75O SEI does not start. Help!.
Benelli Motorcycle Forum - Benelli Bike Discussions - Powered by vBulletin
Page 1 of 4 1234 LastLast
Results 1 to 10 of 34

Thread: 75O SEI does not start. Help!.

  1. #1
    Senior Member tucandugu's Avatar
    Member #
    7370
    Join Date
    Sep 2008
    Location
    Barcelona
    Posts
    452

    75O SEI does not start. Help!.

    Hi. Help please. I am desperate with my 750 Sei.

    Just replaced the old breakers by a Sache electronic ignition, did the test, all the plugs firing.
    After some attempts engine started, running apparently right (no strange sounds, smooth, etc.).
    But after 20 seconds, engine stopped.
    After this, had been impossible to start up again. Some times seems the engine is near to start up, others not.
    I am totally confused now. Note that most of the elements are new: spark plugs, carburetors cleaned, air filter, fuel pipes.
    I replaced the old breakers thinking that this was the problem, because before of this, the motorcycle did the same symptoms (first attempts started up but after a while, stopped).

    Any idea?.

    Thanks in advance.

    Carles.
    Benelli TNT 1130 Sport EVO 2008 - Benelli 750 Sei 1977 - Moto Guzzi 65cc 1957 - Vespa Primavera 125 1977

  2. #2
    Junior Member
    Member #
    9960
    Join Date
    Feb 2010
    Location
    Brisbane, Australia
    Posts
    21
    Hard to diagnose on the net but, if you're getting good spark, maybe starving for fuel. Have you cleaned the fuel taps?
    76 Benelli Sei, 76 Guzzi Lemans, 79 Guzzi Lemans, 79 Kawasaki z650, 98 BMW F650, 08 Suzuki DL650

  3. #3
    Senior Member tucandugu's Avatar
    Member #
    7370
    Join Date
    Sep 2008
    Location
    Barcelona
    Posts
    452
    Thanks Doc59!. The fuel taps are also new, but I will check the fuel flow. Head exhaust of cylinder number 5 seemed to be cold, while the rest warmed up. The engine does not stops suddenly but slowing down the revs before the definitive stop. This makes me think, like you, that is something related with the fuel; nevertheless the cold exhaust confuses me.
    Benelli TNT 1130 Sport EVO 2008 - Benelli 750 Sei 1977 - Moto Guzzi 65cc 1957 - Vespa Primavera 125 1977

  4. Remove Advertisements
    BenelliForum.com
    Advertisements
     

  5. #4
    Junior Member
    Member #
    9960
    Join Date
    Feb 2010
    Location
    Brisbane, Australia
    Posts
    21
    Carles, I'm no expert, my 750 is still a museum piece with a sheet over it but I'll throw ideas at you if they help at all.

    Cylinder 5 staying cold could be a different problem as well, maybe try swapping spark plugs and see if the fault follows, if it was electrical or 1 carb, I would expect 2 cylinders to stay cold.

    Messy way to check your fuel flow, pull the float bowls off one at a time and turn your fuel on, fuel should pour out until you lift the float gently to seat the needle.

    Basically, since it ran alright for a while and now won't start at all, you're back to basics: - Fuel, Spark, Air in the right order.

    Thinking aloud here, since you had the problem before you changed the ignition system, have you checked compression and valve clearances???

    Good luck and let us know what you find.
    76 Benelli Sei, 76 Guzzi Lemans, 79 Guzzi Lemans, 79 Kawasaki z650, 98 BMW F650, 08 Suzuki DL650

  6. #5
    Junior Member
    Member #
    12545
    Join Date
    Nov 2011
    Posts
    20
    If you haven't tried yet run hose from fuel taps into a jar to see if fuel flows for a long period without slowing. May be fuel cap vent problem? Or try with float bowls off to see if flow is good.

    Wouldn't hurt to connect volt meter to battery or coil to be sure volts don't drop while its running.

    I hope its something simple.

