I bought several "80cc" motors from BGF and both of the ones that I have mounted have the same problem- after a few seconds at wide open throttle &high RPM the motor would just fall on its face.
It would lose all power until I gave it a few seconds rest, then pull hard again for a few seconds only to fail again.
Reading the many threads about this and similar problems, I found conflicting opinions as to whether the stock jet was too large or too small. I was just about to drill the thing out on one carb and solder/ drill another just to see what difference it would make when I noticed something- neither of the needles I was looking at had much taper at all. Nothing like the needle on a Holley carb like what I used to work on. So I took one of the little boogers to the drill press and put some sand paper to it- concentrating on the area near the tip. I didnt even measure it before or after, I just went by instinct and removed more metal where I figured more gas was needed. Back in the motor and it runs a bit rich. Wont idle at all. I lower the needle one notch. Whamo! my power band is even throughout! great idle and no sputter even at WOT downhill!
This might just be a bad batch of needles, but if anybody else has the same problem, it si worth a shot- I didnt even have to take the carb off the bike! Just dont take off too much metal- I think I came close on mine with the stock intake and no porting. Thats ok though because these motors wont stay stock for long! A little port and polish + improved air filter should increase airflow enough to compensate for the extra fuel. Or I could build the dual RAM air intake I have been dreaming up...
It would lose all power until I gave it a few seconds rest, then pull hard again for a few seconds only to fail again.
Reading the many threads about this and similar problems, I found conflicting opinions as to whether the stock jet was too large or too small. I was just about to drill the thing out on one carb and solder/ drill another just to see what difference it would make when I noticed something- neither of the needles I was looking at had much taper at all. Nothing like the needle on a Holley carb like what I used to work on. So I took one of the little boogers to the drill press and put some sand paper to it- concentrating on the area near the tip. I didnt even measure it before or after, I just went by instinct and removed more metal where I figured more gas was needed. Back in the motor and it runs a bit rich. Wont idle at all. I lower the needle one notch. Whamo! my power band is even throughout! great idle and no sputter even at WOT downhill!
This might just be a bad batch of needles, but if anybody else has the same problem, it si worth a shot- I didnt even have to take the carb off the bike! Just dont take off too much metal- I think I came close on mine with the stock intake and no porting. Thats ok though because these motors wont stay stock for long! A little port and polish + improved air filter should increase airflow enough to compensate for the extra fuel. Or I could build the dual RAM air intake I have been dreaming up...
