why is it so gutless?

Discussion in 'The Workshop' started by paul weston, Jul 27, 2020.

  1. paul weston

    paul weston New Member

    Messages:
    5
    I'm after suggestions.........
    I've been "volunteered" to sort a friend's son's Baotian. Initially it wouldn't start, but that is now sorted (electrical fault on the starter circuit). However, it is utterly gutless with a top speed of about 15mph on the flat. I take with a pinch of salt that it should "do 50 at least", but I'd expect 30 - even with a lump like me sitting on it!

    So far I've...
    Checked out fuel system, plenty of petrol getting to carb.
    Removed, cleaned and checked carb - nothing obviously wrong there.
    Removed air filter in case it was restricting it - no change
    Removed exhaust and checked that there were no restrictions, blocked silencer etc.
    Replaced the variator - the old one was completely knackered, briefly I hoped I'd sorted it - but no improvement.
    Checked valve clearances - according to manual
    Checked compression - about 100psi, not wonderful but should be enough.
    Tyre pressures are good.
    Front brake does appear to drag slightly but I don't think it is enough to stop it - I also removed the caliper and tried it without a front brake and it made no difference. I did replace the pads, and at the same time dismantled and cleaned the wheel cylinder.

    I'm out of ideas. I'm beginning to dislike it! It starts instantly, seems to rev OK (though never having owned one I'm not sure how "revvy" it should be) but is completely lacking in any grunt at all. I don't expect stunning performance but my velosolex can almost out perform it!
    Can anyone offer any suggestions before I return it- or consign it to the local scrap man. I hate to be beaten.
     
  2. Stevep

    Stevep Well-Known Member

    Messages:
    5,635
    Has it still got all it's original parts on it?
    original exhaust, carb, air filter etc?

    If it has an aftermarket exhaust fitted, the carb will need re-jetting to suit, however it could still be restricted through the cdi.
    Have you changed the belt?
    If you get it started, then carefully remove the belt cover, rev it up and check if the belt is going fully up on the front variator and fully down on the clutch.
     
  3. MARSH

    MARSH Whooooo!

    Messages:
    2,985
    Rides:
    Piaggio Typhoon
    Auto choke staying on ? Diaphram in carb top perished or not fitted right ?
     
  4. paul weston

    paul weston New Member

    Messages:
    5
    I checked the variator is doing its thing (and changed the belt). As far as I know (according to the owner) it is completely original and has no mods. I've not investigated the CDI (until I looked it up I didn't even know what it stood for - what is wrong with a magneto I ask!).
    I just took it for another test run (at 15mph) and it doesn't rev under load as when on the stand. If it were an old car (my area of knowledge) I'd be inclined to say the valve or ignition timing is out. Can't be valve timing (what a horrible little timing chain, I've got bigger on my bicycle) but I guess it could be ignition slipped somehow. I've been working on the assumption (from the owner) that it was running fine before the electric start packed up and he stopped riding it so I've been concentrating on things that could have failed when standing (blocked carb, fuel lines exhaust etc.). I might be able to put a dwell meter on it and get a feel for the ignition - I'm not sure if my dwell meter works on a single cylinder.
    Any other suggestions gratefully received.
    I'll have another look at the carb, but I did take it off to clean it and it looked OK and undisturbed.
     
  5. Stevep

    Stevep Well-Known Member

    Messages:
    5,635
    Na, your dwell meter won't work on this

    Where about in the world are you based?

    I'm guessing that this is a four stroke scooter? Some Baotians are 2 stroke......
    Timing wise, there is a timing mark on the flywheel and the cam, the usual both should be in line with the piston at TDC.
    Valve clearances could be too tight on the exhaust valves, but that usually makes them hard to start as well, plus a slight lock-up feel when trying to start it.
    I was thinking about something else as well but just got sidetracked by mother on the phone.................I'll be back.................

    Ah, yes........you can check the timing with a strobe on the 4 strokes, i'm guessing as an old skool spanner you have one of those hanging in the shed somewhere, unused for donkey's years, like mine. Check to see if it's advancing.
    If not then the cdi is shot, as the cdi controls the ignition advance. You can only do the static timing, nothing else.
     
  6. paul weston

    paul weston New Member

    Messages:
    5
     
  7. paul weston

    paul weston New Member

    Messages:
    5
    You're right, lots of old tools in the shed - actually the strobe was used only a couple of weeks ago so easy to hand. The result is.....
    open the throttle and as the revs start to pick up the ignition immediately advances by about 9 deg - but then as the revs increase further there is no corresponding advance in the ignition. 9 deg doesn't seem nearly enough to me (the sort of engines I have have a full advance of about 48 deg (oh for the return of the manual advance/retard lever). The handbook I have doesn't tell me what full advance should be, do you know?, but I'm sure it shouldn't stop advancing before the engine is properly revving.

    You may have put your finger on the problem. I guess I'm going to have to replace the CDI unit (unless you tell me I'm barking up the wrong tree). I'm a bit loathe to throw money at this thing as it isn't mine but they don't seem to be very expensive and it would be satisfying to get it running properly. I'll have to go and see where they've hidden it!
     
    Last edited: Jul 29, 2020
  8. Stevep

    Stevep Well-Known Member

    Messages:
    5,635
    Before you go buying anything, let us know what model of Baotian it is please.
    There might be a wire that goes into the engine casing, clutch side, that is actually the speed limiter wire to the cdi.
     
  9. paul weston

    paul weston New Member

    Messages:
    5
    There is a label on the body that says E4-4, does that mean anything? The owner repainted it, so any emblems on the sides etc have been painted over. I can't see any obvious wire going into the engine casing
     
  10. MARSH

    MARSH Whooooo!

    Messages:
    2,985
    Rides:
    Piaggio Typhoon
    Might be worth checking clutch, make sure it not got a broken spring or it's worn out, instead of the pulley halfs twisting apart they just move out but don't twist.
     
  11. Nubsey

    Nubsey Member

    Messages:
    84
    Rides:
    Honda sky 50.
    Did you ever find out what was wrong. I have a similar problem
     

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