  7. #6
    Senior Member tucandugu's Avatar
    Member #
    7370
    Join Date
    Sep 2008
    Location
    Barcelona
    Posts
    452
    Many thanks for your comments Doc59 & Edgefinder. After two days I am recovering from the frustration and may be tomorrow I try to check all this suggestions. May be I am too optimistic but still I think that must be a nonsense. Hope so...
    Benelli TNT 1130 Sport EVO 2008 - Benelli 750 Sei 1977 - Moto Guzzi 65cc 1957 - Vespa Primavera 125 1977

  8. #7
    Senior Member tucandugu's Avatar
    Member #
    7370
    Join Date
    Sep 2008
    Location
    Barcelona
    Posts
    452
    Hi again, guys.

    I did the continous firing test (mode 0) of the new electronic system.
    Test worked satisfactorily. I paid special attention to cylinder nr. 5, that suspected is not working properly and it gives spark clearly.

    Then I tried to start up the engine, without choke, and it started up quite easely. No mechanical sounds, but needed to maintain the accelerator to avoid it stop. After a while, I leave the accelerator and the engine has stopped immediately.
    I Touch the 6 exhaust head pipes and clearly the number 5 was totally cold while the rest was warm.

    Exhaust fumes and nr 5 plug smells clearly to unburnt fuel...

    Now is obvious that fuel is arriving and also is the spark ; then, what can cause this malfunction?. Note that the rest of cylinders seems to work perfectly as they can "hold" the engine working with "only" five cyl. May be a wrong valve clearance adjustment in this cylinder?.

    Thanks and regards.

    Carles.
    Benelli TNT 1130 Sport EVO 2008 - Benelli 750 Sei 1977 - Moto Guzzi 65cc 1957 - Vespa Primavera 125 1977

  9. #8
    Senior Member WikingTNT's Avatar
    Name
    Per Kolbjørn Almaas
    Member #
    8550
    Join Date
    Jan 2009
    Location
    Trondheim -Norway
    Posts
    1,817
    Hola Carles- wish I had some technical insight's , so I could have an excuse to pop down to your lovely place in Costa Brava and help you out. Cause here in the North it's storming,cold and pissing rain

    Hope you get your wonderful SEI in order and send regards to Jo

    Salud

    Pk
    pk

  10. #9
    Senior Member tucandugu's Avatar
    Member #
    7370
    Join Date
    Sep 2008
    Location
    Barcelona
    Posts
    452
    Hi Per!. Do a quick mechannical course for SEI´s and come here. Still nice weather, you will be welcome to visit us.
    Today I disconnected from the Benelli world for a while and took a round with my Vespa 125 trying to get inspiration to fix the conflictive SEI . As you probably read, I could start up it, but cylinder number 5 is failing. Tomorrow more tests and also some swimming on the beach to relax...
    Best wishes and regards to Maritt from both of us.
    Carles.
    Benelli TNT 1130 Sport EVO 2008 - Benelli 750 Sei 1977 - Moto Guzzi 65cc 1957 - Vespa Primavera 125 1977

  11. #10
    Senior Member dobbinuk's Avatar
    Name
    Lee Hardy
    Member #
    10139
    Join Date
    Apr 2010
    Location
    Ringwood, UK.
    Posts
    2,529
    Could it be lack of compression in no.5 Carles?

Page 1 of 4 1234 LastLast

Sponsors

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Similar Threads

  1. Hot start
    By aussie1 in forum TNT
    Replies: 9
    Last Post: 06-24-2011, 07:52 AM
  2. Bad start to the day
    By Scotland in forum The "Other" Biker Bar
    Replies: 7
    Last Post: 06-16-2010, 06:09 PM
  3. My CR won't start!
    By D'Artagnan in forum TNT
    Replies: 20
    Last Post: 05-24-2010, 09:23 AM
  4. Help - Won't start
    By andy1962 in forum Tornado Tre
    Replies: 11
    Last Post: 03-23-2010, 03:29 AM
  5. Start me up !!
    By stevet457 in forum Tornado Tre
    Replies: 22
    Last Post: 04-03-2009, 12:37 PM
Google+