got it running tonight! started dialing in the screws and BAM!! shut down immediatly. Freaking out for a second i collected myself and then took off the starter cover. Found a sheared flywheel key. THe BAM when it shut down im assuming was abckfire since the timing was off. Im scared to cinch the flywheel nut too tight after pulling the threads off one on a weedeater. I saw lakesides post about 37 ft lbs and im gonna go try it now. Lukily my dealer was open on christmas eve!! She sure sounded good before it shut down. seems like it will be idleing higher than a unported saw, is that normal? i couldnt find a good low idle+good off the bottom accel setting.
660 Porting, with pictures. Need Some Input. (Pictures are Huge)
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stihlboy
Guess who's back
that bam could have broken the crank
neutral4x4
ArboristSite Operative
saw porting
Did you end up chamfering the port edges? You really need to do that if you expect your rings to last.
Make a port map before and after every port job to find out where everything needs to be moved to.
For port width: measure the bore diameter. Multiply that by .67 (67% is a safe bet. You can go up to 70%, but then your rings will start wearing out faster).
Put a piece of paper in the bore over your port and rub a dull pencil over it to get a rubbing of the port shape. When you lay out that piece of paper, your port can be as wide as the calculation you did above (unless your piston skirt is smaller than that number or your ring ends fall within that zone).
I always widen the exhaust to 67% of the bore, then measure the area of the smallest point in the carb and make the intake the same area (widen it to that point, and make sure your piston skirt doesn't fit into the port).
I usually raise the exhaust and lower the intake if I'm looking for crazy high RPMs (I like working on mopeds and small motorcycles), but on a chainsaw, DON'T raise or lower ports. You want all the torque you can get. Raising and lowering ports will shift the power band up and kill the torque.
If you sheared the woodruff key, there are a few reasons that might have happened.
1) You didn't tighten the flywheel enough. I hope that was the reason.
2) You snagged and probably broke a ring in your larger ports.
3) You dialed the jetting in wrong and you seized the piston in the cylinder.
If you lowered the exhaust at all, check to make sure that the ring isn't showing in the exhaust port at BDC, if it is, throw out the cylinder. Don't run it. If the ring isn't in contact with the cylinder wall at BDC, it won't be able to cool off and will expand enough to seize in the bore after a few minutes running.
Thats just speaking from experience. Take it with a grain of salt. If you think it should run, try it out. If you're worried you went too far, it'll be better to buy a new cylinder than a whole new saw.
Eric
Did you end up chamfering the port edges? You really need to do that if you expect your rings to last.
Make a port map before and after every port job to find out where everything needs to be moved to.
For port width: measure the bore diameter. Multiply that by .67 (67% is a safe bet. You can go up to 70%, but then your rings will start wearing out faster).
Put a piece of paper in the bore over your port and rub a dull pencil over it to get a rubbing of the port shape. When you lay out that piece of paper, your port can be as wide as the calculation you did above (unless your piston skirt is smaller than that number or your ring ends fall within that zone).
I always widen the exhaust to 67% of the bore, then measure the area of the smallest point in the carb and make the intake the same area (widen it to that point, and make sure your piston skirt doesn't fit into the port).
I usually raise the exhaust and lower the intake if I'm looking for crazy high RPMs (I like working on mopeds and small motorcycles), but on a chainsaw, DON'T raise or lower ports. You want all the torque you can get. Raising and lowering ports will shift the power band up and kill the torque.
If you sheared the woodruff key, there are a few reasons that might have happened.
1) You didn't tighten the flywheel enough. I hope that was the reason.
2) You snagged and probably broke a ring in your larger ports.
3) You dialed the jetting in wrong and you seized the piston in the cylinder.
If you lowered the exhaust at all, check to make sure that the ring isn't showing in the exhaust port at BDC, if it is, throw out the cylinder. Don't run it. If the ring isn't in contact with the cylinder wall at BDC, it won't be able to cool off and will expand enough to seize in the bore after a few minutes running.
Thats just speaking from experience. Take it with a grain of salt. If you think it should run, try it out. If you're worried you went too far, it'll be better to buy a new cylinder than a whole new saw.
