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  1. #1
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    1980s 3hp Briggs help. Looking for a clutch!

    Hello everyone.

    Im looking for some advice on fitting a clutch to my 3hp. I got this from a lpcal person and it was fitted with an alcon water pump.

    Ive removed the pump to take a look at the output shaft. Its 2inches long, is part threaded and has no keyway.

    Im confident enough to cut my own keyway using my dremel, however i just really want a bit of advice as to what centrifugal clutch i need to get.

    Ive included a few pictures for you to take a look at. Sat next to one of my 2hp briggs motors for comparison.

    Cheers

    Joe

    IMG_20170418_084901.jpg
    IMG_20170418_085020.jpg
    25ur1j7.jpg
    2w1s1vk.jpg

  2. #2
    manchester1's Avatar
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    "CLONANZA CLAN"

  3. #3
    Senior Member jackeo21's Avatar
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    Looks like you scored on that 3HP! By the looks, it has the ball bearing crankshaft (much longer life over regular bushings). The motors with the ball bearing crankshafts also generally came with a cast iron cylinder sleeve, which as you may already know provide a much longer lifespan over the traditional aluminium bore. Score!

    I've been in your situation multiple times before. I generally solve my problem by finding a new crankshaft (often difficult in New Zealand!) or locating a different engine. That 2HP engine looks to be in great shape, and would take a 5/8" centrifugal clutch, as would the 3HP, but as you have noted it would take some modification to work!

    My advice would be to locate a clutch that uses two "grub screws" to mount instead of a key-way. Those crankshafts are very difficult to work with! Someone who has overcome this problem may chip in and give you some advice.

    Good luck!
    -Jack

  4. #4
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    Thanks for the reply buddy. Im fairly new working woth briggs motors, after deciding to build a classic minibike not some time ago. Would there be any performance advantage to my motor having a ball bearing crankshaft and cast cylinder sleeve, or is it just a reliabilty advantage?

    Im going to get hold of a 5/8 clutch from my local parts place, however the ones they stock do not have any set screws. Ive learned also that attatching a clutch with just set screws risks slippage on the output shaft. Ive decided to attempt my own keyway, obviuosly a mill would be great! But im going to use what tools i have avalible. Worst case scenario, i need a new crank wich i might have had to replace anyway. Otherwise i. Saving myself lots of time and money.

    I will post progress reports as soon as i start work on it.

  5. #5
    Phil1958's Avatar
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    Quote Originally Posted by Slideaway View Post
    Thanks for the reply buddy. Im fairly new working woth briggs motors, after deciding to build a classic minibike not some time ago. Would there be any performance advantage to my motor having a ball bearing crankshaft and cast cylinder sleeve, or is it just a reliabilty advantage?

    Im going to get hold of a 5/8 clutch from my local parts place, however the ones they stock do not have any set screws. Ive learned also that attatching a clutch with just set screws risks slippage on the output shaft. Ive decided to attempt my own keyway, obviuosly a mill would be great! But im going to use what tools i have avalible. Worst case scenario, i need a new crank wich i might have had to replace anyway. Otherwise i. Saving myself lots of time and money.

    I will post progress reports as soon as i start work on it.

    instead of cutting a keyway how about if you drill a hole under one of the
    set screw holes and run screw into the shaft? just a thought!
    i minibike.

  6. #6
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    I did think about it phil. Like i said though i am finding it difficult to find a 5/8 clutch with set screws in this country. Any ideas where i can find one?

  7. #7
    Senior Member lawn-boy biker's Avatar
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    ... Ive decided to attempt my own keyway...
    I've done it myself several times. Takes much time and patience to get it right.
    manually produced keyway.jpg

  8. #8
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    Right here is the plan provided that i cannot locate a clutch with set screws... Ill use the dremel with a cutoff wheel to get the line depth, then use a small grinding stone to take the shape and finish off with a file. Thanks for sharing lawn-boy

  9. #9
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    Buy a crank shaft

 

 

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