Newbie with minarelli problems

Discussion in 'The Workshop' started by Miller35, Oct 8, 2017.

  1. Miller35

    Miller35 New Member

    Messages:
    4
    Hi all,
    I'm new to here and to scooters (years of experience on mx bikes so I know my smokers well)
    I'm in desperate need of help with a 50cc minarelli horizontal fault I have on an Aprilia area 51 I've got my son (not the best I know but it was dirt cheap)
    It runs fine on the stand and on the road providing you don't hold it at Wot for too long.
    If you do it just bogs out after about half a mile sometimes with a little backfire but restarts straight away.
    I was told it had a 70 kit on it but the barrells marked 50cc, it also has a de restricted Leo Vince tt pipe.
    Still on a 12mm carb (45 pilot and 95 main) I've ordered a 17.5mm and jets to swap out.
    Looks like standard Reed block and reeds which are in good order.
    Plug seems to be a nice colour.
    Things I've changed so far:
    Coil-swapped for a higher voltage version
    Plug
    Fuel pump-binned the vacuum pump for a 12v one as it was starving at high rpm

    It definitely feels like fuel starvation when riding, but I'm starting to to think it's too lean on the main despite a 95 being quite big..
    It's not affected by engine rpm as sometimes it can do it at lower rpm's ie head wind and WOT.

    Any help is appreciated as I'm now banging my head and he's doing my head in now he's done his cbt.
     
  2. scubabiker

    scubabiker NITROJUNKIE

    Messages:
    7,321
    Sounds lean to me too, even with that jet. Go bigger and see.
    Hows the airfilter?
     
  3. Miller35

    Miller35 New Member

    Messages:
    4
    On standard air filter but ive cleaned it out. Think I may wait for the 17.5 carb and start from the beginning. Cheers
     
    scubabiker likes this.
  4. Sam phantom

    Sam phantom Active Member

    Messages:
    874
    The minarreli engine is a very good 50cc unit I'd class it as one of the best.. I think your main jet is way to big for your 12mm carb should be around 68 if your running standard air box

    Edit: have you considered running premix it may be a oil starvation issue ? If the bikes getting on abit
     
    Last edited: Oct 8, 2017
  5. Sam phantom

    Sam phantom Active Member

    Messages:
    874
    And got any pictures love the Area 51 unusual bike
     
    RLH5 likes this.
  6. Miller35

    Miller35 New Member

    Messages:
    4
    I'm just going to start over on the bigger carb at the weekend. Don't think it's too rich as it's not fouling the plug. The main problem is I don't know what has actually been done other than what I can see.
    Does anyone know of a 70 barrel that is casted with 50 on it?
    I've had 62 out of it before its died off and it was still accelerating slowly but it was still pulling. That seems a bit fast for a standard 50.
     
  7. Sam phantom

    Sam phantom Active Member

    Messages:
    874
    I have almost the same set up as your bike if yours is a 50cc.. I have standard air box leo vince pipe and I also have the 12mm gertner carb mine is a minarreli engine also and I'm running no where near a 95 jet it's around 68/70 runs perfect does about 55mph max! 95 jet is much to big unless your running a 70cc
     
  8. Miller35

    Miller35 New Member

    Messages:
    4
    That's what I though with the jets at first but looking at the plug it's not flooding or anything and the backfire suggests it's lean.
    What's your theory on oil starvation causing it?
    I thought it would just do main or little end if oil, not just bog out and refire straight away.
    Just trying to find as many other possibilities / things to check as I can before the weekend
     
  9. Sam phantom

    Sam phantom Active Member

    Messages:
    874
    Well you say it's fine unless you hold the throttle open for to long, if the pumps getting weak as it's an old bike ?then as it gets hotter (max rpm)the amount of oil being fed isn't enough to keep it oiled/cool hence the bogging (heat seizure) then on tick over and mid range it runs fine as you say.plus if it is a 70cc which I I think it is with a 95jet then it won't be getting enough oil from the standard pump any way, def worth checking while your dwn there with carb
     
    Last edited: Oct 10, 2017
    Miller35 likes this.

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