Yamaha dt230 big bore kit

Discussion in '2 smokers' started by Trailhound, Jul 5, 2013.

  1. Trailhound

    Trailhound n00b

    Joined:
    Jul 3, 2013
    Oddometer:
    5
    G'day fellas I'm new here so sorry If this is in the wrong spot but I was wondering if you guys could answer a question for me We got given a Yamaha DT230 L for free and has everything on it that we need to rebuild it but the Cylinder is scratched so I was wondering if I could get a stock YZ 250 big bore kit in it

    Cheers Trailhound
    #1
  2. stainlesscycle

    stainlesscycle Long timer

    Joined:
    Jun 6, 2008
    Oddometer:
    2,330
    Location:
    morgantown, wv
    yz250 is 66.4 mm x 72.0 mm

    dt230l is 66.8 mm x 64 mm

    so that's a no. not a drop in. unless you: trench cases, change rod/crank/etc etc. etc etc etc. lotsa work.
    #2
  3. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    4,902
    Location:
    New Zealand
    The DT230 is a big bore DT200....it started life as a 125, stretching to 250 is a bit much. The DT125 is an almost identical bike, lots of parts fit the 230.
    #3
  4. Trailhound

    Trailhound n00b

    Joined:
    Jul 3, 2013
    Oddometer:
    5
    thanks for the replies fellas i was just curious because my cylinder has a few scores in it and instead of paying over $1000 for a new cylinder i thought i could bore it to a 250 but i guess ill just get it re chromed

    cheers trail hound
    #4
  5. BygDaddee

    BygDaddee Where do I get a pie

    Joined:
    Oct 26, 2012
    Oddometer:
    3,357
    Location:
    Brisbane Northside, OZ
    Check this thread out too
    http://advrider.com/forums/showthread.php?t=715716

    #5
  6. Twin-shocker

    Twin-shocker Long timer

    Joined:
    Jan 28, 2012
    Oddometer:
    1,673
    Why not see if a big bore cylinder for a Blaster will fit? If it does then I would guess cost would be a lot less than re-plating.
    #6
  7. stainlesscycle

    stainlesscycle Long timer

    Joined:
    Jun 6, 2008
    Oddometer:
    2,330
    Location:
    morgantown, wv
    plate it for $150-$200 and be done with it. if you're gonna play with porting - now is the time. basically impossible to port after nikasil is on..
    #7
  8. Twin-shocker

    Twin-shocker Long timer

    Joined:
    Jan 28, 2012
    Oddometer:
    1,673

    I get the feeling the OP is interested in a cost effective way of getting his bike running properly again, and probably not interested in "porting" which is something that costs a fair amount of money, and in almost every case makes the modified bike much more difficult to ride.
    #8
  9. stainlesscycle

    stainlesscycle Long timer

    Joined:
    Jun 6, 2008
    Oddometer:
    2,330
    Location:
    morgantown, wv
    dang, i forgot. professor twin-shocker is in the house :rofl:rofl

    replating is the most cost effective way. cheaper than any other method. he did mention big bore, so i suggested now was the time to port since a big bore is not going to happen - i assumed he wanted more power.. proper porting does not make a bike more difficult to ride. you can port for performance in any area. a big bore kit would cost more than porting/replate.
    #9
  10. joexr

    joexr Banned

    Joined:
    Jan 4, 2011
    Oddometer:
    5,022
    What kind of oil should he use?:rofl
    #10
  11. Twin-shocker

    Twin-shocker Long timer

    Joined:
    Jan 28, 2012
    Oddometer:
    1,673

    In almost every case "porting" will make bikes more difficult to ride, as in most all cases this relates purely to extending post open times, which will make peak power occur at much higher RPM, and in many cases will be less than the stock porting would provide.

    An inexpensive way of dealing with a worn cylinder, would be a cylinder kit intended for a Yamaha Blaster, but obviously the OP would need to find out whether this would fit his bike properly.
    #11
  12. dpforth

    dpforth no inline fours

    Joined:
    Oct 22, 2010
    Oddometer:
    497
    Location:
    YQQ
    I believe the Blaster was only aircooled.
    #12
  13. Twin-shocker

    Twin-shocker Long timer

    Joined:
    Jan 28, 2012
    Oddometer:
    1,673
    Dohhhhhhhhhhhhhh.................my mistake! No problem at all admitting I am completely wrong.
    #13
  14. joexr

    joexr Banned

    Joined:
    Jan 4, 2011
    Oddometer:
    5,022
    How deep are the scratches? Do you see them or can you feel them?
    #14
  15. joexr

    joexr Banned

    Joined:
    Jan 4, 2011
    Oddometer:
    5,022
    Porting does not make a bike harder to ride. The power peak may be at higher RPMs , but this is determined by the pipe as well. MUCH higher RPMs , no. More power , yes.
    #15
  16. Twin-shocker

    Twin-shocker Long timer

    Joined:
    Jan 28, 2012
    Oddometer:
    1,673
    I wonder how on earth extending the port open times, which means power is produced much higher in the rev range, helps to make a bike easier to ride?

