01 cr125 no low end power!!
  • stuntrider
    Posts: 2
    Whats going on guys? So I recently started stunting my street bike but decided to pick up a dirt bike to practice alittle. So i bought an 01 cr125 with V-Fource3 reed and a procicuit exaust for 800 bucks! So i started setting up the bike to stunt, up 15 in the rear (68T) and down 1 in the front (12t) but the dike still feels like there is no bottem end. I have to be in the mid to uppers power range to get the tire up. This thing should have crazy bottom end. Thoughts? Ideas?

    Thanks
    Carl
  • markyrocks
    Posts: 1,351
    Try revving the motor up a slipping the clutch
  • EEE299EEE299
    Posts: 678
    Ive never used a bike geared that far off but im assuming your first gear does something like 4.5 miles an hr lol. Its a 125 so even geared down you really aren't changing the engine. 125s are always going to be snappy top end machines, unless you do some serious engine mods. Also your coming off of a street bike where they are like what 600cc? putting out over 100 horses i believe? A tiny little 125cc engine putting out 32-33 horse (if your bikes running good) isnt gonna power wheelie like a 600cc fire breather. On top of that like i said before a 125 motocross bike is not meant to be run at low rpms no matter how you gear it. just out of curiosity how fast does it go now 35-40mph lol
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Yz125 05
    Crf250x 05

    -Evan
  • NZriderNZrider
    Posts: 5,153
    agreed, changing gearing wont change the low RPM power delivery. sounds like you need a 4 stroke if low RPM torque is what you want. either that or a trials bike
    *********************
    Winning is 90% rider and only 5% bike, the rest is luck
  • stuntrider
    Posts: 2
    Any recommendations on helping pic up the torq on it. My dad owns a machine shop so motor work is no problem.
  • NZriderNZrider
    Posts: 5,153
    remove the power valve, weld up the exhaust port to lower its roof. reshape the transfer ports to arc upwards to the head to help get a better cylinder fill. raise the compression ratio up. build a custom exhaust similar to a straight pipe on a trials bike. get a smaller carb. make a reed valve made of less stiff, easier opening material. rejet and tune to suit. all this will probably nearly yeild you the low RPM torque of a 4 stroke.

    still wont perform as well as a 125 trials bike or 250f.

    my point is that your entire engine is designed and engineered around high RPM power and to undo all that careful work is stupid, and a waste of resources.

    get the engine that does what you need.
    *********************
    Winning is 90% rider and only 5% bike, the rest is luck
  • markyrocks
    Posts: 1,351
    Maybe you should try just riding the bike an get used to how it feels an how it delivers power. Any 125 2t would like involuntarily lift the front wheel with ease in the power band (if it mechanicaly sound and tuned right) . That huge rear sprocket ...... I'd b concerned with flipping over backwards. Shit my yz80 wheelies on command with stock gearing.
  • daggitdaggit
    Posts: 9,524
    Or just buy a 4 stroke.
    Never Too Old
  • Stevemite
    Posts: 5
    Its a 125 so straight geared downed you really aren't dynamic the engine. 125s are engine going to be snappy top end machines, unless you do several intellectual engine mods.
    http://www.siamvisit.com/
  • davidcullen90
    Posts: 34
    Yeah, a CR125 is a race bike, all the power is in the mid range and top end. if you want to get more bottom end, I'd put a flywheel weight on it. The heavier the weight, the more bottom end power it gets. http://www.steahlyoffroad.com/flywheel-weight.html?cat=19   Heres a website for some flywheels. They are mainly put on 2 strokes for woods riding, but it definitely improves the bottom end power!
  • gearman
    Posts: 121

    Assuming the motor is fresh with good compression, an RM 125 can easily lift the front wheel. You probably just need to practice doing wheelies,  rev it up more, yank on the bars, and sit back further than you are use to.

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