Yet Another 42cc Poulan Porting Thread

[Chris-PA]

Thanks for posting this ....... awesome work on what most consider "throw away" saws.
I have a few and they are pretty reliable !
What program did you use for the port timing charts ?

Thanks! They were drawn in AutoSketch, which is a simple 2D CAD package I've used for years.

 

[FlyingDutchman]

Chris, I have a similar Sears/Poulan saw. Making a kickass limbing/junk lumber shredding/fence line clearing saw out of it running a 14" bar because chains are cheap and less bar really makes this saw rip. Made a full skip chain by hitting nails breaking off cutters lol. Ive been reading on porting. Last night cleaned up the exhaust port and heat sleeve which was really carboned up. Saw immediately idled better.

Did you pull the heat sleeve out of the exhaust port? Why didn't you attack that lower lip on the exhaust port? Seems like that lower lip is hogged out it would really open it up. After looking at the pic it just looks like you cleaned up the casting and pulled the sleeve.

When you modded the muffler, how did you modify the Baffle? I was thinking about just drilling out the lower dimple on the muffler and pointing the opening on the baffle down towards it instead of upwards like stock and opening the top of the muffler like you did.

How critical is the larger carb? Will the smaller carb run out of adjustment after mods are done? Or will it just be a choke point?

Thanks for making this thread with the great pics and video!

 

[Chris-PA]

Chris, I have a similar Sears/Poulan saw. Making a kickass limbing/junk lumber shredding/fence line clearing saw out of it running a 14" bar because chains are cheap and less bar really makes this saw rip. Made a full skip chain by hitting nails breaking off cutters lol. Ive been reading on porting. Last night cleaned up the exhaust port and heat sleeve which was really carboned up. Saw immediately idled better.

Did you pull the heat sleeve out of the exhaust port? Why didn't you attack that lower lip on the exhaust port? Seems like that lower lip is hogged out it would really open it up. After looking at the pic it just looks like you cleaned up the casting and pulled the sleeve.

When you modded the muffler, how did you modify the Baffle? I was thinking about just drilling out the lower dimple on the muffler and pointing the opening on the baffle down towards it instead of upwards like stock and opening the top of the muffler like you did.

How critical is the larger carb? Will the smaller carb run out of adjustment after mods are done? Or will it just be a choke point?

Thanks for making this thread with the great pics and video!

The exhaust work I did here was limited to widening the port, and that meant the sleeve wouldn't fit anymore. I did not raise the port as I was trying not to reduce cylinder pressure given the already large squish distance. Dropping the lower port edge does not really change the timing, and on these you WILL free port it if you do that. The lower edge of the piston will open into the exhaust port. The remaining step is not really a problem for flow as it is opening to a bigger area/volume.

If you look at the picture of the muffler, I've cut away a whole section of the bottom of the baffle. Here is another shot of a baffle where I just drilled the holes and one with the bottom cut out:

The particular shield I used on this saw works the best, as it allows you to cut a big hole at the back upper corner but still directs the exhaust forward and does not melt the chain brake handle. You can do other things though, like these examples:

I'm a little conservative in muffler outlet size, and my baffle opening is on the bottom in an attempt to make the exhaust gas pass through the lower portion of the muffler. I try for a long path length but low restriction.

I don't think changing the carb is required. The stock 28/64 is fine and I'm not sure I gained much with the 34/64.

 

[heyduke]

The exhaust work I did here was limited to widening the port, and that meant the sleeve wouldn't fit anymore. I did not raise the port as I was trying not to reduce cylinder pressure given the already large squish distance. Dropping the lower port edge does not really change the timing, and on these you WILL free port it if you do that. The lower edge of the piston will open into the exhaust port. The remaining step is not really a problem for flow as it is opening to a bigger area/volume.

If you look at the picture of the muffler, I've cut away a whole section of the bottom of the baffle. Here is another shot of a baffle where I just drilled the holes and one with the bottom cut out:
View attachment 393359
The particular shield I used on this saw works the best, as it allows you to cut a big hole at the back upper corner but still directs the exhaust forward and does not melt the chain brake handle. You can do other things though, like these examples:
View attachment 393360
I'm a little conservative in muffler outlet size, and my baffle opening is on the bottom in an attempt to make the exhaust gas pass through the lower portion of the muffler. I try for a long path length but low restriction.