Eric
yeah when it shut down so abruptly i was scared it was a hung ring or a broken rod or crank. It was only the flywheel key sheared. Im still scared to torque it down to the 37 foot pounds. maybe the steel used on the weedeater cranks arent quite as strong and thats why i pull the threads off. I dont know but i REALLY dont want to do that to this saw.
Either torque it, or shear another key. You'll probably pull the threads out of the nut before the crank.
i use air tools and just tap the flywheel on with 1/2 gun. by tap i mean tap lightly
i also have 18v 1/2 dewalt impact that gets stuff like this plenty tight.
you can get it tight enough , hold hte flywheel in your hand dock it tight with a rubber malet. that should get it plenty tight. a couple good wacks is all itl take.
i also have 18v 1/2 dewalt impact that gets stuff like this plenty tight.
you can get it tight enough , hold hte flywheel in your hand dock it tight with a rubber malet. that should get it plenty tight. a couple good wacks is all itl take.
EHHH, dont tell him that, he might destroy his saw.
impacts + inexperience = bad
Get a decent torque wrench at sears.
parrisw
Tree Freak
:agree2:
Boleclimber
ArboristSite Guru
Use a rope coiled through the spark plug to keep the crank from rotating and get yourself a torque wrench to set the correct foot pounds.
If your saw has a washer under the nut, make sure the washer is oriented correctly.
I am not sure how picky Stihls are about washer orientation, I know huskys will cut a key way easily when the washer is backwards.
If you have a good hand for estimating torque, bypass the torque wrench; I dont recommend you bypass if this is your first saw build.
There is a toothpaste trick you can use. Smear tooth paste on the crank shaft before you put the flywheel on. The diatoms (grit) in the paste helps the flywheel hold to the shaft, putting less pressure on your key way.
If your saw has a washer under the nut, make sure the washer is oriented correctly.
I am not sure how picky Stihls are about washer orientation, I know huskys will cut a key way easily when the washer is backwards.
If you have a good hand for estimating torque, bypass the torque wrench; I dont recommend you bypass if this is your first saw build.
There is a toothpaste trick you can use. Smear tooth paste on the crank shaft before you put the flywheel on. The diatoms (grit) in the paste helps the flywheel hold to the shaft, putting less pressure on your key way.
This is not the first saw i have built. This is the first saw i have ported. I have the torque wrench, in both 1/2 and 3/8 drive. Its just that when you screw up the threads on one crank it makes you leary on every one after that. But it was a WeedEater and they are junk anyway. I use a piece of 3/8 silicone tubing folded over and shoved in the plug hole as my piston stop it seems to work good, it held the crank still for the 37 foot pounds at least! I cant see my self using the impact driver on a saw, not that your doing it wrong, im sure your careful enough to not screw things up, but i would prefer the torque wrench.
Wow, ok so i got it running last night and cut some slabs off a 26-28 inch oak thats been down a couple months. I got the mixture screws right, after some tedious dialing in. I first got the high set to where it was barely four stroking at WOT out of the cut. Made half a pass through the wood and dialed it in a little more. did that twice till i was satisfied with it. I was at first dissapointed with how the saw performed after the porting, it wasnt what i was expecting but it quickly turned into something better! I had this illusion that after porting it would be like that v8 chainsaw or something, since i had never ran a ported saw i didnt know what to expect. i especially didnt know what gains i would get since i never ran the saw in stock form. Once it was dialed in and running good i took it for some cuts though that oak. It cut faster than my 6401BB but i wasnt overly impressed at the cut speed. It wasnt till I dug the spikes in and really torqued up on the handle that i realized that this saw had some realy power/torque. I could use my knee to push up and be pulling up on the rear handle as hard as i wanted and the rpms didnt drop any significant amount and it never bogged down. True i was only running a 24 inch bar but it was fully burried with a new semi chisel stihl chain. Im so impressed with this saw more because i pulled the bar and chain off and put it on my uncles 660 and his saw felt like dropping back down to the 036. I think the next step is to slowly bring the rakers down and see what this saw can do, with out over loading it. Thanks to all of you that helped me with this project. Next im gonna port the muffler. Im kinda hesitant to do that. I ported the 039 and I have to wear ear plugs when i run it.
