Husqvarna 445 clammy build

EXHAUST PORT
I was flirting with disaster there... Darn tiny cylinders, specially these deep well clammy saws... Marked it to widen to 27mm but ended up not going all the way there. First 5 second in grinding and I'm thinking I've ruined the cylinder cuz I cut way down on the bottom of the port at the one side... Yikes, hanging a ring was all I could think for a minute or two and I was about to text Jason to take him up on that spare cylinder...
After the panic wore off, I figured I could lower the port to maintain a nice arc on the bottom. This piston / cylinder combo has a ton of room under the port so free porting has plenty of room to spare. Changed to a smaller less aggressive burr to finish up. These pix are still rough and it needs some fine tuning yet.



Miles to go before free porting. This is where the port lands at TDC.


The roof of the exhaust port didn't get touched.


The only concern I have is if I have created a "lazy" spot at the center of the port at BDC where carbon may want to build up. I have my own thoughts on that but I won't bring it up cuz I don't want to turn this thread into another 2 stroke oil debate... I can't remember if my other saws have a little bit at the floor that the piston doesn't drop below or not... Hoping this isn't a problem. As you can see, it still needs some "fixing".

 

Matching the muffler to the exhaust port.
I'm sure many of you know how to do this, but I'll show how I do it for those who just like to see things.

Mount the heat shield to the cylinder and match those.


Then mount the heat shield on the muffler with the gasket.


The muffler on this saw is an open can. I opened the hole under the deflector carefully so the hole is still completely covered by the deflector. I put a slit in the front of the muffler as a second port to double the surface area of the original muffler output hole.

 

Lower Transfers
I didn't want to remove a lot here because I'm trying to keep the crankcase volume as small as possible to keep pressures and velocities in the intake tract up as much as possible. I don't know if this even applies to these chainsaws, but all my experiences tell me that shortening the intake tract adds upper rev power, but doesn't help the torque. So for those two reasons, I didn't hog out the lower entrance to the transfer tunnels. I just rounded the area where the air / gas mix has to make a 180* transition from under the piston coming down and into the transfer tunnel going up. The divider did get edged for flow also. The pictures make it hard to see due to the lighting but the rounding is pretty much a half circle blended to the walls.


In this picture you can also see that the exhaust port roof hasn't really been touched other than the widening.


Still to come:
1. Upper transfer burr removal. I looked for an hour and couldn't find my little set of shaped diamond files that I need for this... I may have to make trip to the store for more... @#$%^&*() As soon as I get back from the store, I'll find them...
2. Chamfering the ports I've worked on... Again, my missing files... They are much gentler on the cylinder plating so I much prefer them.
3. 6* ignition timing advance
4. Light scuff of the plating so the new ring seats.
5. Maybe play with the carburetor.

 

Here's a quick thought from my limited porting experience. While learning about dirt bike 2 strokes they claim that a larger crankcase volume increases bottom end torque. Well that's iirr, its been a few years. They primarily did it with a reed cage spacer.

Does a reed cage motor act differently?

 

A tuned pipe to pull exhaust out and stuff the air / gas mix back in at resonance along with a reed valve to ensure one way flow and no spit-back is a little different animal than a piston ported, limited space can muffler chainsaw.

Weight and space limitations of a saw lead to different methods to enhance performance and also to limit emissions. I'm no expert on it but maybe someone who knows more about it may chime in and help us all learn some more about it. Strato ports on chainsaws were cooked up to limit emissions while still getting the most exhaust evacuation possible. "I think". LOL, I'm kinda reading between the lines on some of this stuff.

I also have an old beater Yamaha Blaster. It has all the "stuff" on it as well, tuned pipe, reed spacer, and boost bottle. The extra few pounds of stuff on that are OK. My arthritic shoulders won't tolerate extra weight on a saw.

I'm thinking that you won't see strato port technology on stuff that has the room and can handle the extra weight required for expansion chamber pipes, reed cages, spacers and bottles. Although in motorsports 4 stroke technology is (has?) taking over cuz they can absorb the extra weight due to the extra power, lots of parts, bigger motor, water cooling, etc...

On firewood day, I'll stick to 6hp, 12lb. saw in the back 40 of my woods rather than a bulky, piped, 12hp 30lb. cookie cutting saw.

 

After thinking about it for a few minutes, I'm thinking that in the dirt world, we were always looking for a wider power band and trying to build torque in the lower rpms. I'm thinking the larger volume / longer intake tract stuff may have been mainly a lower rpm thing which isn't a concern in the saw world of screaming WOT when in wood. Saws are more akin to snowmobiles with torque converters. I know back in the day when I rode sleds, it was either WOT, mashing the brake, or sitting at idle talking to the ladies... Mildly cruising around at low speed wasn't in my wheelhouse or most of the folks I rode with.

I've heard crank stuffers and lower crankcase volumes can be preferable in saws. That was in context of Husqvarna 357 / 359 discussions though so I can't speak for other situations. I'm a novice at this stuff, but trying to learn and pulling in all the info I can recall in trying to make a performance gain on a modest firewood saw. I am putting my thoughts out there and welcome feedback.

 

I'm a nobody when it comes to port work also. I've read lots and ported a couple (2). Both ran noticably better than stock, so maybe i might know something but maybe i don't.

I think you're right about the reed spacer/increased crankcase volume being for low rpm torque. Obviously we're not worried about that in the saw world. Lol. My bad. I've found that once i say the wrong thing and sound like an idiot it really drives that point home/helps my understanding. So thanks for that.

I'm just talking about engine principles in general here but 4 stroke vehicle engines get more torque from longer intake runners. It helps with velocity. Now i think of the transfers in a chainsaw as the "intake runner".

