PGO Bigmax / Hot 50 problems - lack of power

Discussion in 'The Workshop' started by AdrianD, Sep 1, 2010.

  1. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    My PGO stared plotting against me a couple months ago. Whenever hitting a pothole or braking hard it started to run very bad. Didn't rev, even downhill, all out of the sudden and getting progressively worse. Turned out the variator was shot. New variator and my lack of power was fixed.
    Now I'm back to similar lack of power. Some times, no matter what I do, it maxes out at 40 km/h. Other times, it slowly passes 40 and up to 55-60 it goes normal. Before this lack of power I could easily go up to 65-70 km/h. I checked the variator, it's in perfect condition. Air / fuel ratio is perfect by the looks of the spark plug.
    After a ride around town I get oil drops on the rear tire.

    Please help with some suggestions on what I can check to get to the bottom of things. I'm baffled by the problem :(
    Thanks in advance.
     
  2. grantmc3

    grantmc3 Member

    Messages:
    409
    Rides:
    piaggio nrg mc3
    could it be your drive belt or maybe your new variator has the rong waits in hope this helps
     
  3. capri dave

    capri dave Active Member

    Messages:
    5,076
    The oil spots on the rear tyre sound worrying, you really need to find where they are coming from :glare:

    a common scenario is the rear axle bearing gets very worn, allows excessive sideways movement of the back wheel, which does the seal in on the out put shaft of the gearbox, then your gearbox slowly starts emptying all over your rear wheel, drip by drip :whistle:

    put your bike on its side stand and grab the back wheel....does it feel loose??

    other than that the only other oil is the 2 stroke oil....either way oil on your rear tyre isnt an ideal situation on a scooter :glare:
     
  4. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    Cheers guys.
    The weights are ok, after changing the variator I tested several weights and all was good for 500kms. Drive belt looks fine.

    Bearing and seal are fine, the oil is on the muffler, so it's coming from the muffler.
    Here's a picture of the drips :

    [​IMG]


    Today it ran bad again, until going slightly downhill...passed 40 km/h and bam, goes excellent. Stopped at a junction and ran bad again.
    Carburetor problems ? Or drivetrain problems ?
     
  5. capri dave

    capri dave Active Member

    Messages:
    5,076
    if it revs low ish on the flat and struggles up hills a bit, but flys going down hill, thats the classic sign the rollers are too heavy....

    and yes it looks as if the oil is coming out the pipe, 2 strokes are oil burners, so you often get some unburnt oil coming out the pipe....looks like your pipe could do with a decoke and re-baffling too, by the amount of build up on your tail pipe...
     
  6. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    I'll give the lighter weights a go, even though it worked fine with them a couple houndred km's ago.

    Can't the baffles be cleaned or burned if I cut open the pipe in the largest section ?
    Decoke ? From what I can find it's the same as cleaning the baffles ?

    Thanks for the tips so far :)
     
  7. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    Haven't updated as I only now had time to test the lighter rollers. They helped a tiny bit with acceleration and worsened the "top" speed. Instead of going 40km/h it goes 30-35. With the heavier rollers it sometimes goes up to 50-55 and the engine sounds normal at that speed and sometimes it won't go faster than 30. Except for the fact that after not riding it 2 days, the first 100m it runs excellent, no other behavior is consistent. Even when going downhill, it doesn't run right all the times. Very annoying not to see a pattern in how it runs...

    I'll try cleaning the carb (again) and a new fuel filter. Any other ideas ?
     
  8. xplicit vehicle

    xplicit vehicle Member

    Messages:
    268
    Rides:
    PGO Big Max 50
    what was the problem then?

    sounds like a dirty air filter to me
     
  9. nathan93

    nathan93 Moderator Staff Member

    Messages:
    760
    Rides:
    Gilera Ice
    dont think you will get a reply he hasnt been on since november
     
  10. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    I'm back with a possible ending for my problem :)

    Air filter didn't change one thing.
    Turns out my reed valves were at fault. The valves were slightly out of shape and didn't seal right. Apparently fixed with some scavenged valves from another reed block but I was stumped to hit a bump yesterday and all previous symptoms manifested. Quite funny to ride nicely and suddenly hear the engine change tonality and lose power.

    I'm going to take it apart tomorrow, to check both the variator and the reed block. It also has a problem with the fuel pump, it will get replaced asap.

    BIG thanks to http://www.scootershack.co.uk/gener...g-parts-list-tribute-to-pgo-owners-t7533.html for the parts list, it will definitely help in case I need a new reed block.
     
  11. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    Fuel pump replaced.
    The reed valves have an extremely small opening at the top.
    Checked the variator again, everything is cool. Started the engine and ran it without the belt and variator, still ran bad so that eliminates the transmission as a problem.

    Very dark spark plug, which is weird, since after the reed valve fix a couple months ago it always looked perfect.

    However, I have found that my carburetor still leaks through the air filter, which is bad. I tried playing with the fuel level, reached a point where the needle valve would not allow petrol into the bowl and the engine ran excellent with the fuel which was in the bowl. Basically it runs very rich, no matter how I adjust the mixture.

    So far I'm putting my money on the float needle valve. That's the only thing which could cause it to run so rich and all of the sudden after I hit a bump. This probably means a new carb.
     
  12. tErr0

    tErr0 Administrator Staff Member

    Messages:
    5,816
    You sure it isn't a problem with your fuel tap?
     
  13. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    You mean the fuel pump which is on the tank ?
    New one, behaves the same. As long as there is fuel in the lines + filter it runs bad. With some fuel in the bowl it runs perfect.
     
  14. narato92

    narato92 Member

    Messages:
    46
    Rides:
    Aprilia SR 125 99"
    For me it sounds like bad settings of float in Carb. But i just guest, for me it's most reasonable.
     
  15. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    That's what I thought first. After a few miles I inspected the spark plug and it looks ok, so running rich is out of the question. That leaves the reed valves.
     
  16. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    Final conclusion:
    Stuck piston rings.

    Solution, considering the wear and tear of the cylinder and the poor quality of pistons I can find locally (30% heavier, what the?): new cylinder kit, keeping it at 50cc.

    Now, I've narrowed it to two options, Airsal T6 and Polini 1660093. The Airsal is an alloy cylinder, while Polini is cast iron. Airsal is cheaper but with Polini I have options in case I will need to re-bore the cylinder further down the road. What are your thoughts ? Which one should I go for ?
     
  17. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    Polini kit installed and I think I'm going to set the bike on fire.
    Just as I turn it on it smokes like crazy, I suspected it's just extra oil I used for lubrication of the cylinder kit components but even after idling for 15 minutes the smoke didn't clear.
    It runs rich as hell again. Tried adjusting the air/fuel screw, nothing. Only improvement (in the smoke level) is when I remove the air/fuel screw completely. I've also raised the needle as per instructions in the guide on the main page and no change. Tried all float levels and nothing improves. It seems like whatever I do it runs worse and worse.

    Just in case, I looked at the reed valves and they seal ok. And I tried it again with the belt and variator removed, no change.

    In a nutshell it has zero power, pops when holding the revs constant and smokes like crazy.
    I'm totally at loss with this thing. Help ? :cry:
     
  18. AdrianD

    AdrianD New Member

    Messages:
    13
    Rides:
    PGO Big Max 50
    :yahoo: :yahoo: :yahoo:
    The beast is fixed.
    Turned out to be a very clogged exhaust. This is how the exhaust looked inside:
    [​IMG]

    Welded back, first time using the MIG on such a thin material:
    [​IMG]
     

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