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Thread: One for Stewwie.

  1. #11
    Heh, heh...gee haven't seen that before...well no more that about 20 times!

    The SR can suffer from a couple of performance related consequences. Cylinders, little ends on con rods, the occasional crankcase even.

    One of the often experienced problems however is cylinder failure...they normally fail right where yours has. Mostly in race engines however but I have seen one or two on road bikes. Often there'll be oil everywhere.

    Cylinders consequently are more difficult to come by than most other SR parts, maybe with the exception of electrical stators...or maybe they're on a par.

    Ask around any wreckers near to you as a start or if no luck try Ito on here who's in Japan. He'll likely have more luck.

    There are a few different style mods you can do to 'strengthen' a good cylinder, especially if you plan to keep working it hard...have a look around on here or on the old Forum.

    SR
    Last edited by stewross; 06-08-2017 at 07:42 AM.
    ...'Any unnecessary items on the bike, that it doesn't really need, shouldn't be there!'. (Café racers creed). SR..

  2. #12
    Quote Originally Posted by red dragin View Post
    that's, umm, interesting!
    'Tis a mere scratch, surely it will buff out Actually, interesting is a restrained understatement More like appalling…

  3. #13
    Yes Stew, I cracked the case a month or so back and had that repaired and re-enforced on the outside and fitted a rubber bush to the rear of the head steady but I think the damage was already done.
    When I find a new cylinder I'll extend the short stud near the spark plug right down to the flange to give some support in that area, it's a long way between the studs on that left side there.
    I'll also strip the cases and have the old crack welded on the inside as well.
    This motor sure does make some torque considering the little it's had done to it.
    Surprisingly when it broke I rode home 10 miles no problem with no oil leak.

    If you hear of a cylinder for sale please let me know.

    davy
    Adding power makes you faster in the straights.... adding lightness makes you faster everywhere: Colin Chapman

    There is a quintessential elegance to riding a single cylinder machine: OCR

  4. #14
    Don't know of any cylinders sadly...a mate who races has sucked up all of the spare ones I knew of...and a set of nice cases too...which no longer exist in good condition...

    400 cylinder would do and is more easily available...cheap from Japan...Ito again.

    SR
    ...'Any unnecessary items on the bike, that it doesn't really need, shouldn't be there!'. (Café racers creed). SR..

  5. #15
    Senior Member gcrank1's Avatar
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    Since you were pleased with the performance pls document for us what made it so once inside.
    '81 Yamaha SR500 Caff Racer
    '09 Suzuki TU250X 'The Silent Red Fellow'
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    In all things maintain your uprightness lest the road reach up and smite thee

  6. #16
    Quote Originally Posted by stewross View Post
    Don't know of any cylinders sadly...a mate who races has sucked up all of the spare ones I knew of...and a set of nice cases too...which no longer exist in good condition...

    400 cylinder would do and is more easily available...cheap from Japan...Ito again.

    SR
    Stew, are the 400 barrels a straight fit and can they be bored to 90mm like my 500 is?

    davy
    Adding power makes you faster in the straights.... adding lightness makes you faster everywhere: Colin Chapman

    There is a quintessential elegance to riding a single cylinder machine: OCR

  7. #17
    Quote Originally Posted by gcrank1 View Post
    Since you were pleased with the performance pls document for us what made it so once inside.
    The bottom end is stock, the cylinder is bored with a 90mm piston for 535cc with a 323 Tighe cam, a properly jetted 38mm Mikuni and a full bore straight thru stainless exhaust from Motolana.
    No air filter, I run a custom made velocity stack 98m at the end with 2mm stainless gauze to stop rocks and it's exactly 11 inches from the end to the inlet valve center which seems to produce a lot of torque.
    Jetting is 260 main, 35 pilot, #2 air jet, P5 needle jet 6F9/4 needle and a 2.0 slide. Power delivery is instant, no flat spots, takes a bit of getting used to on first crack of the tap in spite of the 17/40 gearing. The 130kg all up weight is part of that too I suppose.
    The twist grip is fast action, less than a 1/4 turn closed to wide open.
    Ignition is stock with one of Rex's cdi boxes and I have only 5 lighting coils out of the original 14 on the stator to reduce power losses and it still makes enough wattage to run a 60 watt headlamp and charge the Lipo4 battery at 14.2 volts on the run and 14.4 with the headlamp off and the R/R doing full duty.
    Ign is run a few degrees retarded to help defeat detonation and I run an Aussie made octane booster which also helps as well with that as well as giving a much better burn and flame travel in the cylinder and a bit more grunt.
    That's about it really.
    I believe it's just a really good combination of carburation, cam, motor size and exhaust that works so well as a package.
    I did run 17/41 gearing for a while but it was to hard on the rear tyre and it felt like a mad thing so that's why I went to the 17/40 setup to calm it down a bit. It's a lot easier to ride now.

    davy
    Adding power makes you faster in the straights.... adding lightness makes you faster everywhere: Colin Chapman

    There is a quintessential elegance to riding a single cylinder machine: OCR

  8. #18
    I found a second hand cylinder at a wrecker in Cairns so that part of it it good.
    I have some questions:

    1/. Where can I source new piston rings for the 90mm JE piston in this motor?
    Kedo don't have them nor do Motolana.

    2/. How much trouble would it be to press out the 90mm sleeve from the broken cylinder and fit it to the secondhand replacement I bought? or would it
    be simpler to just have the new one bored to 90mm?

    davy
    Last edited by Old Cafe Racer; 06-18-2017 at 07:22 PM.
    Adding power makes you faster in the straights.... adding lightness makes you faster everywhere: Colin Chapman

    There is a quintessential elegance to riding a single cylinder machine: OCR

  9. #19
    You can heat the cylinders and press the liners out but that can occasionally be a little hit and miss in some ways with how well (tight)? they fit into the other cylinders.

    Better to re-bore the new one to suit...rings should be available from J&E in the US.

    I'll do some checking.

    SR
    ...'Any unnecessary items on the bike, that it doesn't really need, shouldn't be there!'. (Café racers creed). SR..

  10. #20
    Last edited by stewross; 06-18-2017 at 08:17 PM.
    ...'Any unnecessary items on the bike, that it doesn't really need, shouldn't be there!'. (Café racers creed). SR..

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