sotc
Dormant hero!!
ok i bought a dremel and a bur for the heavy work, a polisher and compound for the polishing and this is what ive got so far. need to get a smaller polisher but tell me what im doing right and wrong please
MS260 port job
- Thread starter sotc
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sawinredneck
Treehouser
So far it looks GREAT Willie!! Nice work!!
I don't generaly worry that much about polishing them. Carbon will build up and smooth it out anyway, that's my reasoning at least.
Widdening wil give you the tourqe, then you can get into changing the timing.
Not sure on the 260's, but I don't think it's that hard on them to pul the jug off, so take a little at a time until you like the way it runs. Then leave it alone! You will know when you hit the sweet spot!
Look at loosing the base gasket first, assemble the jug, run a piece of solder in through the exh. port and smash it. Measure the solder as best you can, anything over .017", go get some anerobic sealant and put it back together!
I don't generaly worry that much about polishing them. Carbon will build up and smooth it out anyway, that's my reasoning at least.
Widdening wil give you the tourqe, then you can get into changing the timing.
Not sure on the 260's, but I don't think it's that hard on them to pul the jug off, so take a little at a time until you like the way it runs. Then leave it alone! You will know when you hit the sweet spot!
Look at loosing the base gasket first, assemble the jug, run a piece of solder in through the exh. port and smash it. Measure the solder as best you can, anything over .017", go get some anerobic sealant and put it back together!
sawinredneck
Treehouser
haha
any old solder will work? i had pictured in my mind to run it through the spark plug hole. so your saying then to cut off a half inch long piece and run it through the exhaust right?
YUP!
Ax-Man
Don't make me chop you
Looks good. That flexiable shaft is nice isn't it.
Playdough works just as good as the solder. I never cared for the solder stuff. The playdough worked better for me to measure squish.
Playdough works just as good as the solder. I never cared for the solder stuff. The playdough worked better for me to measure squish.
darkstar
Rockclimber/ treeclimber
Ohh i like this thread please keep the pics coming.
arborworks1
Treehouser
That looks hella familar. Great shots. I'll try to add some of mine tomorrow evening after I disassemble it again.
squisher
THE CALM ONE!!!!
Ya keep the pics and comments coming. I'm real interested in how this turns out for ya Willie. Maybe you can build me a saw next.
arborworks1
Treehouser
Make sure you feather the edges on the piston side. I even put a slight angle on mine.
SO the wider the port is the better. I enlarged mine all around, Better to bellow it out more?
SO the wider the port is the better. I enlarged mine all around, Better to bellow it out more?
sawinredneck
Treehouser
I take as much out as I can on the outside of the casting, carb or muffler side. Then tapper it in.
You don't want to open the intake side too much as it will hook the ring, the ring can expand into the port, and break it. Tears things up. That is what Woodworkingboy was reffering to.
You don't want to open the intake side too much as it will hook the ring, the ring can expand into the port, and break it. Tears things up. That is what Woodworkingboy was reffering to.
arborworks1
Treehouser
Maybe I should clarify. I followed the factory taper and just enlarged it, slightly as this is my first rodeo on chainsaw porting. I just sanded the intake side to smooth out the casting marks.
sawinredneck
Treehouser
Looking at those pics, no wider than the transfers below, but you won't go that wide anyway. All said and done, on my 350 and 346 I took out .120", .060" per side.
A smal saw like this, it doesn't take much.
sawinredneck
Treehouser
If you work from the outside there is all kinds of room
woodworkingboy
TreeHouser
Widening the ports doesn't change timing, raising and lowering does, as does lowering the jug.
It's not such a great idea to just go wailing on the cylinder, it's best to have a plan as to what you want to do in terms of how much, and even know why! Restraint and control are a key to success in modifying a work saw, as well as careful workmanship. The best mods generally are ones where the ports are evenly done on both sides, well balanced, and the top is softly rounded so that when the ring passes over, as in the case of the exhaust and upper transfers, it leaves and returns to the piston groove (ring bulges out when passing over port opening) smoothly and gradually. The chamfer on the port edges prevents the sharp ring edge from catching on the port edge. That will damage the ring quickly. A good rule of thumb for a work saw is to widen the exhaust to 68-70% of the cylinder bore, IF YOU HAVE ENOUGH WIDTH ON THE PISTON SKIRT, and ENOUGH MEAT ON THE OUTSIDES OF THE PORT. If the jug has been lowered, raise the intake by the same amount you have lowered the jug, or raise it until it is just at the bottom of the piston skirt when the stroke is at top dead center, might as well capitalize and get as much gas as possible flowing into the cylinder at the intake stage of the stroke. Widen the intake as material allows, considering the rule of thumb as mentioned. Probably best not to lower the intake at all, you've already done that by lowering the jug.
