parrishturf
ArboristSite Operative
I am new to posting so bare with me. I have had some success hopping up a 441. And question some of my results. Can anyone confirm or refute any of the following: (I am shocked this saw stayed together, it's remarkable)
Pre mod stats:
Max rpm 13,000 open shaft
140 psi Comp
Throttle response B-
Saw is high milage
Mods:
+10% Width Intake and Exaust Port.
Open and smooth all passages.
Taper ends of transfer ports under jug, and open to match case opening. (I have not knife edged the bridge between frt and r ports yet, just radiused.)
Enlarge and port match Fuel intake, Air/Strato intake, exaust.
Enlarge radius on jug skirt to allow smother flow to transfer ports.
Removed base gasket.
Drilled Muffler in stages Stock, +1 3/8" hole then, +2 3/8" holes, left original port open.
Did not remove Choke plate.
Results:
OMG!!!
The muffler drilling added about 750 RPM each port.
The base gasket took compression from 140 to 175 and no leakdown at 1min.
PlayDoe Squish test yields clearence all around top of piston, But close.
Final open shaft rpm 15760 tuned lean with no burble.
Carb settings for 13500 or even the high and lean 15760 were surprisingly tight.
Throttle response A+, cranks on 1/2 choke first pull.
Maybe to much info but, I did not think this saw with the strato ports would even run on the stock carberator after opening everything up. The muffler mods are crude and worked well.
So here is my question, how can this saw, after opening every thing up, require tighter fuel settings?
Keep in mind this is no load data and all might change, but, after reading all the questionable performance gains that most have experienced, I thought I would ask a more expert group.
Future:
Slot flywheel Advance ???degrees
Polish and open carb.
Polish and open strato port.
If the engine wants more air the strato port might just do it...
I know there is a pot full of fuel left on stock carb...
All comments welcome...
Pre mod stats:
Max rpm 13,000 open shaft
140 psi Comp
Throttle response B-
Saw is high milage
Mods:
+10% Width Intake and Exaust Port.
Open and smooth all passages.
Taper ends of transfer ports under jug, and open to match case opening. (I have not knife edged the bridge between frt and r ports yet, just radiused.)
Enlarge and port match Fuel intake, Air/Strato intake, exaust.
Enlarge radius on jug skirt to allow smother flow to transfer ports.
Removed base gasket.
Drilled Muffler in stages Stock, +1 3/8" hole then, +2 3/8" holes, left original port open.
Did not remove Choke plate.
Results:
OMG!!!
The muffler drilling added about 750 RPM each port.
The base gasket took compression from 140 to 175 and no leakdown at 1min.
PlayDoe Squish test yields clearence all around top of piston, But close.
Final open shaft rpm 15760 tuned lean with no burble.
Carb settings for 13500 or even the high and lean 15760 were surprisingly tight.
Throttle response A+, cranks on 1/2 choke first pull.
Maybe to much info but, I did not think this saw with the strato ports would even run on the stock carberator after opening everything up. The muffler mods are crude and worked well.
So here is my question, how can this saw, after opening every thing up, require tighter fuel settings?
Keep in mind this is no load data and all might change, but, after reading all the questionable performance gains that most have experienced, I thought I would ask a more expert group.
Future:
Slot flywheel Advance ???degrees
Polish and open carb.
Polish and open strato port.
If the engine wants more air the strato port might just do it...
I know there is a pot full of fuel left on stock carb...
All comments welcome...