2016 9:45pm
rocketsocks26 wrote:
bd, beautiful build! curious are you following chad watts rc replica build on IG?
Oh yea, of course I am! When anything is happening involving a red two stroke I am definitely paying attention Smile
1
Energyrail 7/17/2016 11:17pm
7/17/2016 11:17pm
Energyrail wrote:
Do you believe the suggested timing and powervalve maps given to you by zealtronic were exact replicas of the Honda? Or did you have to dyno...
Do you believe the suggested timing and powervalve maps given to you by zealtronic were exact replicas of the Honda? Or did you have to dyno to get it working as good as stock.
I want the ignition so I can have a map switch to tame the hit for trail riding.
I've already lowered the cyl .030".
H4L wrote:
Have you tried a heavier flywheel weight or a lower gear ratio ? Those two options will help reduce the hit & be more cost effective...
Have you tried a heavier flywheel weight or a lower gear ratio ? Those two options will help reduce the hit & be more cost effective.
An aftermarket ign. will be more complicated since you have to have the software to achieve a desirable map. It will also take time to fine tune it. That being said If you have the funds & the know how it can be a very good option.
I have a 10 ounce on it. I have 13 to try next.
Were the ignition maps any better?
Is anyone selling their maps they built to help pay for their dyno time.
blackdiamond
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blackdiamond 7/18/2016 12:38am
7/18/2016 12:38am
The ignition base maps I received were even worse than the PV maps. The biggest problem is that this ignition and PV controller have been largely used by the Kart and road racing community and there is very little information available for the MX arena. I did my own baseline map based on a ton of info gathered from several different data sources, tuners and theories and ended up with a 1.5 HP gain at peak over the OEM system. The biggest achievement on that day however was syncing the PV mapping with the pipe and eliminating any holes in the curve and creating an extremely linear and broad (almost 4 stroke like) curve.

I am going to be doing much more testing in a week or two and expect to find some more HP at that time. I would be willing to do custom mapping once I feel this package is as perfect as I feel it can be at a very reasonable price if anyone is interested.
needforspeed78 7/18/2016 2:38am
7/18/2016 2:38am
blackdiamond wrote:
The ignition base maps I received were even worse than the PV maps. The biggest problem is that this ignition and PV controller have been largely...
The ignition base maps I received were even worse than the PV maps. The biggest problem is that this ignition and PV controller have been largely used by the Kart and road racing community and there is very little information available for the MX arena. I did my own baseline map based on a ton of info gathered from several different data sources, tuners and theories and ended up with a 1.5 HP gain at peak over the OEM system. The biggest achievement on that day however was syncing the PV mapping with the pipe and eliminating any holes in the curve and creating an extremely linear and broad (almost 4 stroke like) curve.

I am going to be doing much more testing in a week or two and expect to find some more HP at that time. I would be willing to do custom mapping once I feel this package is as perfect as I feel it can be at a very reasonable price if anyone is interested.
Im interested, if price is reasonable. I just bought this CDI for my 06 CR250, that im building at the moment.
Helder
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Helder 7/18/2016 2:53am
7/18/2016 2:53am
BD what's the plan for the bike will you sell it or race it put it in your workshop?
cslacker
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cslacker 7/18/2016 7:42am
7/18/2016 7:42am
blackdiamond wrote:
What did you finally end up with for jetting specs? I am going to be doing some more dyno runs in a few weeks and I...
What did you finally end up with for jetting specs? I am going to be doing some more dyno runs in a few weeks and I might mess around with some different jetting combos while it's on the dyno to see how it affects the numbers..
I wish I had an update on mine but the 110 degree weather has thrown a wrench in any testing I have done. It will probably be another couple weeks before I am back to any type of schedule where testing will be possible. I absolutely hate summer in AZ...
blackdiamond
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blackdiamond 7/18/2016 1:05pm
7/18/2016 1:05pm
Helder wrote:
BD what's the plan for the bike will you sell it or race it put it in your workshop?
I am planning on riding the hell out of it in the near future. I cut my hand badly last weekend and its going to be a bit before I can moto and hang on.
blackdiamond
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blackdiamond 7/18/2016 1:49pm
7/18/2016 1:49pm
needforspeed78 wrote:
Im interested, if price is reasonable. I just bought this CDI for my 06 CR250, that im building at the moment.
Who is doing the porting? What pipe are you using?

