Full Tilt CR250 Build - MXA Two Stroke Hall of Fame

MXandSXracer21 4/22/2016 6:35am
4/22/2016 6:35am
H4L wrote:
Do the 09-12 CRF450r clamps bolt up to the 02-07 CR250r chassis with no modifications ? Thanks.
Yes they do, however, you need to use the correct lower stem bearing since it is different on the 09-12 models. The lower bearing is the same as 02-07 CR125/250 on 13+ triple clamps though
blackdiamond
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blackdiamond 4/22/2016 12:25pm
4/22/2016 12:25pm
Tokyo_Tiddler wrote:
Just wondering, but are you also watching what is happening to your torque curve? Horsepower is a function of torque. I have always heard that while...
Just wondering, but are you also watching what is happening to your torque curve? Horsepower is a function of torque. I have always heard that while horsepower reflects potential for speed, it is torque that determines acceleration. We all like horsepower for bragging rights, but it is really the torque that is the most interesting. For drag racing engines, hp is an indicator for MPH potential, while tq is a better indicator for ET potential. Torque is what you feel in the seat of your pants. For an MX bike, a broad, smooth, strong torque curve is what I have always sought after.
Here is one of the dyno runs overlaid with a stock RMZ450. The two stroke actually makes a bit more peak torque.



H4L
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H4L 4/22/2016 4:21pm
4/22/2016 4:21pm
MXandSXracer21 wrote:
Yes they do, however, you need to use the correct lower stem bearing since it is different on the 09-12 models. The lower bearing is the...
Yes they do, however, you need to use the correct lower stem bearing since it is different on the 09-12 models. The lower bearing is the same as 02-07 CR125/250 on 13+ triple clamps though
Thanks for the info.

The Shop

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40
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40 4/24/2016 5:52pm
4/24/2016 5:52pm Edited Date/Time 4/24/2016 6:08pm


PR2 comparison again just for convenient reference. The Varner setup looks better at the 4500 rpm hole, makes equal or more power thru about 7200 rpm, and is broader and appears easier to ride. Interestingly, the Varner appears to peak around 700 rpm earlier than the PR2, maybe a result of the base milling.
blackdiamond
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blackdiamond 4/27/2016 3:14pm
4/27/2016 3:14pm
40 wrote:
[img]http://i1193.photobucket.com/albums/aa346/RC250R/PR2CR250dyno_zpsaadfe98a.jpg[/img] PR2 comparison again just for convenient reference. The Varner setup looks better at the 4500 rpm hole, makes equal or more power thru about 7200...


PR2 comparison again just for convenient reference. The Varner setup looks better at the 4500 rpm hole, makes equal or more power thru about 7200 rpm, and is broader and appears easier to ride. Interestingly, the Varner appears to peak around 700 rpm earlier than the PR2, maybe a result of the base milling.
You are missing the fact that the Varner engine has almost 4 more HP more at 7000 RPM and that is an extremely important area of the power-band (unless you are road racing) The reason everyone complained about the CR250 was the bottom end, not the top end.

If you rode the two engines back to back on the track, the quality of the spread will do far more for the lap times than bragging rights on the dyno I can assure you. Getting big peak numbers is much easier than creating a power-band that is linear and usable much like a four stroke. I think with a second day in the dyno room we could make some more progress but after riding it in the dirt I think it's almost pointless. It's so broad and strong right now that it is head and shoulders better than anything I have had before and I have had some really fast two strokes over the years from many different tuners.
Underground 4/27/2016 3:24pm
4/27/2016 3:24pm
40 wrote:
[img]http://i1193.photobucket.com/albums/aa346/RC250R/PR2CR250dyno_zpsaadfe98a.jpg[/img] PR2 comparison again just for convenient reference. The Varner setup looks better at the 4500 rpm hole, makes equal or more power thru about 7200...


PR2 comparison again just for convenient reference. The Varner setup looks better at the 4500 rpm hole, makes equal or more power thru about 7200 rpm, and is broader and appears easier to ride. Interestingly, the Varner appears to peak around 700 rpm earlier than the PR2, maybe a result of the base milling.
Without seeing all off BD's dyno sheets, I'd be more inclined to think that they were able to fill the dip by opening the PV sooner with the adjustable PV mapping
blackdiamond
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blackdiamond 4/27/2016 9:20pm
4/27/2016 9:20pm
Underground wrote:
Without seeing all off BD's dyno sheets, I'd be more inclined to think that they were able to fill the dip by opening the PV sooner...
Without seeing all off BD's dyno sheets, I'd be more inclined to think that they were able to fill the dip by opening the PV sooner with the adjustable PV mapping
Opening it sooner can actually make a bigger hole in some cases and it's really tricky ironing out the weak spots. It takes a lot of trial and error.

