Two things to consider regarding pressure and vacuum. First, if you’re using a Mityvac, it measures vacuum in inHg, with roughly 2 inHg equaling 1 psi. So make sure the vacuum scale is around 15 and the pressure scale around 7. Second, turn the crank over multiple times under vacuum.
My initial suggestion is to lean out the L screw on the saw slightly. While it may not be the main issue, it’s definitely too rich and not quite right.
The fluctuation at full throttle suggests some restriction, which could be due to the tank vent, a carb/fuel blockage, or an intermittent air leak.
Amazon carbs can be hit or miss—your success rate is likely below 50%. I always advise people to hold onto their original parts unless they’re beyond repair.
Also, whenever you’re explaining something like this, it’s helpful to include a short video clip to illustrate your points, for the reasons I’ve mentioned.
In your case, I’d recommend retesting the vacuum at 15-20 inHg and turning the crank at the same time. If everything checks out (and you haven’t used rubber to block the intake), make sure the tank vent is functioning, the filter is clean, the fuel line is in good condition, flexible, and properly sealed. Then, try putting the knockoff carb kit into the OEM carb and check that all passages flow properly with brake cleaner under pressure.
Diagnosing faults can be a long and frustrating process, especially if you’re not used to it. Take a step back, breathe, and approach it with a clear head—problems get solved faster that way.
Apologies if I’ve repeated anything you’ve already tried. The thread’s gotten quite long, so I may not remember everything.
My initial suggestion is to lean out the L screw on the saw slightly. While it may not be the main issue, it’s definitely too rich and not quite right.
The fluctuation at full throttle suggests some restriction, which could be due to the tank vent, a carb/fuel blockage, or an intermittent air leak.
Amazon carbs can be hit or miss—your success rate is likely below 50%. I always advise people to hold onto their original parts unless they’re beyond repair.
Also, whenever you’re explaining something like this, it’s helpful to include a short video clip to illustrate your points, for the reasons I’ve mentioned.
In your case, I’d recommend retesting the vacuum at 15-20 inHg and turning the crank at the same time. If everything checks out (and you haven’t used rubber to block the intake), make sure the tank vent is functioning, the filter is clean, the fuel line is in good condition, flexible, and properly sealed. Then, try putting the knockoff carb kit into the OEM carb and check that all passages flow properly with brake cleaner under pressure.
Diagnosing faults can be a long and frustrating process, especially if you’re not used to it. Take a step back, breathe, and approach it with a clear head—problems get solved faster that way.
Apologies if I’ve repeated anything you’ve already tried. The thread’s gotten quite long, so I may not remember everything.
