GoBigBlue1984
Right-wing conservative blue collar American
WAR DAMN EAGLE!!!!!!
Porting a Hutzl / Stihl 039 cylinder
- Thread starter eudaimonea
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GoBigBlue1984
Right-wing conservative blue collar American
By match the muffler to the exhaust do you mean open the muffler up percentage wise in comparison to what you opened exhaust up horizontally?
He means make your exhaust gasket the same size and shape as your cylinder exhaust flange by trimming the gasket, and then make your muffler opening (exhaust inlet side) the same size and shape as your exhaust gasket.
Remove the deflector from the front of the muffler and add a few holes and/or enlarge the existing ones. If you want it to be louder, drill a couple in the center of the middle recessed area. And before you're done, enlarge the exit hole in the deflector. There are YouTube vids on muffler mods for this saw. Some are mild, some not so much.
Remove the deflector from the front of the muffler and add a few holes and/or enlarge the existing ones. If you want it to be louder, drill a couple in the center of the middle recessed area. And before you're done, enlarge the exit hole in the deflector. There are YouTube vids on muffler mods for this saw. Some are mild, some not so much.
Stihlofadeal64
Addicted to ArboristSite
Eudaimonea, your piston is ready.
Added 2.5 grams of 4047 alloy. As the Huztl pistons are lighter than OEM, the weight should be a wash. Dome 2.5mm high, 26mm wide at base. It clears the plug, I checked it.
Preheated. Welded with AC, 130 amps, 65%EN. 60 Hz.
subbed to this thread. Interested in how the widening of the ports and the popup works out on this build.
GoBigBlue1984
Right-wing conservative blue collar American
So you can open up exhaust flange on the jug in addition to what you remove on the exhaust port so long as not to actually make the exhaust opening any larger? Until I saw the pictures in this thread I had only seen guys widen the exhaust port but not the exhaust flange itself. Makes perfect sense in order to realize gains from work done inside the jug.
Yeah, look at the ported pics vs oem. The flange is almost always opened up slightly. Just gotta be careful not to weaken it by removing too much aluminum.
fearofpavement
Trying them all
The below pics show an 1127 series muffler mod. I have done a bunch of these and the below recipe works well. I do them on a mill but a drill could do it too. The holes are about 3/8". This is an aftermarket Huztl muffler (good quality) and the cover is OEM Stihl.
The two holes in the depressed area go straight through to the exhaust port. All the other ones are baffled. I use a spark screen usually. These are important for keeping stuff out of the engine (mud daubers, etc)
All the 1127 series saws fit the same muffler but there are different amounts of porting from the factory. For instance, if you upgrade an 029 to an 039 it is pretty essential to open the muffler up some or it can't pass enough air to breathe properly. An 039/MS390 has more ports than the 029 or MS290. The below "recipe" works well for all the different engine sizes. You can see on the cover where it is cut back but not so much that the exhaust is going forward. This can catch your wood on fire if you let the exhaust shoot straight out. The baffle in the muffler goes around the depressed area so don't drill too close to the edge of the depression or you'll get into the supporting baffle structure. These baffles have lots of holes so don't need to be messed with in my opinion. One could get by opening up more area around the depression and not drill the center but I think it adds a desirable throaty sound to the saw. The H screw typically needs to be turned out 1/8 turn (additional) if any. Some saws can accommodate this with the limiters in place but most will need to have the limiters trimmed. (NOTE: make sure to thoroughly clean out all shavings before installing the muffler)
The two holes in the depressed area go straight through to the exhaust port. All the other ones are baffled. I use a spark screen usually. These are important for keeping stuff out of the engine (mud daubers, etc)
All the 1127 series saws fit the same muffler but there are different amounts of porting from the factory. For instance, if you upgrade an 029 to an 039 it is pretty essential to open the muffler up some or it can't pass enough air to breathe properly. An 039/MS390 has more ports than the 029 or MS290. The below "recipe" works well for all the different engine sizes. You can see on the cover where it is cut back but not so much that the exhaust is going forward. This can catch your wood on fire if you let the exhaust shoot straight out. The baffle in the muffler goes around the depressed area so don't drill too close to the edge of the depression or you'll get into the supporting baffle structure. These baffles have lots of holes so don't need to be messed with in my opinion. One could get by opening up more area around the depression and not drill the center but I think it adds a desirable throaty sound to the saw. The H screw typically needs to be turned out 1/8 turn (additional) if any. Some saws can accommodate this with the limiters in place but most will need to have the limiters trimmed. (NOTE: make sure to thoroughly clean out all shavings before installing the muffler)
Best post of the year!
