Running to rich?

stonegrinder

stonegrinder

New Member
I have a 66cc 2 stroke that was getting top speeds of 25mph and now is topping out at only 15mph. I replaced the spark plug and cleaned the carb with no change. I then noticed that if I took the air filter off, so it's just open, the bike will get back up to 25mph. This told me that it was running to rich, so I thought is was a main jet problem. I replaced the stock 0.70 main jet with a 0.64 and I am still having the same problem. Is it something in the intake maybe? I am new to small motors and am unsure how to proceed. I don't want to screw it up as this in my main commute vehicle. Thank you for anyone that can help this newbie.
 
Try cleaning the air filter. The blowback from the piston port engine can clog the filter pretty quickly....
 
While you have the air filter off to clean it, make sure your choke lever and the choke plate are lined up, and that the nut that holds the two together is good and snug. If it loosens, the vibration of the motor can make the choke plate \swing down and cover some of your intake.
 
I am still getting a lot of oil on the spark plug. I only ran it about 2 blocks and you can see in the pic how dark it is already. I am also getting some oil on top where the spark plug screws in. What do I have going on? Still can't get up to speed.
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hard to tell from the pic, but that oil doesn't seem to be coming from the plug hole, clean it well and spot where it first shows up - most likely the head bolt hole or up from the head gasket - either of those will be same fix for a head gasket not seating
 
How tight are you installing the spark plug. There is at least one set of instructions floating around out there that tells the builder to "finger tighten" the plug. That won't do it. 60 to 80 inch pounds of torque is needed to properly seat the plug/gasket.

Tom
 
I had read that also, finger tight only. I did that and am thinking that's where the leak was. Didn't have the leak before I changed the plug so I went slightly tighter this time. Everything is going back together with the plugs cleaned and gaped, air filter cleaned and oiled, floats bent about a 1/32" towards jets (I think this is lean?), gas at 30:1.
 
Well, gave it a test run today and I can get up to speed just fine and sounds really smooth. The only thing is I have to be easy on the throttle. If I give it to much gas it wants to flood out.
 
If you feed it too fast, it'll choke on it. Eat the pizza a bite at a time, no problem; shove the whole slice in at once, you won't get far.

Go slowly on the throttle as you get up to speed. Sometimes I'll hold it steady until I'm sure the engine's up to speed for that much gas before giving it more.
 
Been running pretty good. The only thing is at ~25 mph it changes tone slightly deeper and feels like it's being held back slightly. What would that be caused by?
 
stonegrinder said:
Well, gave it a test run today and I can get up to speed just fine and sounds really smooth. The only thing is I have to be easy on the throttle. If I give it to much gas it wants to flood out.
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wrong direction with jets...and how in the world does bending the float richen or lean the mixture? that just allows more or less gas into carby...

check tight on ur head studs...somewhere between 125 and 140 INLBS...

as for the aircleaner on the stock carb, it sux...clean then lightly oil it after using a hole punch to put 7 or 8 lil holes in the scotchbrite airfilter...

with that small jet ur more likely to flood out than the next larger...u should also have needle clip positions to choose from...thats really just to dial it in...

good luck
 
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