750 sei engine ?
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Thread: 750 sei engine ?

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    Senior Member black nails's Avatar
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    750 sei engine ?

    A nagging thought has been kicking around for a while, instead of chucking time and money on my much abused 500 ls engine, why not replace it with a 750 six!
    The rolling chassis is near enough the same, and mine is in quite good condition, I wouldn't even need a complete engine, the ancillaries are the same, as are the outer covers, I could even rig it with six carbs!
    What do you think? how much would an engine cost without the ancillaries? and the outer exhausts?
    or is this just a pipe dream?
    Is this allowed?
    Will I go to hell?

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    Senior Member R Powell's Avatar
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    Benelli six engines as rare as rocking horse poo!, you are right they do fit and it has been done before though . I think one of the German suppliers had some new engines in crates but it might cost more than it's worth!. I spent over a thousand euros on a barrel and six pistons for my 900 six!
    The Benelliman
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    1992 Ducati. 907 ie

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    750 engine

    there was/is a 750 sei engine for sale in Car And Classic for 1,500 euros! (its in Spain though)

    pondman

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    Senior Member black nails's Avatar
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    It looks like they are a bit steep, still, I will start looking , you never know your luck. and I really don't mind doing work on one, if the price is right.

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    Member Cosmo's Avatar
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    Quote Originally Posted by black nails View Post
    It looks like they are a bit steep, still, I will start looking , you never know your luck. and I really don't mind doing work on one, if the price is right.
    I have done it! The sei engine does indeed fit straight into a 354/500/654 frame, engine plates and all. It's very naughty, but with a bit of bracing and mods or replacements to the suspension you get a sweet looking special. Beware though, because just because it looks standard apart from paint, it is far from it. There are lots of handmade parts and problems to solve before it works like this. It does however weigh next to nothing compared with standard - less than a new Yamaha R1 fully fueled and ready to go.

    Six carbs will need a modified tank because the throttle quadrants of 2 banks of 504 carbs just foul the bottom seam of a standard 504/654 tank. Next on my "to do" list..........

    The larger heavy framed early 500 Quattros are however exactly the same as a Sei, I think even the extra 2 exhausts and brackets fit straight onto the Quattro as-is.

    See below........owned since 1983
    750 sei engine ?-img_352599149373481a.jpeg 750 sei engine ?-photo-4.jpg
    Last edited by Cosmo; 08-29-2017 at 10:18 AM.

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    Senior Member black nails's Avatar
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    That is a credit to you, I love the colour scheme, I can see many very good mods, swinging arm, rearsets,many more, brilliant.
    Is this a 750 or 900? Like I said earlier, I am a fabricator / engineer, with good access to a very good mate who is a bit of a wizard on his cnc, lathes, mill etc. so a bit of modding is no problem. The rolling chassis is in very good condition on my 500 LS but the engine is a bit dodgy, so I think the time is ripe for building a special, maybe not as radical as yours, who knows.
    I am now actively looking for an engine, I have even written to santa !! If anyone has a spare, please get in touch.

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    Member Cosmo's Avatar
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    Quote Originally Posted by black nails View Post
    That is a credit to you, I love the colour scheme, I can see many very good mods, swinging arm, rearsets,many more, brilliant.
    Is this a 750 or 900? Like I said earlier, I am a fabricator / engineer, with good access to a very good mate who is a bit of a wizard on his cnc, lathes, mill etc. so a bit of modding is no problem. The rolling chassis is in very good condition on my 500 LS but the engine is a bit dodgy, so I think the time is ripe for building a special, maybe not as radical as yours, who knows.
    I am now actively looking for an engine, I have even written to santa !! If anyone has a spare, please get in touch.
    It is a 1978 Sei electronica spec 750 engine with a sachse ignition. Built up with CB550 pistons, Ravasio wild cam and modded followers giving 820cc, so not quite a 900, but all is well tucked in and with far more ground clearance!
    Last edited by Cosmo; 08-30-2017 at 01:43 PM.

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    I have no commercial interest, blah blah blah...
    https://www.milanuncios.com/motos-cl...-236251934.htm
    Here's a 900 Sei in working order with a second 900 Sei for parts breaking. I live in Spain and happy to help with translation or phone calls if it may be of interest. PIck up a 900 dirt cheap and use the second bike to rebuild? Food for thought..

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    Senior Member black nails's Avatar
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    Thanks for keeping me in mind, but all I need is an engine, not even a full one, I have the ancillaries and side cases and contents within, on my 500LS engine.

  11. #10
    Member
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    There's a bare 750 engine block on ebay in the US, and a complete motorcycle as indicated yesterday... now to find something between those two conditions!

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