Engine Trouble Mr Smith


Bradley Smith

First all hello. I'm a brand new motorized bike ower. I have a two-stroke mounted to my Trek frame. I have been fixed everything I can on it and have now tackled performance. I bought it used so I don't have any history on the bike other than what I have learned that was wrong with it after I bought it, for example, the throttle was clamped in the WOT position. I had almost everything dialed in until I changed to high-octane fuel. I have since switched back by emptying the tank with the 87 octane. Several problems now.

  1. Under load (me on the bike) it will not reach the higher rpm as when I'm off the bike. When I'm off the bike it builds up slowly to sounding like a chainsaw, redlining I bet.
  2. Under load, it sounds like 4 stroking and then from cold to warm up there is a brief moment that it will speed up just a bit then bog back down the rest of the ride.
  3. I take the fuel screw out and I suddenly get a combination of more power and a little less 4 stroking.
  4. I have leaned out just the jet needle (when I did that before I used the higher octane it ran well at that position which was at the top.
  5. I did have it going about 25 mph but now it is going 10-15 at most.
  6. When I am off the bike and WOT it takes about 8 seconds to redline
Things I have tried.
  1. Cleaned the air filter
  2. Checked the float - all good (still floats no holes)
  3. Cleaned the carb - clean
  4. set the jet needle - Top to / second to top
  5. set the fuel screw - Pulled out right now and more power
  6. Tighten bolts all around - fixed mounts
  7. Adjusted the throttle cable so it opens and closes all the way
I think I need chain oil but it isn't hard to move the chain by hand when the clutch is disengaged. I do see oil spills on the top of the carburetor and top of the crankshaft like a head gasket leak but the heads seem tight. I don't have a torque wrench or a compression tester.

The question is why can I get it to rev like a pro but when I sit on the bit it bogs and never increases in the RPM even going downhill the bike bogs.