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needforspeed78 7/18/2016 7:56pm
7/18/2016 7:56pm
needforspeed78 wrote:
Im interested, if price is reasonable. I just bought this CDI for my 06 CR250, that im building at the moment.
blackdiamond wrote:
Who is doing the porting? What pipe are you using?
Porting, head and carburetor is done by the local tuner, I have a OEM pipe and PC Platinum. At first I will propably use OEM pipe, as late model 05-07 pipe should perform good.
I will also use pump fuel, since I dont have access to race fuel near me.

Many people with 02-07 Honda´s seem to go with 0.30" lowered cyl. and are happy with the results. I will try first without cutting the base of the cylinder and if I will need more bottom end grunt I can always do it afterwards

BD, do you know has your cylinder been lowered from the original height? Are you controlling Powerjet with your CDI, or is it plugged off?


blackdiamond
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blackdiamond 7/18/2016 8:05pm
7/18/2016 8:05pm
needforspeed78 wrote:
Porting, head and carburetor is done by the local tuner, I have a OEM pipe and PC Platinum. At first I will propably use OEM pipe...
Porting, head and carburetor is done by the local tuner, I have a OEM pipe and PC Platinum. At first I will propably use OEM pipe, as late model 05-07 pipe should perform good.
I will also use pump fuel, since I dont have access to race fuel near me.

Many people with 02-07 Honda´s seem to go with 0.30" lowered cyl. and are happy with the results. I will try first without cutting the base of the cylinder and if I will need more bottom end grunt I can always do it afterwards

BD, do you know has your cylinder been lowered from the original height? Are you controlling Powerjet with your CDI, or is it plugged off?


The stock pipe runs really well, almost identical to the HGS pipe. Either of them offer a far better spread over an FMF or PC pipe on this bike. Using pump fuel is really tough on the CR though. Varner lowers the cylinder on all CR250 engine packages.
Awesome Johnson 7/18/2016 8:44pm
7/18/2016 8:44pm
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
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blackdiamond 7/18/2016 8:57pm
7/18/2016 8:57pm
needforspeed78 wrote:
Porting, head and carburetor is done by the local tuner, I have a OEM pipe and PC Platinum. At first I will propably use OEM pipe...
Porting, head and carburetor is done by the local tuner, I have a OEM pipe and PC Platinum. At first I will propably use OEM pipe, as late model 05-07 pipe should perform good.
I will also use pump fuel, since I dont have access to race fuel near me.

Many people with 02-07 Honda´s seem to go with 0.30" lowered cyl. and are happy with the results. I will try first without cutting the base of the cylinder and if I will need more bottom end grunt I can always do it afterwards

BD, do you know has your cylinder been lowered from the original height? Are you controlling Powerjet with your CDI, or is it plugged off?


