Can't get engine to run right


New Member
Oct 26, 2012
Hey guys. I'm 17 years old and this is my first build. I'm building a sort of board track racer style bike, but I'm at a stand still right now because I can't get the engine to run right.

I bought the black 48 cc engine kit from luckyearlybird on ebay. When I first put it together, it would take about 10 tries to get it running fairly well, but I couldn't get it to go more than about 10 or 15 mph. After a while (15 or 20 miles over a week or so) it started to make these weird sounds and lose power.

I thought it might be something to do with the air/fuel mixture, so I tried to adjust the idle screw and no matter where I adjusted it, it still would not run right. I thought that the carb might be dirty on the inside, so I took it to my auto shop class at school and cleaned it out and sprayed it with some carb cleaner. That didn't seem to help either. Then I thought the oil gas mixture was the problem. I was using about 16:1 so I switched to 24:1 and that didn't seem to help either. Then I thought it might be the spark plug, so I bought a NGK plugs and that didn't really do anything...

Now when I release the clutch, the engine sometimes won't start up and will almost stop the bike - it feels like it drags it to a stop. And when I do get it to start it has this klanking or knocking sound coming from the engine. I took off the cover on the left side where the magneto is and there were metal shavings in it.

Does anyone know what the problem could be? - I don't think it's the carb or the spark plug.



Well-Known Member
Sep 30, 2012
sounds bad - with left & right covers off, try (gently) prying each end of the crankshaft up a bit - if either side moves, you've lost the main bearing on that side

if those are OK, then maybe your stator or rotor is misaligned and is rubbing together - you should be able to straighten that out OK, but while it is off, check your seal on that side for damage too


May 29, 2011
Sounds like he sheered the key way on the magnet and timing is out of wack that what happen to me .I had a new engine do that same thing with knocking.I fixed the key way and it ran fine but I did not run it very long when it started knocking shut it right down.