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Thread: XS650 build.

  1. #21

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    I guess I’m just looking for info on if this is big trouble or something minor. I know I bought a basket case and half expected stuff like this.

  2. #22

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    It's been years and I am surprised that you're not yet done with this build. Maintaining a classic bike nowadays is hard.

  3. #23

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    Not sure what's up with your case, maybe someone on here more knowledgable can help.
    You can probably find another on ebay if it turns out you need to. Since you got the whole thing apart you might as well do a big bore kit on it.
    Last edited by SaddleTramp98; 07-09-2021 at 10:01 AM.

  4. #24

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    I’ve looked around and it’s just a starter elimination job. I’ll plug it back up with a freeze plug, what I’ve seen on some forums after looking around. All the big bore kits I see are for 1974 and up. I believe mine is a 72. Not sure what the difference is. I think Heiden tuning has the big bore for early models but there around €900.

  5. #25

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    Still not sure about the repair work. It’s where the kick start shaft inserts.

  6. #26
    Senior Member

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    Join Date
    Dec 2017
    Posts
    2,588

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    All the big bore kits I see are for 1974 and up. I believe mine is a 72. Not sure what the difference is.
    256 vs 447? Here we go...
    "- the numbers are cast into the conrod
    256...136mm conrod, 22mm wrist pin, 26mm crank pin, no starter cog...306...same with a starter cog
    447...130mm rod, 20mm wrist pin, 26mm crank pin, starter cog
    533...140mm rod, 20mm wrist pin, 29mm crank pin...mostly sold in europe

    - because the bores and strokes are the same each crank type has its own pistons...the cranks can be swapped complete with their rods and pistons...there are other differences in the motors-compression ratios, clutches, cam timing, gearbox etc .."
    http://www.xs650.com/threads/256-vs-...re-we-go.1204/


    Technical Stuff

    TORQUE AND REPHASE THEORY
    XS650 CAMS
    WHICH OIL TO USE
    YAMAHA XS650 HI PERFORMANCE GEARBOX MODIFICATIONS
    880cc ENGINE BUILD
    CYLINDER BORES AND PISTON RINGS
    MODIFYING THE ADVANCE AND RETARD MECHANISM
    Click image for larger version. 

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    "(All crankcases from 72-84 are essentially identical, only XS1/B cases are different). For this build I purposely chose the roughest set in my spares stock to illustrate what can be done with a little hard work. Inspect them carefully for damage, the kick-start lug breaks, damaged threads, and very rarely cracks near the studs."
    Click image for larger version. 

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    "The 880 kit can only be used with a 533 crank. This crank was used on European only XS650 engines, it has a larger 29mm crankpin, and the connecting rods have 140mm centre. This gives a rod to stroke ratio of 1.89:1 which reduces piston side thrust loads, and subsequent wear rates. Ensure you have a 533 crank; the 447 and 256 cranks will not work with the 880 conversion. If your crank is in excellent condition it can be re-used, but if it is in any way suspect then replacement of the worn parts is recommended for long engine life, these engines are very high torque and will “spit out” any suspect parts. "

    http://www.smedspeed.co.uk/tech.html

  7. #27
    Senior Member

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    Join Date
    Apr 2013
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    9,267

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    I'd avoid throwing money at any 650cc twin since the best way to get HP without buying oddball wear parts whose replacement requires yet more oddball wear parts which may no longer be available years down the road is buy an engine that makes HP in the first place.

    Many bike builders "chase statistics" when they benefit much more from simplicity and reliability. It's also a good idea to hoard stuff like spare engines if keeping a machine and the earlier ya score them the better deal ya get as supplies dry up over time. An engine is not a marriage and if a better deal comes along there's no reason not to pounce on one needing less work.

  8. #28

    Join Date
    Jul 2021
    Posts
    10

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    Looks like an interesting project! Subbed

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