SteveSr
Addicted to ArboristSite
Hello,
Here is a little challenge for your diagnostic noggin on a Saturday afternoon!
The Saw: Husky 41 with new OEM impulse tube, manifold, OEM fuel line, new OEM fuel pickup. Muffler screen is installed and clear. Piston looks good through exhaust port. Engine passes BOTH pressure and Vacuum. Fuel is fresh from the pump 50:1 Non-E with Red Armor. The serial number is 6415588.
The Carb: The saw was found with a Zama C1Q-29E. The carb was disassembled and cleaned with aerosol carb cleaner (Berryman's B-12) and a new OEM kit was installed. I couldn't find this carb model in any of the IPLs but may be similar to a Walbro WT-239 which was listed in later versions of this saw.
Carb Settings - As Found:
"L" = 2 1/2
"H" = 2 1/8
These are the basic settings listed for the WT-239 in the Rev 2 - 12/1995 Operators manual.
Symptoms (i.e. Clues!):
1. Saw will start and run on part throttle but immediately bog when trying to accelerate
2. Saw will not idle and just dies if you release the part throttle lock.
3. If I adjust the "L" screw richer (3 1/8 turn) the saw will idle.
4. The idle is responsive to tuning about the 3 1/8 setting.
5. At this new "L" setting the saw will still bog off idle but you can get it to transition to WOT.
6. WOT tachs out at 13,400 (Max is 13,000) and it sounds like it is 4-stroking at this RPM.
7. Adjusting the "H" screw has little/no effect on the WOT speed.
8. After attempting to tune the saw I removed the spark plug and it was black.
Let me know if I can answer any questions or clarify anything.
Your thoughts on the carb defect(s) that might be causing this behavior. Please justify your answer.
Thanks,
Steve
Here is a little challenge for your diagnostic noggin on a Saturday afternoon!
The Saw: Husky 41 with new OEM impulse tube, manifold, OEM fuel line, new OEM fuel pickup. Muffler screen is installed and clear. Piston looks good through exhaust port. Engine passes BOTH pressure and Vacuum. Fuel is fresh from the pump 50:1 Non-E with Red Armor. The serial number is 6415588.
The Carb: The saw was found with a Zama C1Q-29E. The carb was disassembled and cleaned with aerosol carb cleaner (Berryman's B-12) and a new OEM kit was installed. I couldn't find this carb model in any of the IPLs but may be similar to a Walbro WT-239 which was listed in later versions of this saw.
Carb Settings - As Found:
"L" = 2 1/2
"H" = 2 1/8
These are the basic settings listed for the WT-239 in the Rev 2 - 12/1995 Operators manual.
Symptoms (i.e. Clues!):
1. Saw will start and run on part throttle but immediately bog when trying to accelerate
2. Saw will not idle and just dies if you release the part throttle lock.
3. If I adjust the "L" screw richer (3 1/8 turn) the saw will idle.
4. The idle is responsive to tuning about the 3 1/8 setting.
5. At this new "L" setting the saw will still bog off idle but you can get it to transition to WOT.
6. WOT tachs out at 13,400 (Max is 13,000) and it sounds like it is 4-stroking at this RPM.
7. Adjusting the "H" screw has little/no effect on the WOT speed.
8. After attempting to tune the saw I removed the spark plug and it was black.
Let me know if I can answer any questions or clarify anything.
Your thoughts on the carb defect(s) that might be causing this behavior. Please justify your answer.
Thanks,
Steve
