is there much difference between a 85 and a 125

[ikeC]

hi just wandering as a whole if there really is much difference performance wise between an 85 and a 125 e.g ktm 85 sx and the 125 ?? or is there anythimg between these 2 stroke or 4 stroke

[Theeebalz]

a 125 will have a wider power band than an 85, better suspension (more travel) higher ground clearance, and not much heavier! the 85 will range 19-24ish horses while the 125 lets say a kx125 has about 41 hp.

the 125 will also have more low end, they don't have much but it's not a lightswitch like the 85!

[suzukid]

The 85 is a little bike. I'm 5'4 so I love the smaller 85's as I can acually touch the ground and flick it around pretty good. I had a RM85 with diffrent gearing and I could hang in there with any 125 out there. But I'm also really light at 115lbs so a 85 hauls me around pretty well lol. It really depends on how much you weigh and how tall you are. If your heavier the and taller the 125 is the way to go, but the best thing is to take each for a ride and see what you like better.

[ikeC]

I am about the same as you in height and weight so, but yh i will try both,thanks

[suzukid]

If your like me your going to find the 85 lacks in the power but the 125 is just too tall.. maybe somthing like a rm or kx100 or if its possible a lowered 125

[moto_rider7755]

a 125 will have a wider power band than an 85, better suspension (more travel) higher ground clearance, and not much heavier! the 85 will range 19-24ish horses while the 125 lets say a kx125 has about 41 hp.

the 125 will also have more low end, they don't have much but it's not a lightswitch like the 85!

Yammablue, I am curious where you get all of your information. A stock 125 MX bike does not produce 41 hp...closer to 33-35 (screaming at about 12,000 rpm with next to nothing at 2000 rpm). Peak hp for a 125 is comparable to a peak hp for a 250F, just a different power curve. A 2012 YZ 125 weighs 208 lbs wet and a YZ 85 weighs 157 wet...thats a 51 lb difference...which is HUGE. You are correct that the 125 has more fork travel...1" more. The weight and suspension information is on Yamaha's website if you want to check it.

[Theeebalz]

bikez .com that specs site, just looked at peak horse power of an 02. it could be a typo might have meant to say 31., wrote that a while ago..

http://www.bikez.com/motorcycles/kawasaki_kx_125_2002.php that says 39... i might've typo'd not sure

[Cardone]

I'd say 125 because you can ride them longer, if you get the hang of it. I'm 5'6 and around 135 lb, it picks up pretty well. Most everything depends on size though

[moto_rider7755]

Yeah, Ive seen some funny numbers from that bikez website...I wonder where their data comes from....they must be using that magic dyno operated by the tooth fairy mentioned on Dirt Rider a while back. Most of the hp data Ive seen looks alot like the graph in this article...granted, its old (2002), so, maybe add 1-2 hp for newer models

http://www.motorcycle-usa.com/276/525/Motorcycle-Article/2002-Yamaha-YZ125-vs-YZ250F.aspx

[Theeebalz]

yea i've wondered about a couple of their stats, i usually just checked weights heights and such, it seemed weird but i saw a couple other sites like that, i cant find them at the moment... but seemed fishy, maybe modded it could make more but not stock

[funkinalive]

you are BOTH right in your HP figures but forgot to classify your power ratings... brake horsepower or BHP is measured at the crank before any power consumption from the transmission chain and wheel (as well as applicable bearing/sliding friction, hydrodynamic resistance... etc) so 41BHP is a realistic figure. a more useful figure is regular HP measured at the rear wheel which takes into consideration all of the losses occurring between he crank and the ground. which would give an output of around 35hp. as you can imagine normal HP is much more informative than BHP (because BHP is not taking into consideration any mechanical losses from the machanical system as a whole)

[moto_rider7755]

you are BOTH right in your HP figures but forgot to classify your power ratings... brake horsepower or BHP is measured at the crank before any power consumption from the transmission chain and wheel (as well as applicable bearing/sliding friction, hydrodynamic resistance... etc) so 41BHP is a realistic figure. a more useful figure is regular HP measured at the rear wheel which takes into consideration all of the losses occurring between he crank and the ground. which would give an output of around 35hp. as you can imagine normal HP is much more informative than BHP (because BHP is not taking into consideration any mechanical losses from the machanical system as a whole)

The link I included was hp at the crank....take a look. I dont believe 41 hp is accurate for a stock 125 MX bike...I have never seen a figure that high for a 125 in anything I have read.

