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Grand Master

Tony477g

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A 125 has way more power than any 85, you're 5'3'' 110 lbs, if you're thinking anyone will recommend a 450 or 250 2t you're out of your mind. It sounds like you've only ridden an 85 and with reeds and a pipe its not going to make the bike any faster, maybe a negligible amount but no where near the power of a 125. My recommendation get a 125.

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Grand Master

SilvFx

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A 125 has way more power than any 85, you're 5'3'' 110 lbs, if you're thinking anyone will recommend a 450 or 250 2t you're out of your mind. It sounds like you've only ridden an 85 and with reeds and a pipe its not going to make the bike any faster, maybe a negligible amount but no where near the power of a 125. My recommendation get a 125.

 

I keep hearing this from people, but its simply not true.  YZ85/KX85/KX100/RM100/RM85/KTM85/CR85, etc all have 27-29 hp and usually six speed transmissions.  Their weight is approx. 150 lbs.  KX125/RM125/YZ125, etc are rated at 33-35 hp and weigh approx 200-210 lbs.  On a lbs/hp basis the little two strokes have a negligible advantage.

 

125 2 stroke performance isn't significantly different given the higher weight of the 125 (largely due to bigger components all around). In addition, the 125 sits a whole lot higher than the 85s/100s.  At 5' 3", I think a full size bike is gonna be tough to manage.  I would say move up to KX100, KTM 105 SX or CRF150RB.  No problem with a 125 if you can deal with the height, but my guess is you will need to lower it and I don't think you will see a significant increase in performance.  You would have to move up to 200 or 250 two stroke for that.

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Grand Master

Tony477g

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YZ125 34.01 horsepower wet weight a little under 200 pounds. There is no way an 85 is hitting 27-29 HP maybe 20-25 max, and that 25 is in a special category for new bikes with 157lb wet weight. if you think 10 horsepower isn't a huge power advantage jump on a crf250r then jump on a crf450r and tell me its a negligible advantage. 

 

I keep hearing this from people, but its simply not true.  YZ85/KX85/KX100/RM100/RM85/KTM85/CR85, etc all have 27-29 hp and usually six speed transmissions.  Their weight is approx. 150 lbs.  KX125/RM125/YZ125, etc are rated at 33-35 hp and weigh approx 200-210 lbs.  On a lbs/hp basis the little two strokes have a negligible advantage.

 

125 2 stroke performance isn't significantly different given the higher weight of the 125 (largely due to bigger components all around). In addition, the 125 sits a whole lot higher than the 85s/100s.  At 5' 3", I think a full size bike is gonna be tough to manage.  I would say move up to KX100, KTM 105 SX or CRF150RB.  No problem with a 125 if you can deal with the height, but my guess is you will need to lower it and I don't think you will see a significant increase in performance.  You would have to move up to 200 or 250 two stroke for that.

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Grand Master

SilvFx

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YZ125 34.01 horsepower wet weight a little under 200 pounds. There is no way an 85 is hitting 27-29 HP maybe 20-25 max, and that 25 is in a special category for new bikes with 157lb wet weight. if you think 10 horsepower isn't a huge power advantage jump on a crf250r then jump on a crf450r and tell me its a negligible advantage. 

 

Tony, owned a 09 KX100...says 29 hp right on the manufacturer's certificate of origin.  Owned an '07 YZ85, that one said 27 hp right on the manufacturers certificate of origin.  Not sure what it says on a YZ125 manufacturers certificate of origin.   Or, if the 34.01 hp you quoted is measured at the countershaft sprocket or rear wheel or is measured the same way as the HP shown on the manufacturers certificate of origin.  But, here are the facts as I know them:

 

2009 KX100, wet weight 156.5 lbs.  156.5/29 = 5.40 lbs/max hp

2007 YZ 85, dry weight 146 lbs + 7.8 estimated fluids = 154 lbs/27 = 5.703 lbs/max hp

 

2007 YZ125, dry weight 190 lbs +12.6 estimated fluids = 203 lbs/34.01 = 5.97 lbs/max hp

2009 YZ125, wet weight 208 lbs.  208/34.01 = 6.11 lbs/max hp

2014 YZ125, wet weight 207 lbs.  207/34.01 = 6.09 lbs/max hp

 

For the YZ125 to have the same lbs/max hp ratio as the KX100, manufacturers certificate of origin would have to say 38.5 hp (208/38.5 = 5.40 lbs/max hp

 

Not sure what the torque or HP curves look like of each but based on the published specs, these 85/100 cc two strokes have very low lbs per hp and are comparable to the 125 two strokes lbs/max hp rating.  And, I can tell you from personal experience riding my kids' YZ85/KX100 (even at my 170 lbs) that they rip and are very fast if ridden on the pipe.  This was very surprising to me and I think surprising to a lot of folks that casually recommend 85 two strokes to newbies without realizing that these things are every bit the race bike that the 125 2 stroke is.

 

The difference between 450 and 250 4 stroke is huge and is further exacerbated by the difference in torque.  I don't think comparing and 85/100 cc two stroke to a 125cc two stroke is in any way similar to comparing a 250 vs 450 4 stroke MX bike.