blackdiamond wrote:
The stock pipe runs really well, almost identical to the HGS pipe. Either of them offer a far better spread over an FMF or PC pipe...
The stock pipe runs really well, almost identical to the HGS pipe. Either of them offer a far better spread over an FMF or PC pipe on this bike. Using pump fuel is really tough on the CR though. Varner lowers the cylinder on all CR250 engine packages.
I forgot to add that the power-jet is controlled by the CDI and is functional.
blackdiamond
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blackdiamond 7/18/2016 11:08pm
7/18/2016 11:08pm
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!
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.
cslacker
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cslacker 7/19/2016 7:57am
7/19/2016 7:57am Edited Date/Time 7/19/2016 8:38am
blackdiamond wrote:
The stock pipe runs really well, almost identical to the HGS pipe. Either of them offer a far better spread over an FMF or PC pipe...
The stock pipe runs really well, almost identical to the HGS pipe. Either of them offer a far better spread over an FMF or PC pipe on this bike. Using pump fuel is really tough on the CR though. Varner lowers the cylinder on all CR250 engine packages.
Varner actually mentioned to me he doesn't cut the base as much as people think. Said he took mine down only about .008 or something like that. That might be different on the 05-07 engines though. On another note, his port work is truly a thing of beauty.
Orange724
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Orange724 7/19/2016 8:16am
7/19/2016 8:16am
I took my cylinder to a local engine guy and he said he wouldn't recommend shaving anything off the bottom of the cylinder, he said what you want to do is fix the squish with the head. I did the squish test with the solder and he said it was almost double what it should be, which he said was normal with the cr, apparently all the manufactures are off a little. He shaved some material off the base of the head, then added volume back to the combustion chamber so it can run on pump gas. I can tell he removed a fair amount because I had to ream out the head stay bolts for them to line up. Haven't got to ride it yet but I got a lot of testing to do, put on the kehien as well so I'm starting from scratch. Btw it's an 06. Good thing this bike handles so well and looks good because the motor is an enigma haha
blackdiamond
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blackdiamond 7/19/2016 11:50am
7/19/2016 11:50am
cslacker wrote:
Varner actually mentioned to me he doesn't cut the base as much as people think. Said he took mine down only about .008 or something like...
Varner actually mentioned to me he doesn't cut the base as much as people think. Said he took mine down only about .008 or something like that. That might be different on the 05-07 engines though. On another note, his port work is truly a thing of beauty.
I am sure it varies from one engine package to the next depending on what the rider is looking to achieve.
blackdiamond
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blackdiamond 7/19/2016 11:57am
7/19/2016 11:57am
Orange724 wrote:
I took my cylinder to a local engine guy and he said he wouldn't recommend shaving anything off the bottom of the cylinder, he said what...
I took my cylinder to a local engine guy and he said he wouldn't recommend shaving anything off the bottom of the cylinder, he said what you want to do is fix the squish with the head. I did the squish test with the solder and he said it was almost double what it should be, which he said was normal with the cr, apparently all the manufactures are off a little. He shaved some material off the base of the head, then added volume back to the combustion chamber so it can run on pump gas. I can tell he removed a fair amount because I had to ream out the head stay bolts for them to line up. Haven't got to ride it yet but I got a lot of testing to do, put on the kehien as well so I'm starting from scratch. Btw it's an 06. Good thing this bike handles so well and looks good because the motor is an enigma haha
Lowering the cylinder does more than just tighten the squish, it allows for more dramatic changes to the port timing once the cylinder is ported.
digger
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digger 7/19/2016 2:43pm
7/19/2016 2:43pm
blackdiamond wrote:
Honestly, the one thing I am 110% satisfied with on the engine is the jetting. It's as perfect as it needs to be and I am...
Honestly, the one thing I am 110% satisfied with on the engine is the jetting. It's as perfect as it needs to be and I am not sure how it could be improved much if any. It starts in 1 or 2 kicks (without a choke) and is almost flawless on the track. I have a few other things I want to test and try to improve on with the ignition mapping and a 10oz flywheel weight but I am totally satisfied with the carb.

Other tuners I have talked to that have tested JD needles in the Mikuni absolutely raved about them but I am sure that is personal preference.
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.

1
JW381
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JW381 7/19/2016 2:48pm
7/19/2016 2:48pm
blackdiamond wrote:
Honestly, the one thing I am 110% satisfied with on the engine is the jetting. It's as perfect as it needs to be and I am...
Honestly, the one thing I am 110% satisfied with on the engine is the jetting. It's as perfect as it needs to be and I am not sure how it could be improved much if any. It starts in 1 or 2 kicks (without a choke) and is almost flawless on the track. I have a few other things I want to test and try to improve on with the ignition mapping and a 10oz flywheel weight but I am totally satisfied with the carb.

Other tuners I have talked to that have tested JD needles in the Mikuni absolutely raved about them but I am sure that is personal preference.
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.

Great stuff
Helder
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Helder 7/19/2016 4:52pm
7/19/2016 4:52pm
Helder wrote:
BD what's the plan for the bike will you sell it or race it put it in your workshop?
blackdiamond wrote:
I am planning on riding the hell out of it in the near future. I cut my hand badly last weekend and its going to be...
I am planning on riding the hell out of it in the near future. I cut my hand badly last weekend and its going to be a bit before I can moto and hang on.
Love it man!! Very very jealous

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