Post by mcycle12 on Feb 20, 2017 17:37:31 GMT -5
I kind of stole stole a thread from another poster last year who had a similar problem. Not wanting to go back to that thread, I created a new one. Here is the issue:
The saw starts fine, idles and accelerates fine, but when you put the chain to wood it lasts about 5 seconds before bogging out. Pull it out of the wood and it will accelerate again. Put it in the wood and seconds later it is dying. Here's what I've done to it:
Rebuilt the original Tillotson carb with a kit. Carb was cleaned in an ultrasonic cleaner and blown out. No change in running.
Found a NOS replacement Walbro carb on E-Bay. Put it on, along with new fuel line from the metal elbow back. No change...still bogging down.
Both carburetors were adjusted right on the high/low settings. The engine is running exactly the same with both carbs. The saw runs great until you put a load on it.
Checked the duckbill in the fuel cap. Cleaned the sintered brass plug in carb cleaner. Still bogging out.
Ran the saw with the vent in the cap open. No change.
Checked the line from the carb to the tank with a vacuum brake bleeder to see if it is sucking air. The line holds a vacuum without a problem when the end is plugged. No leaks.
Installed a new spark plug. No change. The plug is nice and tan when I pull it after cutting the ignition during a bogging spell. I think it's fuel delivery, not ignition.
Checked the impulse hole in the carb mount. When I put compressed air in it, the piston moves. I assume that means it's working. I'm using stock gaskets with the impulse hole lined up. The carburetor primed about about 5 pulls after I replaced the line, so I believe the pulse is working.
I'm at my wits end with this saw. All my mechanical knowledge tells me this is a fuel starvation issue. I really like it and want it running right, but it's driving me nuts.
Questions: If the saw is low on compression, will the impulse needed to operate the fuel pump be weak enough so that not enough fuel is pumped? I've yet to test the compression on this saw. How about the reeds? Will weak or broken reeds cause this problem?
This saw ran fine up until the time this condition suddenly began occurring.
I tested the compression and it was 60psi. I've got that issue rectified now and it's 165psi... plus.
Still the same engine performance though. Bogs down under load and won't recover until you take the load off.
I put 40psi into the spark plug hole while holding the flywheel with a wrench and only hear a little hiss thorough the carb.....impulse port I suspect.
Tilting the saw from one side to the other doesn't seem to make any difference.
This one is driving me nuts. Plus, I've got quite a bit of money wrapped up in it now.
The saw starts fine, idles and accelerates fine, but when you put the chain to wood it lasts about 5 seconds before bogging out. Pull it out of the wood and it will accelerate again. Put it in the wood and seconds later it is dying. Here's what I've done to it:
Rebuilt the original Tillotson carb with a kit. Carb was cleaned in an ultrasonic cleaner and blown out. No change in running.
Found a NOS replacement Walbro carb on E-Bay. Put it on, along with new fuel line from the metal elbow back. No change...still bogging down.
Both carburetors were adjusted right on the high/low settings. The engine is running exactly the same with both carbs. The saw runs great until you put a load on it.
Checked the duckbill in the fuel cap. Cleaned the sintered brass plug in carb cleaner. Still bogging out.
Ran the saw with the vent in the cap open. No change.
Checked the line from the carb to the tank with a vacuum brake bleeder to see if it is sucking air. The line holds a vacuum without a problem when the end is plugged. No leaks.
Installed a new spark plug. No change. The plug is nice and tan when I pull it after cutting the ignition during a bogging spell. I think it's fuel delivery, not ignition.
Checked the impulse hole in the carb mount. When I put compressed air in it, the piston moves. I assume that means it's working. I'm using stock gaskets with the impulse hole lined up. The carburetor primed about about 5 pulls after I replaced the line, so I believe the pulse is working.
I'm at my wits end with this saw. All my mechanical knowledge tells me this is a fuel starvation issue. I really like it and want it running right, but it's driving me nuts.
Questions: If the saw is low on compression, will the impulse needed to operate the fuel pump be weak enough so that not enough fuel is pumped? I've yet to test the compression on this saw. How about the reeds? Will weak or broken reeds cause this problem?
This saw ran fine up until the time this condition suddenly began occurring.
I tested the compression and it was 60psi. I've got that issue rectified now and it's 165psi... plus.
Still the same engine performance though. Bogs down under load and won't recover until you take the load off.
I put 40psi into the spark plug hole while holding the flywheel with a wrench and only hear a little hiss thorough the carb.....impulse port I suspect.
Tilting the saw from one side to the other doesn't seem to make any difference.
This one is driving me nuts. Plus, I've got quite a bit of money wrapped up in it now.
