1967/1969 Bonnie Rebuild Desert Sled Project - Any Advice

Discussion in 'Vintage Classics' started by Sundance, Sep 15, 2021.

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  1. capt

    capt Elite Member

    May 8, 2016
    3,052
    750
    western Australia
    The internal cable/protrusion length is the critical length , too much and you can't apply the brakes , you need to make a spacer to take up the slack or a new cable with the correct protrusion length
     
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  2. darkman

    darkman Crème de la Crème

    Oct 26, 2015
    7,588
    1,000
    Southcoast of the UK Earth
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  3. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
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  4. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    Regarding oils and break in procedures, I’d appreciate any guidance on the proper way to break in my rebuilt engine. It is a 1967 Bonneville motor with a 750 kit. New barrel, pistons, cams, tappets, pushrods, all bearings and bushings (including cam bushings). Any suggestions on how to break it in most effectively? Thanks.
     
  5. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    1,113
    243
    appalachia usa
    #365 speedrattle, Aug 6, 2022
    Last edited: Aug 6, 2022

    i set it up for break-in on assembly. generous assembly lube on rod ends, crank, cams, and tappets. no synthetic oil. i use brad penn 30w break in oil.

    from here i depart from conventional wisdom. i assemble the jugs dry-- no oil on cylinder walls, zero.

    one drop on front and rear piston skirts, zero oil on the rings. some people use more oil on cylinders, like a wipe with an oily rag, then wiped as clean as youcan with clean paper towels.

    whatever you do, when you start it, keep the rpms up above 2000 for a couple of minutes while you verify oil return.

    what i do then is take it out and ride it. up and down through the gears. no lugging, no racing around at high rpm, but load the motor to force the rings out--firm acceleration, firm deceleration, open throttle, closed tbrottle. . . . no extensive idling. keep the rpms up so the oil is splashing around.

    do this for half an hour or more. i have an airstrip where i break in motors, and that works well.

    after that, take it home, adjust the timing and idle, torque the head, adjust the valves.

    ride it firmly but not crazily for a few days and youre done. i routinely do this to a fresh race motor, and after several hours of this, its ready for 8000 rpm WFO, even with pretty close piston tolerances.

    other people will have othwr suggestions. there is no one right way. you can get the same results with different techniques.
     
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  6. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    Thanks Speedrattle. I kept the jugs dry and used a good amount of lube elsewhere. Also used brad penn 30 break in oil. I went out once, right away after starting, for about 20 miles, up and down the gears as suggested. Let it cool, tightened the bolts and nuts. I did this a second time also, for another 20 miles.

    I need to adjust the carbs a bit as it seems to be running rich as I get some backfires when off the throttle. I guess it is also time to check the valves now. When you talk about adjusting the timing - I assume you are using a timing light? If so I need to get one. Thanks.
     
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  7. learningtofly

    learningtofly He’s not the Messiah, he’s a very naughty boy!
    Subscriber

    Sep 25, 2018
    2,031
    1,000
    Hertfordshire
    Fascinating thread for a non-techie like me, I must say. Fantastic support from some very knowledgable members here, but kudos to the OP too - it's a big project.
     
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  8. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    There is no way I could have started this project, much less get it to completion, without this forum - and another forum too. The manner in which members freely share their expertise and passion points to the good in humanity - and has been an unexpected benefit in this journey!
     
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  9. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    1,113
    243
    appalachia usa
    yes, use a strobe light for final timing. the dactory just static-timed the motor and sent it out. you can do better. i recommend a dial back to zero light, so you can get actual numbers fir advance and so on

    i learn stuff on these forums all the time. during thev80s and 90s there was nowhere to leafn. the internet has changed all that by facilitating communication and access to old information.

    just be aware tberes BS out there too
     
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  10. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    I’m just now getting around to my T120R build again. I am going to check my valve clearances after having run the engine for about 90 miles. I see in the Clymer manual that the valve clearances for the 650 are supposed to be 0.002” (0.05mm) intake and 0.004” (0.10mm) exhaust. Then for the 750 it is supposed to be 0.008” (0.20mm) intake and 0.006” (0.15mm) exhaust. So my bike was a 650 and now has a 750 kit on it. I’m assuming that since it was originally a 650 I should use the clearances as for the 650 shown in the book? Thanks for any comments.
     
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  11. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    1,113
    243
    appalachia usa
    nope

    use the 650 figures unless youve gone to an aftermarket cam.

    even then the clearances are somewhat approximate. you can modify tbem a bit to change your valve timing.
     
  12. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    1,113
    243
    appalachia usa
    nope

    use the 650 figures unless youve gone to an aftermarket cam.in that case do what the cam perso n says to do.

    even then the clearances are somewhat approximate. you can modify tbem a bit to change your valve timing.
     
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