Low power and strong smell of fuel.

Discussion in 'The Workshop' started by Wez Powell, Jun 13, 2017.

  1. Wez Powell

    Wez Powell New Member

    Messages:
    9
    Hi, wondering if anyone could give any advice regarding my girlfriend's piaggio zip 2t 50cc air cooled.

    Around a year ago she noticed that her scooter was losing power and struggling to make it up hills. When she took it to the mechanic they compression tested the engine and found that the compression was very low so they derestricted it and adjusted the throttle so that it was at full throttle earlier whilst turning the stalk. They said at this point it could go around 40mph and 30 up hills.

    A year later the scooter has not been driven since and she decided to just sell it for a low price and inform the buyer however the exhaust was quite badly rusted. So I changed the exhaust for her before she sold it to make it more presentable. There was an additional pipe coming from the exhaust besides the one to the cylinder which the new one didnt have. I read online that it was some sort of air recirculation pipe and that you could just leave it so that's what I did.

    Went to test drive the bike and it won't go above 5mph and stinks of fuel. I thought that the new exhaust may have messed the air fuel mixture up so tried to tune it using the two screws (I'm guessing one it air fuel mix and one is the choke). No luck.

    I usually work on cars and I don't ready know where to start. Could this be anything to do with the new exhaust or is it likely the engine has just flat worn out?

    I also noticed that the throttle has a lot of flat spots when you rev it it just stops and drops rpm.

    How would I go about diagnosing this issue. Any help would be greatly appreciated
     
  2. Stevep

    Stevep Well-Known Member

    Messages:
    5,895
    If it's been stood for a year, have you put fresh fuel in?
    It's possible that the inside of the carb has varnished and will need stripping and cleaning.
    The larger of the 2 screws is the idle speed, the smaller one is air/fuel mixture.
    Turn the smaller one all the way in, then 2 turns out. That should set the air/fuel mix near enough for now.
    Idle speed, use your ears for that.
    Is the air filter clean?
    What exhaust did you buy? Sports or standard? Photo please.
    If it's a sports exhaust you will need to up-jet the carb a little to compensate for the exhaust gases getting out quicker.
    Do a compression test, it needs to be 90psi or above.
     
  3. Wez Powell

    Wez Powell New Member

    Messages:
    9
    Hi, thanks for the reply I have put new fuel in but didn't drain out the old stuff as it was fairly low. The air filter should be clean as it was serviced when at the mechanic. As far as I'm aware it is just a standard exhaust I have attached a picture. I will perform a compression test and let you know the results. Much appreciated.
     

    Attached Files:

  4. Wez Powell

    Wez Powell New Member

    Messages:
    9
    Think we can conclude it needs a new cylinder and piston then....
     

    Attached Files:

  5. CGC

    CGC Active Member

    Messages:
    238
    Rides:
    Piaggio Liberty 50
    depends on the mileage, possibly just a new piston and rings. the only way it would need a new cylinder would be if the one you have is severely scored, again depending on mileage
     
  6. CGC

    CGC Active Member

    Messages:
    238
    Rides:
    Piaggio Liberty 50
    the extra pipe on the old exhaust is an air catchment pipe, it was a way of restricting the compression of the exhaust port. just had a quick search and wanted to post a link but can't. the scooter will run better with the new pipe. let us know how you get on.
     
    Last edited: Jun 21, 2017
  7. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    pop that tester back in, hold throttle wide open , kick it over with ignition off , it takes a lotta kicks to build up full pressure, you stop kickstarting when the needle does not move any more.

    once you have pressure in the cylinder you wanna leave it for around 10 mins ( leak out test) if the pressure stays where it was its not bad , if the pressure falls you have leaking ring seals , if it fails to build any pressure at all the rings could have been destroyed or the piston could be holed
     
  8. Wez Powell

    Wez Powell New Member

    Messages:
    9
    I did the compression test as described above and kickstarted it until the needle stopped moving and that was the max pressure it could generate. I've ordered a new cylinder set for it as it was only cheap so I thought I'd replace the whole lot. How many ft/lbs should I torque the head on with?

