Oversize Cylinders
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Thread: Oversize Cylinders

  1. #1
    Senior Member elime's Avatar
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    Oversize Cylinders

    If thinking about installing an oversized piston buy a cheap, dirty, rusty cylinder. Clean it up and let the machinist bore the rust away (or oversize hone it yourself). Keep your original cylinder and piston on the shelf in case your upgrade doesn't work out as planned.

    Case in point. Two cylinders bought off ebay. One is for an XT-200 and the other for a YFM-200. Both will work on the TW. The XT was $20, the YFM was $13.99. S&H included on both.

    As received:
    As received.jpg

    Ready for honing or boring:
    Ready for machining.jpg
    scotti158, Ken, DrTerrible and 1 others like this.
    Long live the internal combustion engine!

  2. #2
    Senior Member Fred's Avatar
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    Tony, you sure are good at finding value. The re-cycled cylinder and Wiseco piston I got from you are still running strong, saved me a pile of cash. Thanks Again!
    Ken, Dryden-Tdub and elime like this.
    2003 TW200 "Betty Boop"
    2006 TW200 "Nibbler", a.k.a. “Mr.Gizmo"
    Hidden Content All Things Considered I’ld Rather Be Motorcycling

  3. #3
    Senior Member lbxr's Avatar
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    I have been using the ttr 225 jugs and punching them out from 70mm to 71mm to use the 71mm Wiseco 10.25 C/R piston for the YFM 250...for 229cc. I like using the late model cam chain adjuster over the early style...which I have never understood. I have built 3 of the 229cc motors this way and I am very pleased with the results...very peppy off the bottom and good power everywhere compared to stock.

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  5. #4
    Senior Member Fred's Avatar
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    IBXR, could I bribe you to build me a motor?
    Pretty please with sugar on top? With a 6-speed too?
    Seeing you zip around Moab was mighty impressive.

    Now that Gerry’s Mr.Gizmo bike addresses the suspension shortcomings of the stock TW the engine shortcomings beg to be improved. The long travel Tri-Z forks and Blaster shock really soak up surprise hits from potholes and other obstacles, now just need more oomph to take advantage of greater suspension capabilities.
    Last edited by Fred; 05-21-2017 at 11:01 AM.
    Dryden-Tdub likes this.
    2003 TW200 "Betty Boop"
    2006 TW200 "Nibbler", a.k.a. “Mr.Gizmo"
    Hidden Content All Things Considered I’ld Rather Be Motorcycling

  6. #5
    Senior Member lbxr's Avatar
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    Quote Originally Posted by Fred View Post
    IBXR, could I bribe you to build me a motor?
    Pretty please with sugar on top? With a 6-speed too?
    Seeing you zip around Moab was mighty impressive.

    Now that Gerry’s Mr.Gizmo bike addresses the suspension shortcomings of the stock TW the engine shortcomings beg to be improved. The long travel Tri-Z forks and Blaster shock really soak up surprise hits from potholes and other obstacles, now just need more oomph to take advantage of greater suspension capabilities.
    Fred, thanks for the compliment....I really liked the high compression motor in Moab, It seems to help with the altitude. I would be happy to build you a motor....if you lived nearby! Problem is, if there is a problem with the motor after I build it, I would want to stand behind it and that gets difficult if there is alot of distance between us. These are super simple and reliable motors and easy to build, but I can make mistkes as well as anybody! Problems are rare but they do happen, and if you live nearby...we can fix anything that goes wrong, quickly!

    For instance I would be happy to sell this motor.... I just bolted a 70mm ttr 225 OEM piston and cylinder onto a super low mileage 87 tw200 5 speed motor, just for fun....resulting in a 214cc 5 speed, up from 196cc. The tw 200 mouth had to be opened up to accept the 70 mm jug and it seems to me the resulting opening is a bit narrow where the base gasket and jug mount to the case. So I think it is possible the jug might be able to walk around on the case and allow oil seepage there. The cylinder "landing" is at least as wide as the gasket and probably will be fine...but if I sell it to someone far away and there is a problem.....so pretty much it goes up on the shelf next to my collection of spare parts.

    Since Moab, I have been working on my suspension a bit too....I machined an aluminum bottom triple tree to see how it would work out. It turned out pretty nice and saves about 2 lbs there over the cast steel one. I used 3/4" plate and probably should have used 1", but it seems to be plenty strong. Next I plan to machine one using 1" aluminum plate to accept 36 mm forks, like the ttr 225/230 forks....Well someday....

    Bob
    Mel likes this.

  7. #6
    Senior Member Fred's Avatar
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    Understandable. I feared getting the case mouth opened up properly for the 70mm jug so didn’t pay much attention to the good engine build threads posted here in the past. Plus I am lazy.
    However after hitting a few potholes with the Tri-Z forks I realized I could go much faster before getting into an equal amount of trouble like when the stock forks hit a surprise G-out.
    For that I could use more power. As someone once said “There is no replacement for displacement"
    Every bike has a limiting factor that hopefully is not too far out of balance with the bike’s other strength and weaknesses. Stock TW lacks some suspension finesse. Fix that and then a breathed on motor can really shine. The 36mm fork conversion sounds a winner if coupled with longer swing arm and/or taller shock to balance out the rear.
    lbxr and centralwarider like this.
    2003 TW200 "Betty Boop"
    2006 TW200 "Nibbler", a.k.a. “Mr.Gizmo"
    Hidden Content All Things Considered I’ld Rather Be Motorcycling

  8. #7
    Senior Member lbxr's Avatar
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    If I use the 36mm forks, I will limit the fork travel, to about the stock travel plus an inch maybe. Same on the rear but with a aftermarket shock? I keep hoping someone will find the perfect alternate shock. I do not feel I need alot more travel, just better dampening and resistance to bottoming (especially the rear suspension). I really like the frame geometry of the stock TW and the low seat so I do not want to stray too far from stock. Or add a bunch of weight either.

    The extra power, especially the grunt off the bottom, is really nice, but going faster or riding harder is not what I am after....I am more interested in increasing the TW's capability for more technical riding or should I say ease of use in the more difficult terrain we have around here. Or in Moab!
    centralwarider likes this.

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