Yamaha SR250 Classic

Discussion in 'Old's Cool' started by oc_nightmare, Jan 18, 2010.

  1. oc_nightmare

    oc_nightmare Been here awhile

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    Hi there folks

    I just bought a SR250 classic for commuting and doing nice trips on the summer and i'm absolutly loving it because it feels so light (I come from a XTZ750 Super Tenere:D)

    Here it is:
    [​IMG]

    I was wondering if there are more SR250 owners here and as soon as I get a new bike, my mind starts to work real hard to do modifications to enhance the bike, mainly the performance from the engine.
    I've already ordered a megaphone muffler and i was thinking on what can i do to gain a little bit more torque on the low and middle range? What engines fit this frame with minor modifications? Would the XT350 one fit? As it is a very oversquare engine i think it is not recommended to go up in the bore, is it? I would be very happy with 350cc SOHC and this bike and this weight but what engine to put there?

    If the SR500 was sold here in Portugal or if it wasnt so expensive to bring one here, it would be so much easier :cry


    Im sorry for my english :(:
    greetings from Portugal
    #1
    pilot9545 likes this.
  2. Chobro

    Chobro spinning the wheel

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    Cafe it! Or just ride it.

    I dig it
    #2
  3. oc_nightmare

    oc_nightmare Been here awhile

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    the only thing im thinking on doing about that is to drop the front forks and adding clip-ons :evil

    what about the engine, any ideas?
    #3
  4. oc_nightmare

    oc_nightmare Been here awhile

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    no ideas? :cry
    #4
  5. BIG ED XT FAN

    BIG ED XT FAN Long timer

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    We did not get that sr 250 here in the USA. The bike that came here had a "pizza" box on the back end. No disk on the front end.
    A new muffler and some clip-ons for a start. And new paint! Thump-On!!:evil:evil:evil:evil:evil
    #5
  6. JWhitmore44

    JWhitmore44 pistolero

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    You will probably need to search on XT250 to see what people have done to increase performance on those. You might want to check in the thumper section. I think the XT225 was replaced with an XT250 this year. If you have plenty of top end you can go with a bigger rear sprocket, 3 or 4 teeth bigger.

    Cool looking bike.
    #6
  7. Inane Cathode

    Inane Cathode Cheated Anion

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    It's also just a 250, can't expect starship performance from it.
    #7
  8. eric123

    eric123 Gott Mit Uns

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    Personally I would just leave it alone and ride it as is. I would look for another bike to mod and keep this one a runner...

    Many times I have bought a bike and thought to myself, "I will just change this one small part and be up and running in a day." Three years later the bike is still in parts scattered around the shop...Never tear apart a running, fully functional bike when it is your only runner...You will quickly look back and think, "Too bad I didn't get to ride this year either, maybe next year"
    #8
  9. Mista Vern

    Mista Vern Knows all - tells some.

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    Wise words that apply to all kinds of "I can make this just a little bit better" projects. :deal
    #9
  10. oc_nightmare

    oc_nightmare Been here awhile

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    Here are two little updates on the SR :evil
    - New Shorty Reverse cone muffler, sounds awesome now, have to rejet it now though
    [​IMG]

    Had to replace the front sprocket, the teeth were all bent... rear one and chain are fine.
    [​IMG]
    [​IMG]
    [​IMG]

    Thanks for the comments guys :wink:
    #10
  11. eric123

    eric123 Gott Mit Uns

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    That is a great looking bike. I would love to own one. Looks like the previous owned reversed the front sprocket at one point?
    #11
  12. Putts

    Putts Gettin' there.

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    Gotta pitch in with the "leave it alone and ride it" croud. That's a cool looking little bike just as is.

    :wave
    #12
  13. brucifer

    brucifer Long timer

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    #13
  14. Zecatfish

    Zecatfish XTique Rider

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    There is another thread on TT about a YZ465/TT250 Franken bike.

    In Short, heres the breakdown.
    Yamaha YFM350 84mm piston and sleeve, the engine case has to be enlarge to fit the larger cylinder into it.
    The wrist pin has to be reamed out to 20mm, from 19mm.
    He also used a WebCam (regrind stock cams) for more mid and top end.
    Copper head gasket, .21" thick.
    Makes a 310cc Engine.

    I'm going with the same type specs, except its going to be an XT250, I'm going to put it in a YZ490 chassis.
    #14
  15. oc_nightmare

    oc_nightmare Been here awhile

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    zecatfish and brucifer, i read the thread on YZ465/TT250 frankenbike and it was quite an awesome build :thumb

    did he use the stock XT250 head? Aren't the valves too small for the larger piston?

    for 2 more milimeters he could use the XT350 piston and sleeve, why didn't he?

    Cheers
    #15
  16. Zecatfish

    Zecatfish XTique Rider

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    The Big Bear quad is a two valve engine. I think thats the reason for that, plus it has the same piston height from the wrist pin to crown.
    He used the stock head.

    Theres another fellow working on if an XT500 87mm will work.
    Not sure there is enough material to bore out the cylinder that large. Might break through to the cooling fins. Then there is the issue. Would there be enough material at the cylinder studs to retain reliability, it would make 340cc.

    There is one other fellow on TT that has and XT250 bored/stroked to 430cc. :evil
    #16
  17. oc_nightmare

    oc_nightmare Been here awhile

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    jesus :eek1

    could you get me more links and info? it would be nice to get that kind of info on this topic, in case of someone has the same engines as this ones :wink:

    one of my fears is that the XT and SR250 have such oversquare engines, if one is going to increase the bore so much, i have no idea what can happen... mainly because of the piston weight and speed.

    any idea on HP and torque gain for the 310, 340 and 430cc preparations?
    #17
  18. bill pierce

    bill pierce I don't wana pickle

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    I would replace the chain as well. A stretched chain is what causes wear like that. In fact, if you change the chain before it stretches too far sprockets last much longer.

    The reason the rear doesn't look so bad yet is because the chain has more wrap around the sprocket.
    #18
  19. oc_nightmare

    oc_nightmare Been here awhile

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    i dunno bill, the chain looks quite alright of wear and i tensioned it when in swapped the sprocket... i will take a closer look at it though :nod
    #19
  20. Zecatfish

    Zecatfish XTique Rider

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    I know very little on the 430 stroker.
    http://www.thumpertalk.com/forum/showpost.php?p=7557967&postcount=34
    And the Powroll he mentioned.
    http://www.powroll.com/
    I can't help more than that.
    Your on your own from there. :D

    you could build a little sleeper that would surprise a few folks.

    #20