Bonelli Sei Rebuild in the U.S
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Thread: Bonelli Sei Rebuild in the U.S

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    Senior Member
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    Steve Siggins
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    Bonelli Sei Rebuild in the U.S

    Anyone know of somebody who has done any Sei engine rebuilds in the U.S?
    I don't really have the facilities or knowledge of 4 strokes to do this and to be honest find the concept a bit daunting.....
    Last edited by Orlando6; 01-09-2018 at 07:00 AM.

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    Senior Member
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    Quote Originally Posted by Orlando6 View Post
    Anyone know of somebody who has done any Sei engine rebuilds in the U.S?
    I don't really have the facilities or knowledge of 4 strokes to do this and to be honest find the concept a bit daunting.....
    Guess its down to me then....not looking forward to this one!!

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    Senior Member R Powell's Avatar
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    Richard Powell
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    Hi Benellis we’re hand assembled and are quite straight forward to dismantle using the manual.
    you might need some service tools to dismantle it. These are available from Germany
    good luck

    Richard
    The Benelliman
    1981 Benelli Sei 900
    1989 Benelli Sei 900
    1976 Benelli 125 Enduro
    1981 Benelli 250 2c
    1976 Benelli 250 Quattro
    1992 Ducati. 907 ie

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    Bonelli Sei Engine rebuild

    Quote Originally Posted by R Powell View Post
    Hi Benellis we’re hand assembled and are quite straight forward to dismantle using the manual.
    you might need some service tools to dismantle it. These are available from Germany
    good luck

    Richard
    Dont fancy the idea of trying to get 6 pistons and rings into the cylinders there must be some special tool for that.
    Will most probably try to get her running after servicing, compression test and valve adjustment etc and see where we are from there.
    Thanks for the reply....

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    Senior Member black nails's Avatar
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    I must admit, I have yet to tackle a sei, but, you are only putting two pistons at a time into the cylinders, just get someone to support the weight of the head while you tease them in.
    It is the strip down of old bike engines that is the pain, if it has been untouched for a long time, just dunk the lot in diesel fuel for a week or so before you start, and just take your time, don't try to rush it, and a hot air gun is your friend.

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    Member Cosmo's Avatar
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    Steve,

    Don't be too daunted.
    The engine really is quite simple excepting there are six reciprocating elements to deal with.
    The main issues will be corrosion & rubbish fastenings etc as noted above. Replacement screws will certainly be needed for the rebuild and some of the sizes although metric have a shallow allen head, so are unusual.

    For the barrels, there are only a few special tools for the engine as a whole (see gearbox shaft puller) although you could use piston ring compressors as shown in the manual, I have never needed them. Two pistons at a time keeping it all level seems to work on the fours or the sixes, no different really, it is just the weight and size of the barrel to deal with and being extremely careful with the oil scraper rings.
    You just need to take your time and ensure you fully support the barrel. It helps to have a couple of "mechanically sympathetic" helpers keeping an eye on where everything is - I suggest a promise beer AFTER the job is done!

    Good luck.

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    Senior Member DenH's Avatar
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    dave kitson in decator indiana,was a dealer for years and a wealth of info.
    when i was young i was very indecisive,now im older im not so sure.

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    Senior Member black nails's Avatar
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    "Will most probably try to get her running after servicing, compression test and valve adjustment etc and see where we are from there."

    If it is your shiny engine, if it turns freely, then I would strip and service the carbs, drop the sump to clean out any sludge, change the filter, squirt a bit of oil into the bores, fit new spark plugs, refurb the ignition system, fill with oil, then see if it starts and go from there.
    There may not be much wear inside, any light corrosion on valve seats etc will soon clean its self up. after running for a couple of hours off and on over a few days, change the oil again.
    If it's the dirty engine, you will want to get it turning first. put good penetrating fluid into the bores and give it time to do its thing, put a rod down the spark plug hole and give the tops of the pistons a sharp tap, if that frees them, happy days, if not, put the whole thing into a bath of penetrating fluid, diesel fuel is good, and leave it for a week or so, somewhere warm preferably, then start stripping, very carefully, and take your time.

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    Hi
    when I don't feel up to puting the barrels down over the pistons on an engine I split the cases, put the pistons with conrods in the bores then mount each rod in turn onto the crank with the engine upside down. Is there any reason you can't do this with a sohc Benelli?

  11. #10
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    Bonelli Sei Engine

    Yes its my shiny engine, although not shiny enough.
    With my Kawasaki rebuilds I like to send everything off to be vapor blasted so the engine looks brand new.
    So I'll just polish and paint this complete engine as best I can before putting it in the frame.
    I,ll think I'll take black nails advise and just keep her together as the valves top end looks brand new.
    Found some paperwork that came with this engine/frame saying it had been stripped and inspected so its worth a try.
    Thanks for the advice its appreciated.

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