I don't think changing the carb is required. The stock 28/64 is fine and I'm not sure I gained much with the 34/64.

chris-

that muffler is a different design from the current 42cc poulans. it looks less restrictive to me. i bought a new strato to serve as my winter lab rat. it ran poorly out of the box, wouldn't hit 10k rpm, wimpy power, really poor throttle response. after i finally got a carb tuning wrench i enriched it, h & l, and that helped but it still wasn't right. took a look at the muffler. it was really restricted, the worst i've ever seen. i'll post some fotos of how i corrected that later. after the muffler was opened a little, things really improved and it became much easier to find the sweet spot in the carb. now looking at your earlier muffs i'm thinking i might order one and try it. they look like they'll bolt on. regarding the stock tuning of the carb, i live at 6000' and should have needed to lean it out, wierd.

 

[Chris-PA]

chris-

that muffler is a different design from the current 42cc poulans. it looks less restrictive to me. i bought a new strato to serve as my winter lab rat. it ran poorly out of the box, wouldn't hit 10k rpm, wimpy power, really poor throttle response. after i finally got a carb tuning wrench i enriched it, h & l, and that helped but it still wasn't right. took a look at the muffler. it was really restricted, the worst i've ever seen. i'll post some fotos of how i corrected that later. after the muffler was opened a little, things really improved and it became much easier to find the sweet spot in the carb. now looking at your earlier muffs i'm thinking i might order one and try it. they look like they'll bolt on. regarding the stock tuning of the carb, i live at 6000' and should have needed to lean it out, wierd.

Near as I can tell there were 3 generations of that muffler - the early ones like I have (which are common as dirt), the 3rd one you have which I have not seen in person, and the 2nd which was a cat muffler they used right before they switched to strato. The cat mufflers are the worst, but have that nice shield/deflector I used on this saw.

I believe the 3rd generation has a front outlet, which might be required with the later brake handles that have 2 supports. The first 2 generations have outlets at the top rear on the clutch side - hence the need for the deflector.

 

[heyduke]

Near as I can tell there were 3 generations of that muffler - the early ones like I have (which are common as dirt), the 3rd one you have which I have not seen in person, and the 2nd which was a cat muffler they used right before they switched to strato. The cat mufflers are the worst, but have that nice shield/deflector I used on this saw.

I believe the 3rd generation has a front outlet, which might be required with the later brake handles that have 2 supports. The first 2 generations have outlets at the top rear on the clutch side - hence the need for the deflector.

yes, i saw that the outlets were on the rear, unusual. they probably wouldn't work unless you welded them shut and made new outlets on the front or right side. thanks for the expertise. the 3g's do indeed have front outlet, and behind it two microscopic slots that are the actual muffler chamber outlets. this bad situation is made worse by the front outlet plate that has a very small clearance between it and the muffler chamber. i'll post pictures of my field mod after it's warm enuff to toddle down to the shop with a camera.

 

[Chris-PA]

yes, i saw that the outlets were on the rear, unusual.

It did seem strange at first, but it allows you to make a quite free flowing muffler that is not very loud.

 

[heyduke]

It did seem strange at first, but it allows you to make a quite free flowing muffler that is not very loud.

right, however the newer mufflers are quite restricted. the clearance between the muffler body and the front plate is ridiculous. the spark arrester is in there too and the flow is so bad that the screen was starting to clog up after less than a quarter tank of fuel. here's some photos of what i did. before the field mod carb adjustments had little effect. it ran poorly no matter what i did. after the mod i was able to get almost 12k rpm with a a little four stroking and fairly good throttle response.

here are the two slots that are the total outlet from the muffler. i doubled their width.



i was tempted to loose the front plate but that's not smart in the dry conditions around here.. so i made a 1/16" spacer:



here's how it fits into the muffler:



here with the front plate and spark arrester mounted, i like the fact that it looks stock.



not shown was a washer that fits under the front plate it's made of the same material as the spacer and is needed so the front plate isn't bent when you tighten the mounting nut.