drf255
BAD CAD
Bringing the thread back.
Was the saw ever built?
Was the saw ever built?
singletrack100
ArboristSite Operative
eudaimonea
Refurb Advocate
Many thanks to members for keeping this post alive. I do have the saw back together enough to run and test for compression. This is what the porting looks like
Not pretty. I used a nice assorted pack of files I found at a yard sale, some chain files, and sandpaper, along with the carving and engraving dremel kit, along with the carbide dremel tip that looks like a drill bit with a rounded edge. That particular bit took off material really fast both the hard inside coating and the aluminum in the port . I made an effort to make the port "squarish", with hard corners, and then rounded off the inside when I beveled the hard inside coating. Then I smoothed the surfaces with the files and sandpaper. Some of the areas were too gouged to make smooth again, so I ended up with smooth surface with pits and potholes here and there. Shouldnt have been so aggressive. I would have been much better to take off less material and more of a rounder taper from outside to the inside of the intake port.
The exhaust port was opened up in a similar way. I didnt lower the top of the exhaust port or the bottom of the intake port, for fear of affecting the timing. The thinking was that this would affect the timing, but the edges were lowered so the whole inside edge was more or less flat. I did take some material off the integral key of the flywheel, so it can rotate clockwise a few degrees. The thinking was that this would advance the timing. I cleaned everything off and cross-hatched the cylinder wall after beveling the inside edges of the ports.
Looking back I took off too much material across the top of the intake port while I was widening it. My thought was that if I took material from this part of the port, it wouldnt affect timing. The picture on the top shows the piston all the way down. The rings are both peeking through, and I was afraid to start it for fear hot gas would escape through the intake port.
Not pretty. I used a nice assorted pack of files I found at a yard sale, some chain files, and sandpaper, along with the carving and engraving dremel kit, along with the carbide dremel tip that looks like a drill bit with a rounded edge. That particular bit took off material really fast both the hard inside coating and the aluminum in the port . I made an effort to make the port "squarish", with hard corners, and then rounded off the inside when I beveled the hard inside coating. Then I smoothed the surfaces with the files and sandpaper. Some of the areas were too gouged to make smooth again, so I ended up with smooth surface with pits and potholes here and there. Shouldnt have been so aggressive. I would have been much better to take off less material and more of a rounder taper from outside to the inside of the intake port.
The exhaust port was opened up in a similar way. I didnt lower the top of the exhaust port or the bottom of the intake port, for fear of affecting the timing. The thinking was that this would affect the timing, but the edges were lowered so the whole inside edge was more or less flat. I did take some material off the integral key of the flywheel, so it can rotate clockwise a few degrees. The thinking was that this would advance the timing. I cleaned everything off and cross-hatched the cylinder wall after beveling the inside edges of the ports.
Looking back I took off too much material across the top of the intake port while I was widening it. My thought was that if I took material from this part of the port, it wouldnt affect timing. The picture on the top shows the piston all the way down. The rings are both peeking through, and I was afraid to start it for fear hot gas would escape through the intake port.
eudaimonea
Refurb Advocate
Many thanks to drf255 for helping out so much. He did the piston modification for free and I just let this project sit around for so long. He's been really great donating his time and I have no excuse for completely flaking out about this project.
