Why erratic throttle on 48cc?

Discussion in '2-Stroke Engines' started by geebt48cc, Mar 15, 2010.

  1. geebt48cc

    geebt48cc Member

    Everything runs great, but it doesn't want to always take consistent throttle? Some days on same road it will run 30 +, but others, only about 25 max? New in line filter,25:1 ratio, I've run total in kit 1 1/2 gallons.....

    TY :whistling:

  2. motorpsycho

    motorpsycho Active Member

    what kind of weather are you having right now?
    beleive it or not, the temp. of the air can drastically affect how these engines run. on cold days it may want to run lean, on warmer days, it may want to run rich (air/fuel mixture that is).
  3. geebt48cc

    geebt48cc Member

    Yes, I understand , but it seems to do this if it's in the 40's or in the upper 70's? Mmmmm, appreciate..............It runs good if I'm moving the choke lever every so often.
  4. motorpsycho

    motorpsycho Active Member

    If you have to move the choke or if it runs better when you close the choke, it may be running too lean. have you taken the top off the carb to see where your needle clip is set?
    you may have to move the clip down, which will raise the needle in the needlejet further and richen the mixture up by letting more fuel into the engine.
    i have found that (on my engine anyway) i had to play with the needle jet setting once i got the engine broken in for it to run right.
  5. geebt48cc

    geebt48cc Member

    Yes, I'll try that....(I did this once before, but it was when it was very cold outside)..........It's on second from top now. I'll drop it to the third slot and see if that helps. TY
  6. happycheapskate

    happycheapskate Active Member

    I agree. I have about 400mi on my Grubee 48 now. It seems very temperamental about moisture content changes moreso than temperature changes.

    If you make short trips, try starting by just priming 2x and pedaling, instead of choking. This seems to help me get more consistent performance out of it.

    As far as speed changes, mine goes about 32 on flat ground with no wind, and bogs down a little to about 27 with a headwind, maybe 25 with a real stiff headwind. On wet, foggy days, it seems to run "richer", more prone to make the "4stroke" sound at half throttle. I don't worry about it too much. I don't want to move that stinking clip for every weather change. Just make sure its getting enough fuel and oil. Tune it for the weather you get the most.
  7. geebt48cc

    geebt48cc Member

    Yes, I've got the Grubee 48 also. I'll try that. See, it's on a 26" MTB. lol, I'm a bigger guy (6' 7", 250lbs.) I've got pictures in pic gallery, about page 4. What ratio would you go with now that I've got about 3 tanks used? (Been using 25:1)

    I can run about 28-30 on flat.............No wind!~
  8. happycheapskate

    happycheapskate Active Member

    I use 32:1 every tank. I use Either Walmart 2cycle boat oil, or Home Depot Power Care.
    I plan to use that as long as I have the motor, as I use it for most of my commuting and some fun riding on days off. Some run 40:1 but I wouldn't go with less oil than that. So far the muffler has stayed very clean and no fouled plugs.
    I am using a 26"x1.75 beach cruiser. Good luck! These things are so much fun.
  9. geebt48cc

    geebt48cc Member

    Ok, I'm going to go with the 32:1 as well. I've just got alittle of last tank of 25:1 left. So, it's about 72 outside today, and I just wanted to see, so on a flat, it topped out around 32mph. (Not bad for a 48cc with 252lbs rider...........lol)
  10. happycheapskate

    happycheapskate Active Member

    I think I may have found an answer


    This is a high quality fuel petcock replacement from Sick bike parts.

    The reviewer says the original part is restrictive (from a subjective test, true, blowing through one off the bike), but claims the new one has aleviated the erratic throttle problem on his bike.

    I'm going to try it because I like the part anyway, and I thought about removing the stock in tank filter anyway. (if it clogs, I have a bunch of fuel to siphon out. If my Autozone inline filter clogs, I can pinch it off and put another filter on there in a minute. )

    PS, if it is erratic at full speed, this could be from a cycle of cooling and slight overheating of the engine, or from the bowl float in the carb cycling, if the float valve is sticking.)

    Try oiling your motor chain heavily and see also if that helps. Can't hurt anything.
    Last edited: Mar 18, 2010