 

[Chris-PA]

right, however the newer mufflers are quite restricted. the clearance between the muffler body and the front plate is ridiculous. the spark arrester is in there too and the flow is so bad that the screen was starting to clog up after less than a quarter tank of fuel. here's some photos of what i did. before the field mod carb adjustments had little effect. it ran poorly no matter what i did. after the mod i was able to get almost 12k rpm with a a little four stroking and fairly good throttle response.

here are the two slots that are the total outlet from the muffler. i doubled their width.

View attachment 393686

i was tempted to loose the front plate but that's not smart in the dry conditions around here.. so i made a 1/16" spacer:

View attachment 393687

here's how it fits into the muffler:

View attachment 393690

here with the front plate and spark arrester mounted, i like the fact that it looks stock.

View attachment 393692

not shown was a washer that fits under the front plate it's made of the same material as the spacer and is needed so the front plate isn't bent when you tighten the mounting nut.

Nice job - I think I would be tempted to see if the older muffler would fit using one of the second generation shields. It might clear the brake arm.

 

[heyduke]

Nice job - I think I would be tempted to see if the older muffler would fit using one of the second generation shields. It might clear the brake arm.

i haven't been able to find a model number to do a parts search. all the pp4218's i looked on partstree used the same muffler, same with 4018's and even wildthings. maybe you could give me a sears or poulan model number. the stock muffler is only $15 plus shipping. another alternative would be a second port in the body below the existing port.

 

[Chris-PA]

i haven't been able to find a model number to do a parts search. all the pp4218's i looked on partstree used the same muffler, same with 4018's and even wildthings. maybe you could give me a sears or poulan model number. the stock muffler is only $15 plus shipping. another alternative would be a second port in the body below the existing port.

The number for the older muffler assembly I have is 530047207. A lot of them show up on eBay with no number though. They are pretty easy to recognize, as they are two piece and black as opposed to silver and they have a shape that is distinctive from the mufflers from other saws.

 

[heyduke]

The number for the older muffler assembly I have is 530047207. A lot of them show up on eBay with no number though. They are pretty easy to recognize, as they are two piece and black as opposed to silver and they have a shape that is distinctive from the mufflers from other saws.

looks like the same muffler as a 2050.

 

[Moparmyway]

I usually take the tubes out as well

 

[FlyingDutchman]

Chris my particular muffler shield has just a small opening (not the one with a converter and the big opening). Any suggestions for making a muffler mod work on the small shield exhaust or is getting one of these big opening shields?

Currently on eBay for $6. Thanks!

 

[Chris-PA]

Chris my particular muffler shield has just a small opening (not the one with a converter and the big opening). Any suggestions for making a muffler mod work on the small shield exhaust or is getting one of these big opening shields?

Currently on eBay for $6. Thanks!

Yeah, I did several before I got the deeper deflector you show there. These are some modified outlets, one with an added forward gill that worked quite well:

Then I bent the rear defector outward just a little:

It's a decent outlet area, and not too loud either. Needed a bit of shield for this one:

 

[heyduke]

Chris my particular muffler shield has just a small opening (not the one with a converter and the big opening). Any suggestions for making a muffler mod work on the small shield exhaust or is getting one of these big opening shields?

Currently on eBay for $6. Thanks!

dutchman-

can you post the search you used to find this muffler shield? thanks.

 

[Milkman31]

Now I won't to go play with the 295!

 

[FlyingDutchman]

Just searched poulan muffler on eBay till I found one with the right shield. I don't like posting links to auctions because how often you find threads 5-6 years later and no idea what's going on cause the auction ended

 

[heyduke]

Just searched poulan muffler on eBay till I found one with the right shield. I don't like posting links to auctions because how often you find threads 5-6 years later and no idea what's going on cause the auction ended

dutchman-

thanks, i didn't want a link, frowned upon on this site. that's why i asked about your search string. i like the look of that muffler and would like to find one.

 

[Chris-PA]

dutchman-

thanks, i didn't want a link, frowned upon on this site. that's why i asked about your search string. i like the look of that muffler and would like to find one.

The muffler itself is an impossibly choked up cat muffler - I've bought a couple of them just to get the shield though.