[Theeebalz]

the link i had just said power, didn't specify... idk it doesn't matter! what bike are you thinking OP?

[funkinalive]

The link I included was hp at the crank....take a look. I dont believe 41 hp is accurate for a stock 125 MX bike...I have never seen a figure that high for a 125 in anything I have read.

reopen your link and please also READ the article and you will find "...cranks out 32.1 rear-wheel horsepower on White Brothers' Dynojet 200 dyno at its peak.

this method is for measuring regular HP, most modern 125 2T will be around 35hp at the wheel, and 40 at the crank

[moto_rider7755]

Here you go...read this...especially the part written by Gene, a seasoned dyno operator. "CRANK Horsepower Est. @ 10,500-11,000 (below are est. on what CRANK h.p. you can get out of certain motor displacements. They are est. because alot depends on how the rest of the motor is set up. The higher you peak it out in rpms the more h.p. (kart Motor)

125cc 32-36

132cc 36-38

144cc 38-41

153cc 41-43+

KTM 125 motor is set up really good out of the box 35-36 est."

https://www.thumpertalk.com/forum/archive/index.php/t-543517.html

[funkinalive]

OK, lets recap to your FIRST link that you posted, that would be http://www.motorcycle-usa.com/276/52...vs-YZ250F.aspx

please READ the 7th paragraph!!! and you will see that the test was measured at the wheel for HP. Im not even arguing with you because YOU POSTED THE DARN LINK!!! second: measuring HP at the rear wheel will ALWAYS get you a lower HP measurement and since your ADDING new sources written by Mr. Gene lets also consider furthur what he says:

"...You can typically take off around 15% for a ballpark fiugre as to what RWHP will be..." his words

im not confirming ANY numbers here i was simply stating that when measuring HP you will get a higher measurement at the crank (obviously) so your HP numbers will be higher. so both yammablue and yourself where technically right just not stating where the HP is coming from. and if you want NUMBERS than lets work off the material YOU provided from the links above, 8th paragraph "...the YZ125 beats out the twice-bigger 250F in peak power, pumping out just one pony more at 33.0 hp..." this of course can be verified from their graph and we also know that paragraph 7 states that its measured at the rear wheel... since Gene says that we should typically add 15% (i believe its more because of the length of a dirtbike's chain) to accommodate for mechanical loses we end up with 33HP+15%(of 33)= 37.95HP

were done here because the smell of piss is in the air...

[Theeebalz]

33HP+15%(of 33)= 37.95HP

were done here because the smell of piss is in the air...

and 37.95 is pretty damn close to a 125, like you said!

[DMC707]

OP, my question is are you an adult or a juvenile? If you are an adult, but on the small side, you should consider getting an adult's bike.

The 125 is an adult sized motorcycle while an 80/85/105 is an adolescent's machine historically

Set it up soft -- and do everything else short guy's have to do -- tip-toes, milk crates, etc.

Once you get it rolling, you won't even think about it. Historically there have been some very very good MX riders that are around your height

[Theeebalz]

yea, do you think RC could touch on a 250 2stroke?

[moto_rider7755]

OK, lets recap to your FIRST link that you posted, that would be http://www.motorcycle-usa.com/276/52...vs-YZ250F.aspx

please READ the 7th paragraph!!! and you will see that the test was measured at the wheel for HP. Im not even arguing with you because YOU POSTED THE DARN LINK!!! second: measuring HP at the rear wheel will ALWAYS get you a lower HP measurement and since your ADDING new sources written by Mr. Gene lets also consider furthur what he says:

"...You can typically take off around 15% for a ballpark fiugre as to what RWHP will be..." his words

im not confirming ANY numbers here i was simply stating that when measuring HP you will get a higher measurement at the crank (obviously) so your HP numbers will be higher. so both yammablue and yourself where technically right just not stating where the HP is coming from. and if you want NUMBERS than lets work off the material YOU provided from the links above, 8th paragraph "...the YZ125 beats out the twice-bigger 250F in peak power, pumping out just one pony more at 33.0 hp..." this of course can be verified from their graph and we also know that paragraph 7 states that its measured at the rear wheel... since Gene says that we should typically add 15% (i believe its more because of the length of a dirtbike's chain) to accommodate for mechanical loses we end up with 33HP+15%(of 33)= 37.95HP

were done here because the smell of piss is in the air...

Thanks, you proved my point...38 is not equal to 41...thanks for the verification.

You also missed this part "125cc 32-36[hp]" from our source, Gene.