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Q's on 'proper muffler-modding' (and basic/entry chainsaw mods in-general)

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On 08/02/2020 at 14:18, spudulike said:

I had a 151 in recently, the owner thought is was a bag of poo, it only livened up with the normal Spud recipe which resolved the issues. I tried it before modding and was totally unimpressed as well, afterwards it was like any modded 150 but it was new with one tank through as the owner refused to use it as he owns one of my modified 150s

Matt will know who it was;).....and it wasn't him!



Would love to know if you've got any formal writeups spud?  You seem the go-to guy around here for mods!!

On 10/02/2020 at 16:01, spudulike said:

Your port in the picture - The yellow marks your current exhaust port and it has not been formed correctly. The red marks the area that needs to be bored out - don't forget to bevel the port. 

The cylinders will be cast, machined, plated and then the ports bevelled, I have seen ports like this before and usually just open them up to match the intended shape unless it is to be ported.

You speak about widening ports but haven't mentioned the constraints of the size of bore, ring ends, skirt width, bevelling etc and suggest you understand a bit more before grinding out metal as I have never found a way of sticking the filings back once they hit the bench.


Dodgy Port.jpg

just so I'm crystal clear, I remove the plastic shell to get access to the block, then remove the block's connection to the lower/shaft case area, to get the block/cylinder "alone" to do this w/ carbide bits-then-sanding bits (on die-grinder & dremel) right?  Have never actually touched a port before...  And you're right I have to learn more, **any** resources you can suggest would be majorly appreciated, I'm having a TON of trouble finding good content (am youtubing "chainsaw mod****", "stihl tim*** advance" etc every day's coffee-time for over a week now w/o finding much I didn't already know, at best I can kinda glean info from listening to a couple of youtubers discuss saws they did but they're not for the ignorant ie no explanations of anything just talk as-if you're in the know already)  Would read for days if I'd had some url's for good 'chainsaw modding megathread' type content ;D



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On 08/02/2020 at 05:18, wyk said:

It may be a clamshell with a 90* angled exhaust port, A La Echo and old Macs. Here's an Echo 355t:



This isn't directed at Steve, but the OP:


How a saw behaves with the exhaust modified varies. The 'too much' part is when it starts to blow exhaust on plastics, or just gets too loud. Some exhausts have baffles inside that will go a long ways to defeating any improvements on the external venting if they are not removed. You will almost always need to retune the carburettor.


Always mod the muffler off of the saw. If your piston is at TDC and you pull it over without it igniting any mix, it may actually suck in whatever is in the exhaust instead of blow it out. The last thing you need in a 2t engine is a load of steel shavings.

Would LOVE to know anything you can tell me about (generalities) how a saw behaves / should be approached after modding, whether it's %oil in my fuel, or if H/L/Idle tend to need up or down adjustments, etc (also, should I still treat my OEM-RPM's as gospel for Idle?  Am pretty sure I always respect it for max-RPM but uncertain if Idle-RPM is different for a modded saw, don't wanna be choking-back the saw while tuning with a tach trying to put Idle&Max rpm's to OEM-spec!)


Dumb Q but TDC is when the piston is  on the side where spark-plug is right?  As-in it ignites from the top-mounted spark-plug right?   Wanna ensure I get this right, I've cleaned-out my muff-mod shavings but would still like this type of peace-of-mind!


Agreed on center walls/baffles, I look at entire "through-flow" of a unit for instance the Tanaka tcs33edtp I'm finishing-up right now has two largggge slots carved into the plastic shell right beside the internal air-intake box (there are a couple circular holes drilled elsewhere as well, all have a thin foam sheeting epoxy'ing them in-place, gives more, cleaner air as-needed), then ensured that the opening/volume of the opening of the exhaust-outlet-port on the block was the 'choke-point' from there onward IE I polished the outlet port then widened the muffler's 'intake hole', drilled generously through its center wall & cat, then put multiple holes in its outer wall (two on the back-half of the muffler IE pre-center-baffle!)   


So far as I can tell, that means my 'choke-points' are now the block's intake&exhaust ports IE a porting and timing are the only real power mods left (and maybe a better fuel?  Am using 95oct Husqvarna pre-mix, no additives.....do modded chainsaws ever get to the point they benefit from octane-boosting?)

On 08/02/2020 at 05:40, CutterSy said:


To each their own, if it’s your own saws and you know the risks then fine.
I would never do it on the saw and spend a good amount of time making triple sure there is no swarf left in there! I tend to split the muffler where possible to get better access to the baffle, it’s not always the best option to gut it completely though! Depends if other port work is getting done as to how much to open it up, take it too far and you loose gains.
I use chipper spec ear defenders now!


"Take it too far and you lose gains" -- so you're saying there IS a back-pressure phenomena to be respected here?  Crap, have just been opening stuff w/o regard for back-pressure....Please *plz* tell me anything you're willing to on this subject, I open-up my air-intake and my muffler in the belief it's letting my block operate a bit more powerfully when in a hard cut, would hate tto find some of my mods have been sabotaging me!!

On 08/02/2020 at 05:53, MattyF said:

If there is one saw that benefits from a mod out the box to completely void the warranty it’s the 150 .. the saw is unusable with out it, to be honest I’ve had three unmodded echo 2511’s since saw and I doubt I would buy another 150... any other serious tuning work I give to spud or mild porting myself when replacing pistons etc usually means the saws apart but I don’t do anything drastic !

