WANT MORE OUT OF SHINDAIWA 757

[peter92]

Ive got a stock 757 73 cc but want to run a 30'' bar for slabbing
not knowing any thing about saw mods , to me it seems im going to gain speed and loose torque or torque and lower speed , is this correct
what did you do
TIA
peter

 

[tree monkey]

my goal is to gain both. I did one of these a year or so ago and it turned out good

 

[peter92]

my goal is to gain both. I did one of these a year or so ago and it turned out good

well dont stop there haha , what did you end up doing

 

[tree monkey]

cut base & squish, changed port timing, muffler mod, carb work, timing.

 

[rogue60]

To get the best gains its all to do with the legs Peter the skinnier the better kind of like this...


Only joking is a long running joke with the guys porting saw's around here lol... Sorry I am of no help but will be many with good advice..

 

[peter92]

cut base & squish, changed port timing, muffler mod, carb work, timing.

ok lets bring it down a bit with out spending $1,000s
can do the base and squish but don't want a race saw either haha

 

[peter92]

To get the best gains its all to do with the legs Peter the skinnier the better kind of like this...
View attachment 47742

Only joking is a long running joke with the guys porting saw's around here lol... Sorry I am of no help but will be many with good advice..

I needed a good laugh

 

[tree monkey]

I would have to dig up my notes to be more specific. it's a dome piston, I cut the squish flat and milled the piston to match leaving a pop up.

 

[peter92]

I would have to dig up my notes to be more specific. it's a dome piston, I cut the squish flat and milled the piston to match leaving a pop up.

so the 757 has a dome piston, so leaving the base gasket out would still improve it
i dont have a lathe and nobody around my area does saws

 

[tree monkey]

get the squish to around .020". mod the muffler. advance ign timing

 

[peter92]

get the squish to around .020". mod the muffler. advance ign timing

Modding the muff ler , whats the best way of doing that , and advancing the timing , is that done with a wheel

 

[peter92]

get the squish to around .020". mod the muffler. advance ign timing

advance timing , thats done by taking some off the groove where the key way is on the fly wheel , which side of the groove do i take some of , anti clock wise or the other way
also how much would need to come off

 

[peter92]

advance timing , thats done by taking some off the groove where the key way is on the fly wheel , which side of the groove do i take some of , anti clock wise or the other way
also how much would need to come off

will the coil on the 757 allow me to advance the timing , some saws cant be done , i read
"Changing the timing gets into some deep thought and disappointments sometimes because some coils have a built in advance, some coils have a retard and then back to the original position etc. Some coils do not advance or retard"

 

[T.Roller]

I do not know anything about these saws but shaving the key .020 on most Stihls has good results. You need to check the squish after you take out the base gasket. Like Tree Monkey said your looking for around .020.

 

[exSW]

I have one of these in the works. Randy Dunlap has the aftermarket piston,jug and muffler now.

 

[Chainsaw Jim]

Ignition advance isn't a permanent mod. If it doesn't work you can rotate the flywheel back to the original position, or any other position to find the sweet spot. Tree monkey would have warned you if the coil is self advancing, so that's likely no worry.
Muffler mod can be as simple as only enlarging the outlet, or as complex as gutting it of all the baffling and adding multiple outlets with bolt on deflectors.

 

[peter92]

Ignition advance isn't a permanent mod. If it doesn't work you can rotate the flywheel back to the original position, or any other position to find the sweet spot. Tree monkey would have warned you if the coil is self advancing, so that's likely no worry.
Muffler mod can be as simple as only enlarging the outlet, or as complex as gutting it of all the baffling and adding multiple outlets with bolt on deflectors.

yes ive seen some muff mods been done , and some were very well done , I didn't know abut the 1/2 a key way thing , that's a good idea , at least it can be replaced if needed
thanks every one so far for the ideas you have given me , much app it
Peter

 

[peter92]

I do not know anything about these saws but shaving the key .020 on most Stihls has good results. You need to check the squish after you take out the base gasket. Like Tree Monkey said your looking for around .020.

when you say take off .020 thou , is that take off all of the key , as laying the key flat and taking .020 off it

 

[T.Roller]

Yes sir. You want to take it off the side that will allow you to advance the flywheel which would mean turning it counterclockwise.

 

[beaglebriar]

when you say take off .020 thou , is that take off all of the key , as laying the key flat and taking .020 off it

Pull the flywheel, mark the key with a sharpie while it's in the crank, grab the key with a pair of vise grips at the same depth it was in the crank, now carefully file off .020" of the portion that has the sharpie ink on it. Install, rotate flywheel ahead til it butts up to the key and lock it down.