The roof of the exhaust port is way too flat. How much did you raise the intake? How far are the ring locating pins from the edge of the port?
eudaimonea
Refurb Advocate
Got it back together and it started right up!
seems to be running and idling, running with power. I ran it without being put all the way together (drum needle bearing and muffler deflector taking longer than expected) so didn't really test it too much.
But doesn't seem like any hot air is coming out of the intake port! The saw was run without the air filter while I as testing it, and although some gas and air was getting blown across my hand, it wasn't hot.
I tested the compression read 140 psi. I wonder why so low. The piston had a fairly large dome welded on the top of it by drf255, and I used new Caber rings. I wish I new whether I gathe cylinder wall somehow, or if the aftermarket cylinder inherently has too much"play," compared to an OEM cylinder. Or, maybe the compression will r the rings have properly seated nad a decomp plug is installed. The plan is to wait until the plug comes in, and get it into some wood this weekend.
seems to be running and idling, running with power. I ran it without being put all the way together (drum needle bearing and muffler deflector taking longer than expected) so didn't really test it too much.
But doesn't seem like any hot air is coming out of the intake port! The saw was run without the air filter while I as testing it, and although some gas and air was getting blown across my hand, it wasn't hot.
I tested the compression read 140 psi. I wonder why so low. The piston had a fairly large dome welded on the top of it by drf255, and I used new Caber rings. I wish I new whether I gathe cylinder wall somehow, or if the aftermarket cylinder inherently has too much"play," compared to an OEM cylinder. Or, maybe the compression will r the rings have properly seated nad a decomp plug is installed. The plan is to wait until the plug comes in, and get it into some wood this weekend.
GoBigBlue1984
Right-wing conservative blue collar American
Quoting jerry branch here "it's not what you take out of the cylinder but what you put in". How much more is to be gained from adding more flow from the carb to better match your port work? Hey brad how good timing numbers from factory on these saws?
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eudaimonea
Refurb Advocate
I raised the inside of the intake port a LOT, probably did ruin it, but hopefully wont do any damage. I could see myself getting an OEM cylinder and doing this again! Should have measured it before I put it back together, or maybe I can extrapolate the data with a degree wheel
The muffler mod thus far. Not too agressive, although I did open up the muffler intake and so that everything was flush with the outside of the exhaust port. The carb was not modified, and I set the high jet right in the middle of the adjustment (with the tabs intact). Im thinking Ill run it this way during break-in, with the spark arrester screen, and modify it more when Ive put some gas thru it.
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Rx7man
Cattle Rubbing Post
Snelling is right, the exhaust port in particular shouldn't have flat TOP or BOTTOM edges.. You can see the rings flexing out into the cylinder, and that hard edge is going to be very hard on them. Compression at 140 doesn't mean the rings are bad.. my 'wild' Husky 65 has about that, and part of it comes from raising the roof of the exhaust port, giving it less initial volume to compress. Does it still have the base gasket? The squish (especially on a chinese cylinder) may be a little too big.
Why in the world would you expect hot air coming out of the intake port????
drf255
BAD CAD
I'm betting squish awful. Measure it.
I didnt take too much off the flat of the piston on the lathe. You can still see the arrow, so my bet is less than .002. I was careful with that.
With that big dome, you should still be above 200, even with sloppy squish I'd assume.
The Huztl MS250 build I did with a smaller dome than that came out at 220 psi.
Did you raise the exhaust port? That will reduce static compression.
I didnt take too much off the flat of the piston on the lathe. You can still see the arrow, so my bet is less than .002. I was careful with that.
With that big dome, you should still be above 200, even with sloppy squish I'd assume.
The Huztl MS250 build I did with a smaller dome than that came out at 220 psi.
Did you raise the exhaust port? That will reduce static compression.
Paragon Builder
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I could be wrong but it looks like where you opened the muffler will be covered by the deflector when installed. It been a while since I've looked close at one of these though.
Paragon Builder
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No base gasket. It's a clamshell. Hence the popup Al did for him.