The two curves have nothing in common whatsoever in regards to the shape and rideability. Its like a light switch compared to a tractor.
Underground 4/28/2016 2:50am
4/28/2016 2:50am
Underground wrote:
Without seeing all off BD's dyno sheets, I'd be more inclined to think that they were able to fill the dip by opening the PV sooner...
Without seeing all off BD's dyno sheets, I'd be more inclined to think that they were able to fill the dip by opening the PV sooner with the adjustable PV mapping
blackdiamond wrote:
Opening it sooner can actually make a bigger hole in some cases and it's really tricky ironing out the weak spots. It takes a lot of...
Opening it sooner can actually make a bigger hole in some cases and it's really tricky ironing out the weak spots. It takes a lot of trial and error.

The two curves have nothing in common whatsoever in regards to the shape and rideability. Its like a light switch compared to a tractor.
Yeah I can see that in the peakiness of the both PR2 curves and how steeply they climb. Nice dirt track engine though.
Having the benefit of the dyno, were you able to change the opening time and speed of your PV to achieve that seamless curve and retest, which is were I imagine you spent a lot of your time?
Underground 4/28/2016 2:52am
4/28/2016 2:52am
Also the how closely the peak HP and torque points are in the rev range indicates how PR2 engine is going to sing
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blackdiamond 4/28/2016 1:02pm
4/28/2016 1:02pm
Underground wrote:
Yeah I can see that in the peakiness of the both PR2 curves and how steeply they climb. Nice dirt track engine though. Having the benefit...
Yeah I can see that in the peakiness of the both PR2 curves and how steeply they climb. Nice dirt track engine though.
Having the benefit of the dyno, were you able to change the opening time and speed of your PV to achieve that seamless curve and retest, which is were I imagine you spent a lot of your time?
Yea, that part was really tricky and I think we could still improve on it. I have 7 RPM points programmed on the PV map and we made tweaks as small as 2% increments (55% open at 5400 RPM vs 57% open at 5400 RPM for example) to get the results we have now.

It amazed me how sensitive the engine is to power-valve tuning but it makes an amazing, broad engine if you have the patience to keep tweaking on it. I just ran out of time that night but we have another dyno session planned in the future to see if we can wring a bit more out of it.
blackdiamond
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blackdiamond 4/28/2016 1:03pm
4/28/2016 1:03pm
Underground wrote:
Also the how closely the peak HP and torque points are in the rev range indicates how PR2 engine is going to sing
It would be tough to ride, no doubt about it.
40
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40 4/28/2016 3:39pm
4/28/2016 3:39pm
blackdiamond wrote:
It would be tough to ride, no doubt about it.
I have not ridden the PR2 engine, but a friend did and he said it was a monster. He used other tuners for his future CR250 engines.
Interestingly, if you call PR2, they say this dyno is the same setup that they built for Team Blackfoot.
blackdiamond
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blackdiamond 4/28/2016 3:52pm
4/28/2016 3:52pm
I've had engines like that before, they don't work out so well unless you're Ricky Carmichael
Underground 4/28/2016 5:38pm
4/28/2016 5:38pm Edited Date/Time 4/28/2016 5:39pm
blackdiamond wrote:
I've had engines like that before, they don't work out so well unless you're Ricky Carmichael
Or Barcia
Underground 4/28/2016 5:45pm
4/28/2016 5:45pm
Does that engine have the gear position sensor? I'm thinking at least the moulding? There be a bunch more dyno hours for each gear if the CDI will allow. It would be interesting to get some of the old Honda guys from RC days to weigh in on the build and what they had and to compare. I'm thinking your probably pretty darn close.
Underground 4/28/2016 5:47pm
4/28/2016 5:47pm
Dave Arnold is no longer tied up I think? Gibby?
blackdiamond
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blackdiamond 4/28/2016 5:54pm
4/28/2016 5:54pm Edited Date/Time 4/28/2016 5:55pm
Underground wrote:
Does that engine have the gear position sensor? I'm thinking at least the moulding? There be a bunch more dyno hours for each gear if the...
Does that engine have the gear position sensor? I'm thinking at least the moulding? There be a bunch more dyno hours for each gear if the CDI will allow. It would be interesting to get some of the old Honda guys from RC days to weigh in on the build and what they had and to compare. I'm thinking your probably pretty darn close.
I think it is available but I am not 100% certain. Things are already pretty complicated when you are programming 3 different ignition curves based on throttle position, PV mapping and 3D power-jet parameters as well.

