Ariel Arrow / TZR250 crankshaft conversion

  1. FZR750 Member

    Messages:
    16
    UK Leeds
    I am rebuilding my Ariel Arrow crankshaft and would like to use TZR 250 con rods and big ends , from a crank that I have acquired.
    I will be fabricating a press, but what tonnage is required to separate/ assemble cranks?
    Some machining will be required to fit the TZR crankpins into the Arrow crank wheels, just wondered if anyone on here has attempted this?
     
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  2. Rannsachair

    Rannsachair Forum Supporter

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    1,076
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    Lochgilphead, Argyll, Scotland
    ronan and gordon stephenson like this.
  3. FZR750 Member

    Messages:
    16
    UK Leeds
  4. ronan

    ronan Forum Supporter

    Messages:
    8,964
    dublin
    I think most old british singles had tapered crankpins, i know BSA b series singles and goldies had them. Whereas modern singles have straight sided pins which are better. I would think a 50 ton press would be the one.
     
  5. Seadog

    Seadog Forum Supporter

    Messages:
    4,526
    Location:
    NE London - UK
    AJS/Matchless had parallel pins. Not sure about the Norton singles though, never rebuilt one of those.
     
    Last edited: Aug 25, 2017
  6. FZR750 Member

    Messages:
    16
    UK Leeds
    Crank pins locate in the flywheel with a parallel 18mm diameter, on the Ariel arrow.No nuts. Press fit.
     
  7. Seadog

    Seadog Forum Supporter

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    4,526
    Location:
    NE London - UK
    I'm pretty sure that all stroker cranks are pressed together. I'm fairly certain that a 10-ton press would do it without any trouble. I used to rebuild Bantam, Tiger Cub and BSA unit cranks using a fly press, I can't remember the size though but possible a No. 5.
     
  8. LC Racer Member

    Messages:
    38
    Kent
    I rebuild Tzr250 cranks for our race bikes. I take it the crank is the 1KT/2MA type. The crank pins are square not tapered.
    The rod eyes have a habit of wearing oval so careful insection is needed, any pitting or signs of ovality then bin them.
    Use the flat cage big end bearings, actually a RD500/TZ part, much stronger then the standard castled bearing which breaks along the bearing ridge. I'm assuming you will be using the TZR little end bearings, if so the genuine small ends are far better than anything else on the market, some of the pattern ones are shocking

    Components are available from PJME or Grampian motors, who sell the Mitika range mainly

    I have 20T press, about 8-10 tonne is normal to get them apart, but I've had the odd stubborn one
     
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  9. Gwil Member

    Messages:
    524
    Location:
    Portugal
    I'd love to see updates on your Arrow. I had two at the end of the 60's. One had reputedly been tuned by Herman Meier, had padded crankcases/flywheels, a big carb and, of course, expansion chambers. It had been radically ported I discovered when I put new rings in it, and I kid you not it was significantly quicker than my pal's CB72., if a tad less sophisticated....

    I put a CB72 front wheel in it with the excellent tls brake. It handled very well in what was then my limited experience! The power came in with a bang, unlike the much more civilised standard one I used for commuting to school. I loved it. Miss it still- my dream stroker would be the Kwak 500 I saw in Motorcycle City for sale in about 1970, huge tank, humpy seat, rearsets and spannies. Four hundred quid, no way could I afford it, then or now sadly.
     
  10. LC Racer Member

    Messages:
    38
    Kent
    This is one I did recently, if you look in the big end slots you can see the flatter cages to the big end bearings, The main bearings are Koyo brand. I've never had one fail yet. Worth the money.
    The crankpins are integral with the inner crank webs. If you need a crankshaft with the pins seperate then the only option would be the RD250 Aircooled crank. Rare and physically bigger though. The center pin is seperate, with the ab seal and mains pressed on centrally. There is no inner seal apart from the center lab seal

    299629_10200185425938338_1165950787_n.jpg
     
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