Benelli 750 Sei back on the road

Saturday afternoon I took the Benelli Sei for a road test for about 20 minutes.

It ran well without any problems mechanically, however, electrical system didn’t cope well with a poor battery.  Looks like the battery is failing and needs replacement after 18 months of little use and not being trickle charged continuously.

Number 2 cylinder smoke settled right down by the end of the run which is great news.

Now I just need to find a service station that has an air hose that will actually fit the valve on the wheel – after trying 5 service stations on the run none of them will fit.

5 Replies to “Benelli 750 Sei back on the road”

  1. martin
    just been given a 750 sei that has not run for twenty years but has been garaged , have you any tips

    1. Hi AJ132

      Given a 750 Sei? Lucky you.

      Be prepared to spend $$$ on the bike, they are not cheap to buy parts for and I would think specialist repair places will charge a bit to work on them purely because they are so exotic. When riding the machine they have an amazing sound.

      There is nothing about them you need to be concerned about if you have owned older bikes before expect it has at least 2 more pistons than any of your other bikes. If you can work on it yourself you will save a fortune – parts for the bikes are expensive so if yours is complete you are most of the way there. If it is a restoration project missing many parts it will be an expensive project.

      Like any other motorbike that has not been started for that long I would undertake the following:-
      Change brake fluid – its likely the seals on the master cylinder and calipers have gone hard and will leak but you will soon see for your self when you bleed the brakes when replacing the fluid.
      Replace the oil in the engine as well as the oil filter – you can use one for a Honda 400/4 (CB400f) from the 1970’s, they should be the same.
      Remove carbs, dismantle, clean, reassemble
      Remove tank (you will do it when you remove the carbs any way), drain and clean inside – check for rust.
      Replace fuel line, its likely the old lines have gone hard and will crack.
      Replace battery – the old one will be shot.
      Replace spark plugs – you will need the spark plug socket spanner that fits these engine, the plugs a smaller than normal and the plugs are deeply recessed so find yourself a plug spanner.
      Inflate tyres.

      At first, turn over engine with kick started only with the kill switch in effect (or is that affect?) then try turning over with starter motor still with kill switch preventing ignition. Continue to crank till the oil pressure light goes off then disable kill switch to allow ignition, pull the choke on and see if it fires. Be careful with these engines, the choke makes the engine start with immediate high revs so be ready to reduce choke so engine doesn’t rev overly high.

      Best of luck.

  2. Hi, where can I get a spanner for the spark plugs, was all set to remove and oil the combustion chambrt as it has not been fired for a decade but .. this was a gift adn i do not want to cause any damage.. carb are seized, as well as the engine but I am told ran before hibernation daniel

    1. Hello Daniel.
      Plug spanner – good question. I recon the plugs are the same as a honda 400/4 (strange that – in fact most of the engine is the same) so you could try one of those to start with.

      I’m not sure where my plug spanner originated, it’s of the pressed metal tube variety. It seems to have been put on a lathe and machined so that the diameter of the hex drive is smaller to allow it to fit down inside the spark plug holes.

      With regards to your engine. Take no short cuts these engines are expensive to get parts for, if you try and start it after freeing what ever is seized you are likely to have a larger parts bill as you are just going to thrash out the engine. If its seized now the fact that it ran before it was put into storage counts for nothing. Pull it apart and rebuild now before starting replace the bits that are knackered.

      If you pull it apart, getting it back together is a little trickier but take notes and good luck.

  3. thank you, I used a stock spanner from a honda 360 single, mid seventies vintage, got lucky as my neighbor has that bike. lubed up the inner compression chamber ..sitting as I type. I was going to try and rock it back and forth in gear and see if I can coax it free.. has any one out there done this with success. this bike only has 6000 muiles and has not been running for ten odd years. Previous owner RIP died two years ago at age 75 At least bike was always in heated garage thanks daniel

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