    Thanks for all the replies much appreciated
     
  9. Wez Powell

    Wez Powell New Member

    Messages:
    9
    Also it was leaking down within about 30 seconds of doing it
     
  10. CGC

    CGC Active Member

    Messages:
    238
    Rides:
    Piaggio Liberty 50
    probably best to get the whole top end, dont forget to get a new top end gasket kit as well.
     
  11. Merlin

    Merlin Old School Biker

    Messages:
    2,305
    Rides:
    2007 TKR WRC 50
    While you are changing the barrel, I'd advise you to change the crankcase seals. They are a known weak point on Piaggio engines, especially the one behind the oil pump.
     
    CGC likes this.
  12. Wez Powell

    Wez Powell New Member

    Messages:
    9
    I'm a little confused at the moment. I conpleted the work on the bike today only to find that the spark plug no longer works so I'll have to wait till tomorrow to know if its worked. The thing thats confusing me though is that the old cylinder had no head gasket or o ring. Nothing. As far as I'm aware it has never been taken apart since it was new. Surely its supposed to have one?
     
  13. CGC

    CGC Active Member

    Messages:
    238
    Rides:
    Piaggio Liberty 50
    yeah it does need them. just did a search for you and there are top end kits for sale with a base gasket and cylinder head gasket. do you know which model yours is ? Any two stroke needs a seal between the cylinder and crank so the flow of fuel/air mix draws in and goes to the compression chamber, the head gasket same purpose as four strokes.
     
  14. Wez Powell

    Wez Powell New Member

    Messages:
    9
    Thanks for the reply. I got all new gaskets as part of the kit i bought so it has one now. I'm just confused because my girlfriend bought it new and its never had any work done that would involve removing the cylinder head.
     
  15. Wez Powell

    Wez Powell New Member

    Messages:
    9
    Could this be the cause of the compression issues? It's had problems ever since it was last serviced. I'm starting to think maybe the mechanic that did it could have removed it to create issues to make himself some more work. My girlfriend doesn't look like the sort that would know anything about mechanics
     
  16. CGC

    CGC Active Member

    Messages:
    238
    Rides:
    Piaggio Liberty 50
    it might be, was the piston and rings in a decent state ? the mechanic might have even forgot to put it back on

    hope you find the cause of the no spark issue
     
  17. Wez Powell

    Wez Powell New Member

    Messages:
    9
    Would he take the head off to do a service though? Piston was fairly worn but didn't look that bad. Was fairly loose in the cylinder though compared to the new one so hopeing it was piston rings that had gone. Didn't manage to start it despite trying for a while but when I checked the plug there was no spark. Then I tested the coil and it was putting out a strong 12 volts so the plug has failed at some point whilst I was working on it bizzarely
     
  18. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    one mo ill ream the ft/lb torque readinsg from my manual

    hi-per2 zip motors 50cc,
    cylinder head nuts 10 to 11 nm
    crank case bolts 12 to 13 nm
    alternator rotor nut 40 to 44 nm

    hope that helps sorry its not in ft/lbs but theres a few conversion tables out there to convert the nm reading for you
     
  19. CGC

    CGC Active Member

    Messages:
    238
    Rides:
    Piaggio Liberty 50
    just by the way you said he derestricted it and done compression tests, means they could have done anything at all. also some engines produce a higher compression ratio with a thinner head gasket. so they might gave tried running without one. My advice would be to put it back to original as best as possible anyway, as the crankshaft will not be under any excessive pressure its not designed for.

    as for the no spark I remember I had a bike with a bad suppressor cap and it took me a while to track the problem as it sometimes worked and sometimes didn't. hope yours is as simple a problem as that. if it started before it will start again, lol.

    just installed a new piston and rings in my scooter this week, it took about five kicks and about 20 turns on the electric start until I got the right mix into the cylinder, then it started first turn every time.

    let me know how you go. I expect you know how to run in the piston and rings once its started.
    what is the year and mileage on the scooter. my AP says top end service at 10000 miles.
    also says decarbon head and cylinder every six months.
     

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