Raise the exhaust by as much as you've lowered the jug, or slightly more. Too much and you'll have a higher rpm saw, but it won't cut the mustard as far as torque, might fall flat on it's face when under load.
Engine engineers are smart people that know how to get good performance out of stock engines, so remaining within or close to what they had in mind with the stock timing, will give a good working saw, that won't have it's life shortened, generally. If you do all these things well, then you likely want to get on to working on the piston at some point.
Regarding measuring squish, use a soft electrical solder, not the hard kind of solder. Sticking through the exhaust is OK, but the piston rocks on the connecting rod, so just measuring one side can give a false reading, you want to measure on opposing sides, or on four opposing sides is good, as the cylinder bore may not be symmetrical to the base.
I believe you'll get advantage by running high octane in modified saws, and a richer oil gas mix, say 32/1, is likely a good idea too. That's a bit controversial, as well as using dino or synthetic two stroke oil. Opinions may vary.
There is some supplemental reading I can recommend on two cycle engine performance modification, if anyone is interested.
It's helpful to know how to measure timing on the engine, usually done with a timing wheel.
You can take a sharp pencil and outline on the piston the inside shape of the stock port openings. That will tell you how much you can remove off the port. The general rule of thumb is to leave a minimum of 3/32" of skirt width covering the port.
Have fun...modded saws rock!
Jay
It's not such a great idea to just go wailing on the cylinder, it's best to have a plan as to what you want to do in terms of how much, and even know why! Restraint and control are a key to success in modifying a work saw, as well as careful workmanship. The best mods generally are ones where the ports are evenly done on both sides, well balanced, and the top is softly rounded so that when the ring passes over, as in the case of the exhaust and upper transfers, it leaves and returns to the piston groove (ring bulges out when passing over port opening) smoothly and gradually. The chamfer on the port edges prevents the sharp ring edge from catching on the port edge. That will damage the ring quickly. A good rule of thumb for a work saw is to widen the exhaust to 68-70% of the cylinder bore, IF YOU HAVE ENOUGH WIDTH ON THE PISTON SKIRT, and ENOUGH MEAT ON THE OUTSIDES OF THE PORT. If the jug has been lowered, raise the intake by the same amount you have lowered the jug, or raise it until it is just at the bottom of the piston skirt when the stroke is at top dead center, might as well capitalize and get as much gas as possible flowing into the cylinder at the intake stage of the stroke. Widen the intake as material allows, considering the rule of thumb as mentioned. Probably best not to lower the intake at all, you've already done that by lowering the jug.
Raise the exhaust by as much as you've lowered the jug, or slightly more. Too much and you'll have a higher rpm saw, but it won't cut the mustard as far as torque, might fall flat on it's face when under load.
Engine engineers are smart people that know how to get good performance out of stock engines, so remaining within or close to what they had in mind with the stock timing, will give a good working saw, that won't have it's life shortened, generally. If you do all these things well, then you likely want to get on to working on the piston at some point.
Regarding measuring squish, use a soft electrical solder, not the hard kind of solder. Sticking through the exhaust is OK, but the piston rocks on the connecting rod, so just measuring one side can give a false reading, you want to measure on opposing sides, or on four opposing sides is good, as the cylinder bore may not be symmetrical to the base.
I believe you'll get advantage by running high octane in modified saws, and a richer oil gas mix, say 32/1, is likely a good idea too. That's a bit controversial, as well as using dino or synthetic two stroke oil. Opinions may vary.
There is some supplemental reading I can recommend on two cycle engine performance modification, if anyone is interested.
It's helpful to know how to measure timing on the engine, usually done with a timing wheel.
You can take a sharp pencil and outline on the piston the inside shape of the stock port openings. That will tell you how much you can remove off the port. The general rule of thumb is to leave a minimum of 3/32" of skirt width covering the port.
Have fun...modded saws rock!
Jay
woodworkingboy
TreeHouser
"Two Sroke Tuner's Handbook", by Jennings.
Photo of ring damage from a modified exhaust port with too flat a roof. The ring would probably have eventually broken with continued use, and destroyed both the piston and cylinder. Macro lens shot, back from the early days with the Husky 359.
Photo of ring damage from a modified exhaust port with too flat a roof. The ring would probably have eventually broken with continued use, and destroyed both the piston and cylinder. Macro lens shot, back from the early days with the Husky 359.
Attachments
Reddog
TreeHouser
Blue rtv won't take the heat.
See if Al knows what the race saw guys are using.
See if Al knows what the race saw guys are using.
