Full Tilt CR250 Build - MXA Two Stroke Hall of Fame

AS64
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AS64 5/22/2016 7:11pm
5/22/2016 7:11pm Edited Date/Time 5/22/2016 7:14pm
I have a built motor in my YZ250 and I decided to try out an 8oz heavier flywheel (GYTR +8.04oz over stock). I didn't notice ANY less snap, especially with a single ring piston. It just smoothed out the hit and made it more tractable. IMO it only made the bike better and I didn't experience any negatives. I don't know what's available for the CR250s, but if you can find a heavier replacement flywheel, it doesn't hurt to try.
Langhammx 5/22/2016 7:28pm
5/22/2016 7:28pm
blackdiamond wrote:
We have had to re-schedule a few times but the current plan is for MXA to track test it at Glen Helen on Thursday. What year...
We have had to re-schedule a few times but the current plan is for MXA to track test it at Glen Helen on Thursday. What year is the RM250?
'04

It'll be finished next week, then the MXA crew will get it dirty for the first time.
ledger
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ledger 5/22/2016 10:04pm
5/22/2016 10:04pm Edited Date/Time 5/22/2016 10:12pm
We have bd's CR250 (CR550), bvm111's KX250, langhammx's RM250, and AS64's YZ250. How about an MXA Throwback Shootout ? Cool but seriously, I do agree on the fww if you're looking for a bit more hook-up. Guess it depends on track and track conditions.
blackdiamond
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blackdiamond 5/22/2016 10:09pm
5/22/2016 10:09pm
RMRider1 wrote:
I'd say no to the flywheel weight IMHO....Seems like you will be riding MX not tight trails right? Those big long stretches at Pala with that...
I'd say no to the flywheel weight IMHO....Seems like you will be riding MX not tight trails right? Those big long stretches at Pala with that pig wide open, you will never see the benefits I believe. If she is held mostly wide open all the time the flywheel weight benefits are negated or never realized....possibly a hindrance to peek rpm as well...
On a two stroke, more crank inertia (added crank or flywheel weight) should theoretically increase over-rev not decrease it. It works the opposite of what many think.

The Shop

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blackdiamond
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blackdiamond 5/22/2016 10:13pm
5/22/2016 10:13pm
Travis_Hudson wrote:
Not if you put a 8oz on it. Did you know that every factory two stroke in the nationals had a fly wheel weight on it...
Not if you put a 8oz on it. Did you know that every factory two stroke in the nationals had a fly wheel weight on it? Every one.
That's a good point, I have heard that 8-10 oz was the magic number for many of the factory teams back in the day so I would have to agree. I guess the testing is not quite over...
chump6784
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chump6784 5/22/2016 10:23pm
5/22/2016 10:23pm
MXA seem to like a 9 ounce fly wheel weight on their 250 2 stroke builds
ledger
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ledger 5/22/2016 11:02pm
5/22/2016 11:02pm
Jody at MXA will want to add a tooth.
blackdiamond
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blackdiamond 5/23/2016 12:44am
5/23/2016 12:44am
ledger wrote:
Jody at MXA will want to add a tooth.
Trust me, on this bike you will definitely not want to "add a tooth"

Maybe on the counter-shaft sprocket?
1
blackdiamond
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blackdiamond 5/23/2016 1:14am
5/23/2016 1:14am
ledger wrote:
We have bd's CR250 (CR550), bvm111's KX250, langhammx's RM250, and AS64's YZ250. How about an MXA Throwback Shootout ? B) but seriously, I do agree on...
We have bd's CR250 (CR550), bvm111's KX250, langhammx's RM250, and AS64's YZ250. How about an MXA Throwback Shootout ? Cool but seriously, I do agree on the fww if you're looking for a bit more hook-up. Guess it depends on track and track conditions.
Let's do it, I'm down.
emifrancy 5/26/2016 3:38am
5/26/2016 3:38am
Please, do you nave sane suggestions about the Keihin carb setting? Needle..ecc?
Many thanks!!
emifrancy 5/26/2016 3:40am
5/26/2016 3:40am
Please, do you have some suggestions about the keihin carb?..needle type ..etc.. Many thanks!
blackdiamond
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blackdiamond 5/26/2016 4:23am
5/26/2016 4:23am
emifrancy wrote:
Please, do you nave sane suggestions about the Keihin carb setting? Needle..ecc?
Many thanks!!
What carb are you running?
bvm111
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bvm111 5/26/2016 6:33am
5/26/2016 6:33am Edited Date/Time 5/26/2016 6:34am
ledger wrote:
We have bd's CR250 (CR550), bvm111's KX250, langhammx's RM250, and AS64's YZ250. How about an MXA Throwback Shootout ? B) but seriously, I do agree on...
We have bd's CR250 (CR550), bvm111's KX250, langhammx's RM250, and AS64's YZ250. How about an MXA Throwback Shootout ? Cool but seriously, I do agree on the fww if you're looking for a bit more hook-up. Guess it depends on track and track conditions.
blackdiamond wrote:
Let's do it, I'm down.
Let me know i am down as well...when and where!!!

