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256 vs 447? Here we go...

Discussion in 'The Garage' started by Freak, Apr 8, 2010.

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  1. Freak

    Freak XS650 Enthusiast

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    Ok guys I know ive read this before about the 256 going to pieces in a short order at high rpm's and etc, but i happen to have a 72-256 motor that im wanting to rebuild, just piston and ring for now. I guess I just want to know if im wasting my time and money on this motor and should I just go out and find a 447? Any input would be great. Thanks guys.:shrug:
     
  2. xsjohn

    xsjohn 8-1 lover

    Think they built the 447 so they could rev the wobbly crank even more...:yikes:....I would like to built a 256 motor for torque someday......probably never will with all the 447 parts I have.....:shrug:

    xsjohn
     
  3. From what I read on the net, 1972 don't have a 256 but a 306 engine. I don't know the difference , maybe they share a lot of internal parts.
     
  4. inxs

    inxs xx

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    - the main difference between the 256 and 306 cranks was the addition of the starter gear on the crank for the e-start...there were slight differences in the crank flywheel and os pistons...the XS1-XS1F cranks were unified to 256-11400-01
     
  5. Thanks inxs for this info.
     
  6. cruza

    cruza XS650 Enthusiast

    freak isthe 256 the eariler version of the 447, cause if it is they are the longer conrodded version ,which makes them more effeficient power wise
     
  7. Freak

    Freak XS650 Enthusiast

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    Yes earlier than the 447 and harder to find parts and normaly more expensive. There are many pros and cons. For instance the race guys liked these motors back in the day but they most likey were not using the same rods and pistons just a lot more beefed up. I dont plan on racing it though.
     
  8. wurlzy

    wurlzy XS650 Member

    Hi guys, this might be obvious to some but i'm new to the XS world.
    Could someone please explain to me what the reference means when describing the different engines......256, 447, 533.
    And where/how does one find out what exactly is in the bike?

    Thanks in advance,

    Steve
     
  9. inxs

    inxs xx

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    - 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
     
  10. JAGUARGOD

    JAGUARGOD XS650 Addict

    WOW! Thanks for asking that Steve...I was feeling really dumb....well I am actually.
    Just didnt want to be the ONE....LOL.
     
  11. 270YAM

    270YAM XS650 Addict

    Another difference with the 533 crank: the big ends are 2mm wider than 256/447.
    From memory the 256/447 rods are 20 mm wide and 533 is 22 mm wide.
     
  12. gggGary

    gggGary On the road of life I'm a speed bump. XS650.com Supporter Top Contributor

    Will 306 crank, rods, pistons etc fit into a 256 block? I have a stuck 256 showing 34,000 miles and a donor low mile 306 if the parts would fit. What about cylinder sleeves, do they interchange throughout the years?
     
  13. 270YAM

    270YAM XS650 Addict

    Any crank will should fit in any set of cases, and all the sleeves and barells should be interchangable. The early barrels had a 4 bolt cam chain tensioner, where the later ones have a 6 bolt tensioner.

    The only combination I would not recommend is a 256/306/447 crank in 533 cases. Althought they will physically fit, I am told that the 533 cases do not have the oil spray holes at the front to lubricate the big ends. :thumbsup:
     
  14. builder

    builder XS650 Addict

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    so if I am reading this right, the 306 motor can use the 477 crank, con rod and piston combination but what about the bores and head?
     
  15. ReycleBill

    ReycleBill Part Time Tyrannicide XS650.com Supporter

  16. builder

    builder XS650 Addict

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  17. gggGary

    gggGary On the road of life I'm a speed bump. XS650.com Supporter Top Contributor

    " subscribed? "

    It's an option up on the top, under the thread tools menu. Unlike a reply that just gets you the next post and nothing more til you visit the thread again if you subscribe there, you get ALL replies to the thread even if you don't look at it again. Very handy for tech threads of interest or if you are following one of the excellent build threads around here. Or by typing at least 8 letters in reply you will see the next message posted to the thread and can renew by clicking on the thread link in the email.
     
  18. grizld1

    grizld1 Grumpy old man Top Contributor

    270YAM, you are misinformed. The same wristpin diameter--22 mm.-- was used in 256 and 306 long rod engines, along with a hotter camshaft and 17/34 crankshaft/camshaft sprocket combination. The 447 short rod engine uses a 20 mm. wristpin, milder camshaft, and 18/36 sprocket combination.

    The only significant differences between the 256 and 306 motors, apart from the absence/presence of the electric foot and one of the tranny bearing seats, are in the top end. In 256 cylinders there was a bridge in the cam chain tunnel that forced splitting the cam chain for disassembly, and the head gasket sealing surface pattern on the cylinder top and head was narrower than the pattern on the 306 (which was retained for the 447).
     
  19. Rabbidmk1

    Rabbidmk1 XS650 Enthusiast

    hi guys,

    I need to chime in here for a bit of advice. I came across a 750 kit with a parts bike that I acquired but have come to realize it is a mismatch of parts. I have 79mm pistons with 22mm wrist pins and a regrind cam stamped 447 with a 36 tooth sprocket. Having 2 engines to use for parts, am i correct in thinking I can build this in a 256 engine and swap the 34 tooth sprocket from my stock 256 cam to this larger regrind?
     

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