02 cr125 dyno

steve125

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Ive spent the last 2 weeks on a 02 cr125 and after some jetting and reed mods it was off to the dyno! Stock with jetting and 50/50 race gas it has a solid 32hp @ 11k rpm. I didn't like the look of the stock honda reed manifold,the bike has a 36mm carby but Honda restricts it down to a rectangle of 26mm x 31mm before opening into the reed cage. So i mounted a 00yz125 reed manifold up to the honda cage and installed 00yz reeds. the 00yz 125 manifold measures 32mm x 37mm. It felt great on the track and the dyno backed that up with a 1hp gain starting at 9k with more over rev! No loss was felt below 9k on the track or did it show on the dyno. We also dynoed a delta 2 with a matched 00 honda manifold and it mirrored the Yam set up with the same hp of 33@11k with just a little extra over rev after peak. This is a great bike thats being held back by poor tuning from Honda,alot of people will pass this bike by due to poor engine performance (stock) and what the mags will say about that! I'll post the spec details soon.;)
 
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#2
Thanks for the useful info. Steve! The mags sure did overlook the cr125 last
year due to the motor- even though I think it has the best of everything else.
Ergos, chassis, suspension, clutch, quality are top notch but the mags still
gave it a mediocre score due to lower peak HP numbers than the others. Can you imagine having this bike with a 2mm overbore by Gorr and MX-tech suspenders? I'm drooling.
 

steve125

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Ok here's the specs thats working for me now. jetting 80degrees,close to sea level,humidity 60-100%. 350main(400stock) 00yz125stdneedle 3rdclip (very close to stock Honda needle profile but has a slightly leaner(larger tip taper and the straight section is a 75 vs a 74 that is honda stock) 25pilot air screw at 2 out with no idle! The jetting is very crisp and clean. Fuel is VPmr2 50/50 with sunoco94 ( For me the 50/50 has the best "hit" into the power band vs straight mr2 which is smoother)....A 00 yz125 drilled to fit manifold with 00yz reeds also drilled to fit. The manifold fingers fit perfect into the stock cr cage and the carb angle is the same. Both this setup and the 00 delta2 clearly out perform stock and i will test both on the track and pick the one i like. With good jetting and fuel and the reed mod this motor is as good as (in the mid) and better (on top and over rev) than my stock 01 yz125! The hp is just hideing, it's the best honda motor in years!
 
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HLT

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#4
Steve, I haven't gotten to play with an '02 yet, but on the '00-'01 CRs, a YZ airboot helped a lot also. It took some doing to make it fit, but for hardcore racing, it was worthwhile.
 
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MikeT

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#5
Steve, this may be a silly question but, is that HP at the crank or rear wheel? Second do you mount a street tire on the bike when you run it on the dyno or use the knobby?
 

steve125

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#7
The air boot that HLT is talking about is off a yz125,it's that big black boot that connects the carby to the air box. I'm sure it would take some work to make it fit like he says! For 02 honda seems to have taken care of the air boot problem of the earlier models.Many changes have been made from the air boot back to the air filter and air box itself to increase air flow. As far as the dyno goes we have a street tire mounted on a cr rear wheel, the dyno measures rear wheel HP. Mike T no question is silly! we are all here to help each other:cool:
 

cr-man

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#8
What's next for your Honda 125?

Steve125 what do you have planned next for your 125? I was out at the practice track I ride on and a guy was there on an 02 Honda 125 and I must say I was pretty impressed the bike sounded Healthy and left corners with authority! I love the way the thing looks like a feather weight and thin! I don't think it was as fast as my 99 YZ 133, but I don't think it was far behind. Steve let me know what kind of ring life your getting on your CR as I only get about 8 to 10 hours max on my YZ. I've heard the KTM guys get at least 25 hours and are making more power than I have.:think
Thanks Joe
 

steve125

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#9
Joe we have a pc pipe and sliencer coming in the next week or so. The bike is running so strong right now i don't expect any big gains from the pipe. Honda pipes are tough to beat. Ive been testing the reed valve combos at the track this weekend and it's been a tough decision. I'm going with the delta for now,the best throttle response and low end with great over rev!....But.....the yam set up hits hard and pulls hard up to peak and with carbon reeds the over rev is very close to the delta. Either valve the bike just rips! Remember i'm using the 00 delta set up for a larger reed opening from the manifold, the 01-02 delta's inlet holes are smaller to match their manifolds.:D
 

MikeT

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#10
Originally posted by steve125
As far as the dyno goes we have a street tire mounted on a cr rear wheel, the dyno measures rear wheel HP. Mike T no question is silly! we are all here to help each other:cool:
Wow 33 at the rear wheel. That's pretty good. Thanks Steve.
 
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#11
hey steve

thanx alot for all that information. i was just starting to read about the new 2002 CR 125's i have a 00 YZ 125 and i love it but it is about time for me to get a new one. and i was really looking towards the CR cause they do look so light and thin and from all of the changes they are doing to them it looks like they might be fast and they might just haul and pull from the corners which is very much to my liking. I am not the best rider in the world so i love that bottom end power so i can get out of the corner and still make it over the jump without berming the corner like the pros because im just not that fast yet. So please tell me what u think about what the CR has for low end or what anyother bikes have for low end? Thanks alot Steve.
 
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#12
33 hp, ha, my new KX makes 38 according to Tom Morgan!;) :scream: But honestly, I wqas having a talk with a local expert about what he did to his CR to make it really fast and it was all alot of little stuff like you say. A change here and a little bit of grinding there and the thing rips.
 

MikeT

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#13
Steve, let me ask another question. My bikes certificate of origin says it makes 39 hp (1996 YZ125) That must be at the crank, right? How much power is usually lost going to the rear wheel? I mean if your bike has 33 at the rear wheel, how much should it have at the crank. I know differences in drive trains will make a difference but most 125's are pretty similar so all I want to know is a ball park number if you can.

Mike
 
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#14
Originally posted by steve125
As far as the dyno goes we have a street tire mounted on a cr rear wheel, the dyno measures rear wheel HP.
Thanks for all the insights you provided, but I'd like to ask what kind of a tire you have back there. Is there a fairly common street tire size that fits a 19" rear MX wheel or are you using one of the less knobby dual-sport tires?

I now have a YZ250 that I can jet in the ballpark, but I'm looking at a KTM 520 SX and I think I'll need to get it on a dyno (or get a lambda sensor in the header but that's another topic altogether) to get the jetting right.
 
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#15
hey steve,,,do you know any secrets into adding more HP into the 99 CR125?? Since I can't afford a new bike, should I at least buy a 00 or 01? Thanks!