That would be a lot of fun just to get together and ride!
TailSoHard
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TailSoHard 5/26/2016 7:05am
5/26/2016 7:05am
Has anyone crashed it yet?! I'd be terrified that someone was going to dump it after all that work...
cslacker
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cslacker 5/26/2016 7:35am
5/26/2016 7:35am
Any issues with running the 2 right side RC Valve cables yet? Honda was claiming they had the spring on the left side to automatically take up slack but just looking at the setup it really doesn't do that. I bought 2 right side to give it a shot after looking at this.
blackdiamond
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blackdiamond 5/26/2016 9:33am
5/26/2016 9:33am
bvm111 wrote:
Let me know i am down as well...when and where!!!

That would be a lot of fun just to get together and ride!
I've got a tweaked ankle right now so it'll be up few weeks before I get back to the track anywhere. In fact I decided to pass on going to spectate the national because it would be too much of a chore to try to hike around all day with this injury the way it is right now. I will keep you posted though.
blackdiamond
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blackdiamond 5/26/2016 10:43am
5/26/2016 10:43am
TailSoHard wrote:
Has anyone crashed it yet?! I'd be terrified that someone was going to dump it after all that work...
Not yet, just a few smashed pipes and one smashed helmet.

Daryl Ecklund from MXA over-jumped one of the doubles by so much he smashed his helmet into the crossbar pad when we were at Glen Helen last week. He was ok, but the new Shoei got beat up a little bit.
blackdiamond
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blackdiamond 5/26/2016 10:58am
5/26/2016 10:58am
cslacker wrote:
Any issues with running the 2 right side RC Valve cables yet? Honda was claiming they had the spring on the left side to automatically take...
Any issues with running the 2 right side RC Valve cables yet? Honda was claiming they had the spring on the left side to automatically take up slack but just looking at the setup it really doesn't do that. I bought 2 right side to give it a shot after looking at this.
No, it's the way to go for sure. I am not sure what they were thinking with that stupid spring. I just looked at a few of the two stroke road race bikes and none of them have spring.

The picture below is what I ended up with for cable adjustment. The left is slammed all the way in, this is important in addition to the tension. Believe it or not, there is 3 HP hiding in the cable adjustment.



Pit Row

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cslacker
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cslacker 5/26/2016 11:07am
5/26/2016 11:07am
blackdiamond wrote:
No, it's the way to go for sure. I am not sure what they were thinking with that stupid spring. I just looked at a few...
No, it's the way to go for sure. I am not sure what they were thinking with that stupid spring. I just looked at a few of the two stroke road race bikes and none of them have spring.

The picture below is what I ended up with for cable adjustment. The left is slammed all the way in, this is important in addition to the tension. Believe it or not, there is 3 HP hiding in the cable adjustment.



Thanks! I just don't see the cables getting that much slack in them if adjusted properly. How much tension are you putting on the right cable to make sure all of the slack is out of it?
captmoto
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captmoto 5/26/2016 11:08am
5/26/2016 11:08am
blackdiamond wrote:
No, it's the way to go for sure. I am not sure what they were thinking with that stupid spring. I just looked at a few...
No, it's the way to go for sure. I am not sure what they were thinking with that stupid spring. I just looked at a few of the two stroke road race bikes and none of them have spring.

The picture below is what I ended up with for cable adjustment. The left is slammed all the way in, this is important in addition to the tension. Believe it or not, there is 3 HP hiding in the cable adjustment.



Share some details!! What kind of slack are you running in the right cable? Where is the HP, on top, mid, spread out?
blackdiamond
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blackdiamond 5/26/2016 12:13pm
5/26/2016 12:13pm Edited Date/Time 5/26/2016 12:28pm
captmoto wrote:
Share some details!! What kind of slack are you running in the right cable? Where is the HP, on top, mid, spread out?
Mostly from mid to top in regards to the power gains. I haven't pinpointed why, but there is a weird correlation between the indexing of the servo motor and what the bike likes on the dyno. It's not just about cable tension. I run just enough cable tension to keep the slack out but not too much that it creates drag.
bvm111
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bvm111 5/26/2016 12:31pm
5/26/2016 12:31pm
bvm111 wrote:
Let me know i am down as well...when and where!!!

That would be a lot of fun just to get together and ride!
blackdiamond wrote:
I've got a tweaked ankle right now so it'll be up few weeks before I get back to the track anywhere. In fact I decided to...
I've got a tweaked ankle right now so it'll be up few weeks before I get back to the track anywhere. In fact I decided to pass on going to spectate the national because it would be too much of a chore to try to hike around all day with this injury the way it is right now. I will keep you posted though.
BD I am actually starting to talk myself out of driving down this Saturday for the national... so I might not be there either.