I'm one to read a theory about how it's supposed to work and then try to figure it out/apply it in the real world. Guess I'm just a book nerd.

 

I've read the difference between a Husqvarna 545 and 550 is the 550 has crank stuffers. Supposedly it revs faster and has more hp but isn't as torquey. I've only ran a 550 briefly so no comparison to a 545.

 

No idiots here... just inquisitive novices trying to learn... I find that if I try to put my thoughts into words, I can understand things more clearly, plus I get feedback that helps me stay between the ditches... LOL Lots of like minded folks here that are just trying to make our wood hoarding tasks easier and more fun.

I've done a few saws, but taking baby steps and this is the first strato port saw that I've really dug in deep. The couple other strato saws I worked on I just stuck with widening the exhaust and base gasket deletes, muffler mod, & timing. I'm still trying to figure this stuff out to help some buddies and family cut wood a little faster...

I'm a book nerd too, but I'm trying to get my hands dirty too. It's fun so far...

 

I look forward to seeing how this progresses. Hopefully I can get back to mine eventually.

 

Let me rephrase that; "feel like an idiot." Lol. It's what drives me to learn and do better. (I wish most people worked like that. Lol) I definitely feel ya on putting words to paper helps make it make sense up stairs.

Is that an attempt to confirm that a smaller crankcase is more for hp and a larger for torque?

I really wish treemonkey or someone similar would write a book about chainsaw porting. Best i got is way old screenshots from AS when the main porters over there would talk openly about numbers and theories and such.

 

I'm sure with anything, there is a limit in either direction where performance will be negatively affected. To much volume or not enough.

 

OK, I sat at the bench and went through the cycles several times thinking through the port timing and the strato relationship. After pondering it, I'm thinking a little differently than mentioned before. The intake and strato ports are both open for much of the same time so the few degrees of difference in timing there may make little difference and the relationship has more to do with flow and pressure differences in the two paths into the Crank Case as the piston is going up creating vacuum in the CC. So, I've decided to not alter the strato port timing although I did ease the edges on all parts of the piston just for GPs.

 

Cleaned up the exhaust port and matched the piston to the roof of the port so it would open at the same time all across the arc of the port roof. I just touched the piston with the carbide burr at the deepest parts of the cut and fine tuned it with a tiny file. It doesn't take much.



Doesn't take much on the piston to match that arc.

 

I used a flat diamond file to carefully come into the upper transfer port and clean that ridge of plating that was on the roof of both ports. I took them down flat with the casting so there is no ridge there to cause turbulence drag as the charge enters the combustion chamber. Then I put a small chamfer on the roof and checked the chamfer on the bottoms of the ports as well. These ports aren't very wide and don't need as much chamfer as the much wider exhaust port although the arc on the exhaust port also ensures the ring is safely passed without hanging.
One of the transfer ports on the right. The lighting is difficult but the shiny part is plating that has been filed down flat with the roof of the port and tunnel. The small chamfer was added after this pic.


Exhaust port roof chamfer, not a great pic, but it's there.


I cleaned up the cylinder and ran the 320 grit flapper wheel in it. Since I don't have a good way to hone cylinders, I used some 150 grit emery cloth to hand sand some cross hatching into the cylinder. I don't do much of this but just need to de-glaze the cylinder plating a touch so the ring can seat in better. This is what I've done in the past on saws I had to rebuild and it seems to work OK. Then I used a set of shaped diamond files to ensure a nice chamfer on the ports. I also used a tiny file to smooth over the rough grinding on the lower transfers. I used a tiny flapper wheel inside the exhaust port to smooth it out some. I don't usually go crazy polishing it but I like it smoother than the burr leaves it.

I'll do the ignition timing advance when it's time to put the flywheel on. Very easy to measure the advance as I file with a piston stop in to hold the crankshaft as I tweak it in.

 

Been busy with other stuff and won't be able to work on this saw for a couple days at least. I did have a few minutes and finished up the exhaust port.

Here's a before pic.


After

 

Finally got some time to work on this saw this evening.
Passed the pressure / vac testing with flying colors. It was holding pressure for about a minute when it popped one of the chartreuse plugs clear across the shop...

7psi on vacuum holding fine. Rolled the crank around some to ensure no issues there.

 

Looking good Monte.

 

Got it all back together today and it has some carb issues. I didn't do anything to the carb besides clean it but it's looking like I need to dig into it. Carbs are NOT my forte except for tater chips...

Had to have the low jet out 2 turns to get it to start, but it idles way too high of RPM. Trying to lower the revs just stalls it out. Have to have the high jet out about 3 turns to get it to four stroke when revved up. It takes throttle and cuts OK but is slow going back to idle cuz of the whacky settings. Trying to set the jets anywhere close to normal just stalls the saw like it's starving for fuel. Every once in a while it will settle down and kind of idle OK, but then when I try to adjust the jets correctly, it stalls. The pressure / Vac test was OK during assy. The intake boot where it mates to the carb looks looks good

As I said, I struggle with carbs. I guess I'll tear it down, clean it again, check the lever height, and make sure the membranes and gaskets are all in the right place and order. I ordered an AM carb for it also.



HELP!!!

Suggestions on carbs PLEASE.

 

The carb on that poulan 260 in my thread is what pushed me over the edge lol. I put a completely new walbro diaphragm kit in it and cleaned it. Fuel was running out the throat when priming. Back in, cleaned again, new needle. Lever set with the walbro carb tool. Problem stopped. Saw would run but starving for fuel. Needles way out still starving. Back in again to adjust the lever for more fuel... running out the carb throat again. Nephew happened to be at the house and I gave it to him right then and there. I'm tired of that pos. I have another carb I'm giving him to try that came off another running poulan but the linkages need swapped out.