Ohlen C
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- Nov 20, 2013
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Hello everyone! New guy here. I'm hoping to pick the brains of some of the experienced chainsaw mechanics in here.
A few years ago, I resurrected an old saw that had been floating around the farm. (Broken fuel pickup, starter spring) It is a Husqvarna L77 SN#1029915. I don't even know how old this saw is, but I do know that parts are hard to find, if you can find them at all.
This saw has always been hard to impossible to restart once it has sat for a few minutes while hot. After reading and watching about carb adjustments on chainsaws, I noticed that when free running at WOT the saw quickly gets to operating speed and starts out 4 stroking, then quickly the rpms go up and the saw is running too lean after, maybe, 5 sec. of WOT.
The other day I noticed the muffler was wet after a few pulls when I was trying to get it started again. The saw had sat 5 - 10 minutes on the ground after ~15 minutes of use. I thought that there were 2 likely candidates, the fuel air vent, and the diaphragm needle. I blew into the tank vent hose and it was difficult to move air in any direction, so I removed the valve. I noticed a hole in the top and stuck a wire in it. This loosened the ball again, but it would not stay loose. I then took a nail and ground it down so that I could use it as a punch and back out the spring pin. I tried to locate any obstructions, but was unable to keep the ball from getting stuck at the end. Then I dropped the ball, and that ended that. I put a small piece of shop towel into the valve and reassembled it. I could blow through the valve without much difficulty, so I started the saw to see what would happen. The saw idled beautifully, but when I went WOT it 4 stroked for a few seconds then the RPMs started increasing and the saw was soon in a lean condition. I removed the fuel hose and could blow into it easily, then I took off the top of the carburetor. I noticed what seemed a lot of sawdust in there, so I sprayed it out with carb cleaner and tried starting the saw again. The saw now 4 stroked for a good 9-10 seconds before it again started picking up speed and running lean. I removed the diaphragm side and everything seemed clean on this side. I sprayed out the seats and orifices anyway in case there was something I was missing. Same symptoms.
On making the carb adjustments.
The low speed needle seemed normal. If the screw is adjusted too far in either direction, the saw won’t run. I adjusted for highest speed then made it a little rich.
The high speed valve will stop the saw quickly when closed. I can’t make the saw stop by adjusting the screw all the way out. From ~1 1/2 to all the way out, there is no discernable difference to me. I can set it where it just starts 4 stroking at WOT, and it stays there a few seconds then leans out and the engine races.
Is this normal? Is there an obstruction I might be missing? What should I try next?
Thanks for taking the time to read this.
A few years ago, I resurrected an old saw that had been floating around the farm. (Broken fuel pickup, starter spring) It is a Husqvarna L77 SN#1029915. I don't even know how old this saw is, but I do know that parts are hard to find, if you can find them at all.
This saw has always been hard to impossible to restart once it has sat for a few minutes while hot. After reading and watching about carb adjustments on chainsaws, I noticed that when free running at WOT the saw quickly gets to operating speed and starts out 4 stroking, then quickly the rpms go up and the saw is running too lean after, maybe, 5 sec. of WOT.
The other day I noticed the muffler was wet after a few pulls when I was trying to get it started again. The saw had sat 5 - 10 minutes on the ground after ~15 minutes of use. I thought that there were 2 likely candidates, the fuel air vent, and the diaphragm needle. I blew into the tank vent hose and it was difficult to move air in any direction, so I removed the valve. I noticed a hole in the top and stuck a wire in it. This loosened the ball again, but it would not stay loose. I then took a nail and ground it down so that I could use it as a punch and back out the spring pin. I tried to locate any obstructions, but was unable to keep the ball from getting stuck at the end. Then I dropped the ball, and that ended that. I put a small piece of shop towel into the valve and reassembled it. I could blow through the valve without much difficulty, so I started the saw to see what would happen. The saw idled beautifully, but when I went WOT it 4 stroked for a few seconds then the RPMs started increasing and the saw was soon in a lean condition. I removed the fuel hose and could blow into it easily, then I took off the top of the carburetor. I noticed what seemed a lot of sawdust in there, so I sprayed it out with carb cleaner and tried starting the saw again. The saw now 4 stroked for a good 9-10 seconds before it again started picking up speed and running lean. I removed the diaphragm side and everything seemed clean on this side. I sprayed out the seats and orifices anyway in case there was something I was missing. Same symptoms.
On making the carb adjustments.
The low speed needle seemed normal. If the screw is adjusted too far in either direction, the saw won’t run. I adjusted for highest speed then made it a little rich.
The high speed valve will stop the saw quickly when closed. I can’t make the saw stop by adjusting the screw all the way out. From ~1 1/2 to all the way out, there is no discernable difference to me. I can set it where it just starts 4 stroking at WOT, and it stays there a few seconds then leans out and the engine races.
Is this normal? Is there an obstruction I might be missing? What should I try next?
Thanks for taking the time to read this.
