The Colonel
Well-Known Member
I am having a really hard time with tuning a PHBN 17.5 carb. Not the main jet, but the low end. I can't get it NOT to stumble from idle to 1/8th throttle.
Scooter is a 2001 Aprilia Scarabeo. Cylinder is a Corsa, airbox is stock, but desnorkeled. Main jet is a 96, pilot is a 34 - stock reeds. Nice brown plugs.
It can't leave the driveway with the stock PHBN 17.5 (A-2) needle set on lean. It fouls out. I tried an A-8 needle. Runs too rich on it's leanest setting...but doesn't foul out. Then, for grins, I tried the stock needle from the stock 12mm carb. I think it's an A-11. Almost no taper. It's like a brick. Anyway...it runs OK on the leanest setting. Everything I have read says that a 34 pilot is too lean for that cylinder...let alone the stock needle set leaner than the stock 50cc setup! I don't trust it. There isn't any dead spots or bogs. There is a rattle when I close the throttle down to 1/8th, but if I add the choke, it stalls out. Sounds lean, acts rich. Any ideas??
Scooter is a 2001 Aprilia Scarabeo. Cylinder is a Corsa, airbox is stock, but desnorkeled. Main jet is a 96, pilot is a 34 - stock reeds. Nice brown plugs.
It can't leave the driveway with the stock PHBN 17.5 (A-2) needle set on lean. It fouls out. I tried an A-8 needle. Runs too rich on it's leanest setting...but doesn't foul out. Then, for grins, I tried the stock needle from the stock 12mm carb. I think it's an A-11. Almost no taper. It's like a brick. Anyway...it runs OK on the leanest setting. Everything I have read says that a 34 pilot is too lean for that cylinder...let alone the stock needle set leaner than the stock 50cc setup! I don't trust it. There isn't any dead spots or bogs. There is a rattle when I close the throttle down to 1/8th, but if I add the choke, it stalls out. Sounds lean, acts rich. Any ideas??