I have a new suspension setting from Racetech I want to install both fork and shock and I probably could do top end even though the KX has been sitting since January before coming down to ride... although It was running great in Phoenix when I rode it there.

for sure let me know, I have never ridden down that way and would love to come ride GH, Pala.... anywhere actually!!!!
emifrancy 5/26/2016 2:26pm
5/26/2016 2:26pm
emifrancy wrote:
Please, do you nave sane suggestions about the Keihin carb setting? Needle..ecc?
Many thanks!!
blackdiamond wrote:
What carb are you running?
Thank You for your response. I have the PWK KEIHIN carb Yamaha yz 250 2006 version. The needle is: NECJ (second of the top), main 180 and 42 min. I have the boyesen complete kit and "messico" pipe...witch kind of needle do you use?

Thanks again
emifrancy 5/26/2016 2:28pm
5/26/2016 2:28pm
emifrancy wrote:
Please, do you nave sane suggestions about the Keihin carb setting? Needle..ecc?
Many thanks!!
blackdiamond wrote:
What carb are you running?
emifrancy wrote:
Thank You for your response. I have the PWK KEIHIN carb Yamaha yz 250 2006 version. The needle is: NECJ (second of the top), main 180...
Thank You for your response. I have the PWK KEIHIN carb Yamaha yz 250 2006 version. The needle is: NECJ (second of the top), main 180 and 42 min. I have the boyesen complete kit and "messico" pipe...witch kind of needle do you use?

Thanks again
...sorry, I confirm that the TPS working , and the power jet don't working..thanks again
cslacker
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cslacker 5/26/2016 2:44pm
5/26/2016 2:44pm
emifrancy wrote:
Please, do you nave sane suggestions about the Keihin carb setting? Needle..ecc?
Many thanks!!
blackdiamond wrote:
What carb are you running?
emifrancy wrote:
Thank You for your response. I have the PWK KEIHIN carb Yamaha yz 250 2006 version. The needle is: NECJ (second of the top), main 180...
Thank You for your response. I have the PWK KEIHIN carb Yamaha yz 250 2006 version. The needle is: NECJ (second of the top), main 180 and 42 min. I have the boyesen complete kit and "messico" pipe...witch kind of needle do you use?

Thanks again
I personally a big fan of the Suzuki NEDW needle and the JD red needle. The NEDW has a very smooth pull whereas the JD red needle will be snappy off the bottom with a nice hit in the middle.

My setups that I have used are:

42 pilot, NEDW 3rd clip, 172 main

45 pilot, JD Red needle 3rd clip, 175 main
1
blackdiamond
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blackdiamond 5/26/2016 3:42pm
5/26/2016 3:42pm
emifrancy wrote:
Please, do you nave sane suggestions about the Keihin carb setting? Needle..ecc?
Many thanks!!
blackdiamond wrote:
What carb are you running?
emifrancy wrote:
Thank You for your response. I have the PWK KEIHIN carb Yamaha yz 250 2006 version. The needle is: NECJ (second of the top), main 180...
Thank You for your response. I have the PWK KEIHIN carb Yamaha yz 250 2006 version. The needle is: NECJ (second of the top), main 180 and 42 min. I have the boyesen complete kit and "messico" pipe...witch kind of needle do you use?

Thanks again
I am running a JD red needle in the 4th clip position, 168-170 main, 48 pilot
Michael Scott 5/26/2016 4:21pm
5/26/2016 4:21pm
BD, since we're on the topic of carbs, did you ever consider the Lectron?
blackdiamond
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blackdiamond 5/26/2016 10:04pm
5/26/2016 10:04pm Edited Date/Time 5/26/2016 10:04pm
Michael Scott wrote:
BD, since we're on the topic of carbs, did you ever consider the Lectron?
No, for every story I hear about that carb being great and a "huge improvement" I hear 10 more stories that sound like a total nightmare. It's pretty tough to beat the short body Keihin air-stryker for ease of jetting and throttle response (my opinion of course)
emifrancy 5/28/2016 1:33pm
5/28/2016 1:33pm Edited Date/Time 5/28/2016 1:49pm
cslacker wrote:
Any issues with running the 2 right side RC Valve cables yet? Honda was claiming they had the spring on the left side to automatically take...
Any issues with running the 2 right side RC Valve cables yet? Honda was claiming they had the spring on the left side to automatically take up slack but just looking at the setup it really doesn't do that. I bought 2 right side to give it a shot after looking at this.
blackdiamond wrote:
No, it's the way to go for sure. I am not sure what they were thinking with that stupid spring. I just looked at a few...
No, it's the way to go for sure. I am not sure what they were thinking with that stupid spring. I just looked at a few of the two stroke road race bikes and none of them have spring.

The picture below is what I ended up with for cable adjustment. The left is slammed all the way in, this is important in addition to the tension. Believe it or not, there is 3 HP hiding in the cable adjustment.



Hi Blackdiamond, today I tried with the RC right cable also in left side, but It is little bit short..do you made other modify for mounting and set up the left cable?

Another thanks!!
blackdiamond
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blackdiamond 5/28/2016 2:02pm
5/28/2016 2:02pm
No mine fits fine, it is barely long enough but it makes it by about 3mm.

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