    Proper motor set up, and paying careful attention to suspension are both things that should be looked out before spending money on "porting"!
    #16
  17. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    4,902
    Location:
    New Zealand
    The DT230 has a big hit off the bottom end; that's why it was made, the DT200 was too peaky. Because of the instant off idle power it has traction control...just an ignition retard when it detects too much wheel spin. I don't know if it really works, in slippery conditions it still wheelspins like any 2 stroke, I guess you'd have to disconnect it to find out. I thought mine was a well balanced little package powerwise.
    #17
  18. stainlesscycle

    stainlesscycle Long timer

    Joined:
    Jun 6, 2008
    Oddometer:
    2,330
    Location:
    morgantown, wv
    porting is not just changing port timing. . sure if you raise the exhaust/transfers it will change where the peak power is. improving shape of ports increases flow, and you can also widen ports, optimize the port surfaces, increase or decrease fuel charge velocity, optimize transfer flow, etc. all without changing port timing at all.

    i'm pretty sure a dt230 is not hard to ride stock. making more power at a specific rev range does not make a bike harder to ride. let's say you normally ride 125mx'ers. when you get on a stock dt230 it could be more difficult to ride, since you're used to riding on the pipe and the top of the rev range. making a bike faster/more power does not necessarily mean it's more difficult to ride. maybe more difficult to ride slow. but who wants a bike that's hard to ride fast, and easy to ride slow? oh, i know. a trials rider. the dt230 is not a trials bike. it's definitely not a race bike either. but it would be nice to know the power is available if you wanted it. for me it's MUCH harder for me to ride a bike that falls flat on it's face on the top... i'll take a peaky motor all day over a torque motor. at least i know if i hold it wot it will rev to the moon until i decide to shift, instead of short shifting the hell out of it....and if you keep them on the pipe, you're getting all the power, all the time. some 2 strokes are meant to be ridden in the screaming overrev. it's what makes a 2 stroke fun. even modern 4 strokes try their damnedest to duplicate the top end power delivery of a 2 stroke.

    i'm gonna guess there is tons of hidden power in the dt230 cylinder...it's your choice whether to optimize it or not. there is some very simple porting that can be done to most cylinders that will increase power everywhere...without making it peaky... that being said, yamaha generally has pretty good port design stock, and generally the ports are already optimized for the power delivery they assume most riders want.

    there is no doubt proper suspension setup (i'm assuming the stock dt230 suspension is kinda pitiful) will make a dt230 easier to ride faster...or slower for those who like that kind of thing.


    either way replating is the cheapest in the short and long term. unless the dt230 had a boreable liner originally - i do not know - but i doubt it - are any newer water cooled bikes made with boreable liners anymore? i believe everyone has switched to nikasil..





    .
    #18
  19. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    4,902
    Location:
    New Zealand
    Have you ever ridden a DT230 ? They make power everywhere, strong bottom end, and with stock gearing will pull over 160kph (100mph) - that's pretty damn impressive for 225cc. You'll be on a much bigger bike to get more performance than a DT230, and it's just so much fun to have this much get up and go on a small bike with all the extras it has. I'd ride one before I tweaked the porting...Yamaha has this one sorted, 2 strokes didn't get much more sophisticated than the DT230.
    #19
  20. stainlesscycle

    stainlesscycle Long timer

    Joined:
    Jun 6, 2008
    Oddometer:
    2,330
    Location:
    morgantown, wv
    i have not, they are not available in usa. as i said, yamaha usually gets port design pretty close. i never assumed it was gutless, just assumed it could be made less gutless :D - the original poster mentioned yz250 top end, which no doubt would increase the hp significantly. it seemed he wanted more hp and a new cylinder all in one fell swoop - i was just suggesting where hp gains could be made. i also assume there is a restrictor in the exhaust, or carb that could be removed for more hp - most street legal 2 strokes now have a restriction somewhere to meet government exhaust restrictions...

    that being said, top speed is primarily a function of gearing, not horsepower.. just about any bike with 20hp or more can most likely attain 100mph...as long as the power to weight ratio is reasonable..


    i don't doubt this for a second - it appears to me that it's an evolved wr200 which was a fine bike in it's own right.
    #20