Pit Row

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Underground 4/28/2016 8:46pm
4/28/2016 8:46pm
Underground wrote:
Does that engine have the gear position sensor? I'm thinking at least the moulding? There be a bunch more dyno hours for each gear if the...
Does that engine have the gear position sensor? I'm thinking at least the moulding? There be a bunch more dyno hours for each gear if the CDI will allow. It would be interesting to get some of the old Honda guys from RC days to weigh in on the build and what they had and to compare. I'm thinking your probably pretty darn close.
blackdiamond wrote:
I think it is available but I am not 100% certain. Things are already pretty complicated when you are programming 3 different ignition curves based on...
I think it is available but I am not 100% certain. Things are already pretty complicated when you are programming 3 different ignition curves based on throttle position, PV mapping and 3D power-jet parameters as well.

Shit yeah there be some hours. But when your in this deep .......Maybe later down the track when you go looking for some more over rev in 4th and better traction/roll on in 2nd.
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blackdiamond 4/28/2016 8:50pm
4/28/2016 8:50pm
I was surprised but it will actually go 68-70 miles per hour in fourth gear now! I didn't think it would be that fast on top.
emifrancy 4/28/2016 11:18pm
4/28/2016 11:18pm
blackdiamond wrote:
Here's a cool pic I took tonight of the bare chassis [img]https://p.vitalmx.com/photos/forums/2016/03/20/128752/s1200_20160320_194712.jpg[/img]
Here's a cool pic I took tonight of the bare chassis



Hi Blackdiamond!!your bike is amazing!! Please, one question: which kind of linkage and rear shock absorber do you use??

Many thanks!!!
blackdiamond
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blackdiamond 4/28/2016 11:45pm
4/28/2016 11:45pm
Linkage is stock, the rear shock is more complicated. See below.

2015 Honda CRF450 rear shock

Graeme Brough valving and set up
Kashima coated shock body
SDI works shock clevis with additional rebound adjuster
KYB A-kit shock shaft
Oversize bladder cap
Works aluminum pre-load collars
RCS titanium shock spring
Works check-valve/rebound separator
Low friction piston band
Works KYB low friction shock seal head
Kawasaki-rider 4/28/2016 11:57pm
4/28/2016 11:57pm
How did you manage to fit the shock? I tried a -14 crf 450 on mine and it rubs against the airbox..Smile
blackdiamond
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blackdiamond 4/29/2016 12:52am
4/29/2016 12:52am
Slight mod to the sub-frame and airbox. You have to be really careful and be sure to cycle the shock all the way through the stroke when doing this mod to ensure proper clearance. The shock rotates up and back as it compresses making the clearance issue even worse and you have to factor in flex, etc. as well.
emifrancy 4/29/2016 3:31am
4/29/2016 3:31am
Thank you very much!! I have one shock of crf 450 2015 but it is little bit short. Only one thinks, the original is 500 mm (hole to hole) but the Crf model is 495 mm..
blackdiamond
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blackdiamond 4/29/2016 3:41am
4/29/2016 3:41am
The 2009-2012 shocks are about 14mm longer (?) and you could shorten it slightly to get the correct length? That would probably be a lot easier way to go.
emifrancy 4/29/2016 3:52am
4/29/2016 3:52am
To night when I came back to home, I send one photo about the length of the shock
emifrancy 4/29/2016 11:11pm
4/29/2016 11:11pm




This is my modify about RC valve cover...is in plexiglass 5mm. Today I try with BLAKDIAMOND modify about the right rc motor cable also in left side..
1
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ledger 4/29/2016 11:17pm
4/29/2016 11:17pm
dbrunski125 wrote:
https://www.instagram.com/p/BEw3y6LQrJa/

I guess we know who is testing this bad boy ouy! Wink
Great find db125 ! Very cool and 110% deserved. Congrats blackdiamond, and also to everyone else that made this bike into a moto-masterpiece, top shelf build would be an understatement. All we need now, is for Honda to take note's and deliver to the showroom floor's. Woohoo

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