I have an older PS-420 Dolmar. I loved that saw until a year or so ago when it started acting up and ran funny. I have never been able to get her back to her old glory.
Symptoms and Information:
Saw will go from idle up in RPM smoothly until a certain speed, then shuts completely down, even if the throttle lever is released. It will not recover if a certain RPM is exceeded. Seems coil related? I'd hate to put a 3rd coil on this thing.
Saw will start and idle with a new Zama carb. I ruined the original Walbro trying to track down a check valve. Some on this forum mentioned trouble with a check valve in the carb on theirs.
https://www.arboristsite.com/threads/dolmar-ps-420-issues.369459/
Saw seems to have as good or better compression than my other saws, especially for only 42 cc. Piston seems in decent condition. I had the cylinder off at one point.
I replaced the original coil with a 421 coil, used, from Chainsawr.
Plug has spark, but not sure if it is working totally right.
I replaced sparkplug with another identical one, no better performance.
Thought maybe fuel tank vent not allowing enough fuel to be pulled into the carb?
I turned the running saw on it's side and cracked open the fuel fill plug. It still won't go up in RPM past a certain point, as if the kill switch is hit once it passes a certain RPM.
I took it totally apart. The impulse line and fuel lines are replaced and clear flowing. I even checked the impulse line fitting on the cylinder - it is clean and clear.
I like the saw and want to make it run. I converted it to a rim sprocket. It is a nice handling saw.
It holds vacuum and pressure, so I don't think it is a seal issue, at least not while cold.
Piston seems in decent condition.
A member on here mentioned he had trouble with a check valve in the Makita equivalent of this saw and fixed his with a new carb. This one has a new Zama.
Symptoms and Information:
Saw will go from idle up in RPM smoothly until a certain speed, then shuts completely down, even if the throttle lever is released. It will not recover if a certain RPM is exceeded. Seems coil related? I'd hate to put a 3rd coil on this thing.
Saw will start and idle with a new Zama carb. I ruined the original Walbro trying to track down a check valve. Some on this forum mentioned trouble with a check valve in the carb on theirs.
https://www.arboristsite.com/threads/dolmar-ps-420-issues.369459/
Saw seems to have as good or better compression than my other saws, especially for only 42 cc. Piston seems in decent condition. I had the cylinder off at one point.
I replaced the original coil with a 421 coil, used, from Chainsawr.
Plug has spark, but not sure if it is working totally right.
I replaced sparkplug with another identical one, no better performance.
Thought maybe fuel tank vent not allowing enough fuel to be pulled into the carb?
I turned the running saw on it's side and cracked open the fuel fill plug. It still won't go up in RPM past a certain point, as if the kill switch is hit once it passes a certain RPM.
I took it totally apart. The impulse line and fuel lines are replaced and clear flowing. I even checked the impulse line fitting on the cylinder - it is clean and clear.
I like the saw and want to make it run. I converted it to a rim sprocket. It is a nice handling saw.
It holds vacuum and pressure, so I don't think it is a seal issue, at least not while cold.
Piston seems in decent condition.
A member on here mentioned he had trouble with a check valve in the Makita equivalent of this saw and fixed his with a new carb. This one has a new Zama.
