Spark plug dirty / hesitation on brand new motor

Discussion in 'Motorized Bicycle Trouble Shooting' started by XFITcruizer, Apr 26, 2012.

  1. XFITcruizer

    XFITcruizer New Member

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    I just got my bike kit 2 days ago. I hope im not doing permanent damage to my bike, but i started noticing a few things.

    -engine is hesitant.. I can be cruising along (maybe 15-20mph) and the engine is running rough, then all the sudden it smoothes out and I immediately feel it accelerating and has more power; but that is short lived and quickly starts running rough again and wont let me go past 20mph until it smooths back out

    -I noticed this black oil/fluid around the spark plug on cylinder head. Not much but enough to make me look closer. I took it out (see pic below) and you would think it had 10,000 miles rather than less than 10! It looks like the ratio is way too rich. I am at 7,200 ft above sea level, so I adjusted the carb jet to be leaner but havent really got to test it out (bad storm outside).

    -There is also black oil/fluid very slowly dripping out the tailpipe when running. Mind you, the gas/oil mix is at about 20:1 for break in, and is light sky blue in color (synthetic 2 stroke oil) and is coming out black-as-night out the tailpipe.

    Again, I am a newbie but this does not seem right. The spark plugs that were left in past 80,000 miles on my wifes car looked better than this one does after 10 miles. Basically, what I want to know is did I mess up? I am assuming I will need a new spark plug, I just hope I dont need much else! Thanks for your help!
     

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  2. 2door

    2door Moderator
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    You need to give your engine a little time before you start trying to diagnose problems. Start by reducing the amount of oil you're using. 20:1 is a little much. We recommend starting at no more than 24:1 then after a couple of gallons move down to a 32:1 mix.

    Like any new engine it takes time for the piston rings and cylinder walls to 'seat in' and a little excess oil blowby can be expected. They will not produce their maximum power until they accrue some running time (miles). The four stroking you're experiencing might go away after break in. Break-in procedure advice will see many saying to vary your speed and not abuse the engine but others will tell you to run it hard and not baby the thing. Use a good quality 2 stroke oil formulated for air cooled engines.

    As for oil around the sparkplug, make sure you have it installed tight. Finger tight then use a wrench or socket and give it an extra 1/4 turn. I use a torque wrench and tighten plugs to 60 to 80 inch pounds but some will say that's overkill.
    You didn't say what carburetor you have so I won't make any recommendations about tuning it. We'd need to know more to help you there.
    Good luck.

    Tom
     
  3. XFITcruizer

    XFITcruizer New Member

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    Thanks for the advice. I have the standard NT style carb, and just tinkered with it a bit. I moved the C or E clip to its leanest position cause I am at 7200 ft altitude.
    - I also took out the core of the muffler.. WOW ITS LOUD!!!!

    -after doing all this, I took it around the block once or twice and I can really feel the difference. I dont think its 4 stroking any more at full throttle but it was hard to tell over all the noise!!

    -I will try to modify the core of the muffler a bit to quiet it down, but also allow more exhaust flow to see if that helps.

    -When I took out the core, I noticed there was a huge kink in the core pipe. It looks extremely restrictive. not sure if that was normal but I will try to modify it some more.

    Thanks guys!.duh.
     
  4. 2door

    2door Moderator
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    Don't run it without the muffler. You'll be buying a new engine. In addition to the annoyance factor the engine will run lean and you'll damage the piston, rings and cylinder wall.
    There are alternatives to the stock muffler but as I suggested above, get the engine broken in before trying to improve performance.

    You're fortunate to have the NT carburetor. It is the simplest to tune and all it really requires is clean fuel. If you haven't done it already, install an in-line fuel filter between the tank and the carb.

    Don't be to anxious to go fast. Take it easy and do it right and you'll be happier with your bike and your engine will like you for it.

    Tom
     

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