 

Without further derailing the original poster's thread, my only point was the performance difference between the 85/100 and 125 is not much and if they somehow thought the 85 was slow and boring (which I have a tough time believing) that the 125 wont be much different - just a lot taller and more to throw around for someone who is 5' 3"

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88cr80

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Tony, owned a 09 KX100...says 29 hp right on the manufacturer's certificate of origin. Owned an '07 YZ85, that one said 27 hp right on the manufacturers certificate of origin. Not sure what it says on a YZ125 manufacturers certificate of origin. Or, if the 34.01 hp you quoted is measured at the countershaft sprocket or rear wheel or is measured the same way as the HP shown on the manufacturers certificate of origin. But, here are the facts as I know them:

2009 KX100, wet weight 156.5 lbs. 156.5/29 = 5.40 lbs/max hp

2007 YZ 85, dry weight 146 lbs + 7.8 estimated fluids = 154 lbs/27 = 5.703 lbs/max hp

2007 YZ125, dry weight 190 lbs +12.6 estimated fluids = 203 lbs/34.01 = 5.97 lbs/max hp

2009 YZ125, wet weight 208 lbs. 208/34.01 = 6.11 lbs/max hp

2014 YZ125, wet weight 207 lbs. 207/34.01 = 6.09 lbs/max hp

For the YZ125 to have the same lbs/max hp ratio as the KX100, manufacturers certificate of origin would have to say 38.5 hp (208/38.5 = 5.40 lbs/max hp

Not sure what the torque or HP curves look like of each but based on the published specs, these 85/100 cc two strokes have very low lbs per hp and are comparable to the 125 two strokes lbs/max hp rating. And, I can tell you from personal experience riding my kids' YZ85/KX100 (even at my 170 lbs) that they rip and are very fast if ridden on the pipe. This was very surprising to me and I think surprising to a lot of folks that casually recommend 85 two strokes to newbies without realizing that these things are every bit the race bike that the 125 2 stroke is.

The difference between 450 and 250 4 stroke is huge and is further exacerbated by the difference in torque. I don't think comparing and 85/100 cc two stroke to a 125cc two stroke is in any way similar to comparing a 250 vs 450 4 stroke MX bike.

Without further derailing the original poster's thread, my only point was the performance difference between the 85/100 and 125 is not much and if they somehow thought the 85 was slow and boring (which I have a tough time believing) that the 125 wont be much different - just a lot taller and more to throw around for someone who is 5' 3"

How come my CRF150R only says 23.5??? My 150 is more powerful than all the 85's I've driven.

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Grand Master

BushPig

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Lol, still thinking about how experienced a kid riding a 85 really has...

LOL he said he rode one, not that he owns and rides one.

I wonder the same, "an experienced rider" that find CR85s "slow" at 5'3" would be racing a supermini I would have thought....

Edited by BushPig
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Jrs Turn

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Not really.Would be too tall for anyone under 5'6'. I'm 5'7" and have a low seat to make it more manageable.

Interesting. I knew a girl while racing D36 that was maybe 5'4"ish in boots and rode hers just fine. I didn't notice any drastic lowering work done on it but maybe there was some suspension trickery in there. I do know that's it's a neat displacement for smaller riders that want to get down. ?

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Grand Master

BushPig

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Interesting. I knew a girl while racing D36 that was maybe 5'4"ish in boots and rode hers just fine. I didn't notice any drastic lowering work done on it but maybe there was some suspension trickery in there. I do know that's it's a neat displacement for smaller riders that want to get down. ?

Same size as any other ktm full size bike. If it wasn't its been lowered. I didnt say it couldn't be done but they aren't short bikes.

Edit; not trying to be smart here, I have a KTM 200EXC and I can say for a fact it will be a tall bike for someone at 5'2". Stock it was tall for me fir technical rides and I'm 5'7" .

Edited by BushPig
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Jrs Turn

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Same size as any other ktm full size bike. If it wasn't its been lowered. I didnt say it couldn't be done but they aren't short bikes.

Edit; not trying to be smart here, I have a KTM 200EXC and I can say for a fact it will be a tall bike for someone at 5'2". Stock it was tall for me fir technical rides and I'm 5'7" .

No worries. I wonder if it's a year thing then. I would guess hers was around an 05' maybe? I recall sitting on it and the cockpit feeling small, almost like a 125 which got me thinking about buying one. I prefer that smaller frame feel ( of the 125's) but love the power of the 250. Either way the 200 is a neat bike.

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Grand Master

BushPig

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No worries. I wonder if it's a year thing then. I would guess hers was around an 05' maybe? I recall sitting on it and the cockpit feeling small, almost like a 125 which got me thinking about buying one. I prefer that smaller frame feel ( of the 125's) but love the power of the 250. Either way the 200 is a neat bike.

 

older versions did use 125 frames. To clarify, I call a 125 a full size frame.

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Grand Master

SilvFx

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How come my CRF150R only says 23.5??? My 150 is more powerful than all the 85's I've driven.

 

Not sure.  Sounds like a good research project for a promising young engineer/science geek.

 

I suggest you contact each of the manufacturers and speak with all engineers and all the other employees associated with how they go about determining and reporting the hp readings to be included on the manufacturer's certificate of origin and if it has every changed over time?  Be sure to report back here, laying out exactly what you find from each complete with flowcharts of the process and contributors.  Next, commission a 'real world' study where you are randomly sampling dozens of these bikes (of various model years) and running them on a dynamometer to get thieir hp readings.  And, then you can publish those results with a comparison of reported hp on the MSO's vs. a 'real world' sampling and identify any discrepancies, under-reporting, and over reporting by manufacturer.

 

Or, you can just smugly assure us all that your CRF150R is way more powerful than all the 85's you have driven....it's your call.

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