Does mild porting = a dremel or die-grinder with a sanding-pad (or light/non-aggressive carbide rasps), just opening-up the inlet&outlet ports of the block, no more / no less?

And you mod saws yet you've got 3 un-modded 2511's??  I'd gotten impression that saw was hugely benefitting from mods in fact that's part of why I've got such hope for my generic 25cc is that it's a clone of the 2511 in so many ways, am planning to get a 2nd unit very soon so I can begin more aggressive modding on it to see how far is still safe/reliable so I can then have 2 units that're that way, combined w/ me always having extra, new chains on-hand (as a rule for months now, 2-3 extra chains for all units but at least 1 new/untouched chain :D ) not only as redundancies but for longer days or simply when I want to impress it's nice to have that razor-sharp new-ness which, on most saws but moreso on modded ones, just makes cutting a treat :D

On 08/02/2020 at 10:48, Wonky said:

Here's some  proof,,, and I think reg is a good guy and a laugh. I watch his vids..👍.. ymmv 😉


Ah Reg Coates, guy is amazing I watched every one of his videos at least once when I was starting it was like free online education, sadly in his latest video in the last ~1/3rd he starts talking about how he's going to stop or scale wayyy back, hope he reconsiders!!

On 08/02/2020 at 14:00, spudulike said:

In life there are technicians, blacksmiths and rednecks. I can't charge people to drill holes like that and call it a business so use methods that are engineered, calculated, look nice and work without burning your leg or the saws plastics.

My muffler mods won't deafen the operator but do what they need to, increase the flow without being stupidly loud.

The end result may be similar but it just depends on what the saws owner is looking for.


Well put!!  I'd begun doing "make it professional at all costs" work, now it's "function first, w/ attn paid to form if convenient / if there's time" ROFL but they're my saws they're covered w/ stickers / get beaten up / don't need to be pretty they need to be comfortable & powerful :D


Re *how* to muffler-mod, would really love to hear anything you can offer IE do you use a die-grinder or dremel to make slotttts/slits instead of drilling holes?  Do you pierce the "inside half" of the muffler?  I've found that, even once I've done 1-3 extra holes on the front half of the muffler, and put 1-2 good sized holes in the center wall/baffle, that I still want a hole (or 3!) on the walls of the muffler's inside-half.....I still can't get a straight understanding on whether back-pressure is a consideration here, in fact if I get the time I'm going to benchmark a unit w/ its muffler on & then benchmark with the muffler removed entirely I'll do upward cuts so I'm chipping away from the saw and just use some quick shroud over the exposed exhaust outlet so I can safely do a series of up-cuts on same log w/ and w/o muffler -- my ability to detect subtle differences here sucks though so anything you can share Re back-pressure in a muffler would be greatly appreciated, also what to do after "through-flow" mods (air-intake, muffler mods for much better flow-possibility for block/cylinder), ie should oil% be kept identical?  If I tune by-ear should I just do a re-tune (and, if so, which ways should I be expecting things to go?  I modded a muffler on a 25cc and didn't touch the carb and it's acted fine since, guess it's possible I didn't open it up enough!!)




[PS-- Think I mentioned 'high-heat spraypainting a muffler", at any rate I did use white Krylon high-heat on the Tanaka muffler (matches its shiny new Oregon bar ;D ) and while it was only 1 session I did put a few hours on it and the paint showed zero wear or signs of loss-of-integrity, am now going to get a red high-heat to spray a different unit's muffler IE that 25cc I mentioned modding but not needing to retune its carb, am sure that'll take/want a more extensive modding -- and it's the one with the huge ridge in the exhaust-port that'll be getting ported -- am totally going to get into habit of spraying my mufflers when they're off I know some see it as tacky but I like it 🙂 ]

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56 minutes ago, ArborOdyssey said:

Dumb Q but TDC is when the piston is  on the side where spark-plug is right?

TDC is where the piston is at the top of it's throw and is neither going up nor coming down, it doesn't matter where the spark plug is in relation to it.

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Well that was a lot to digest.
I’m not familiar with the models of saw you are modifying so it’s difficult to visualise, pictures would help.
If you want to dive down the rabbit hole of porting have a read of some of the links in this thread:


Links to porting threads in one place. Please no banter there's plenty of places for that.Feel free to post your favorite thread link. Here are some...

‘How’ to mod a muffler depends on the design and what will fit under/ around covers etc. I usually either add a ‘pipe’ by brazing on a piece of steel tubing, or add a deflector by brazing on a formed piece of sheet steel. I generally either put big holes in or remove the baffle. There are no hard and fast rules, you just need to experiment and see what works for you. I find the more ported cylinders benefit from a more open muffler, but it’s all a balancing act. The more air/fuel that goes in, the more needs to get out (within reason)
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I picked up a bit from Arboristsite, a couple of two stroke tuning books and worked out the rest for myself. As I run a business and do porting, there is a limit to what I will publish whilst I am still running this business as some of the things I do have not been published anywhere on the net so like to keep them private.

As far as muffler mods go, you need to think about what the gasses need to do, where they go and what the muffler needs to do. Back pressure is damn important to expansion chambers and infinitely less so in conventional chainsaw mufflers so you don't need to get hung up on it.

Just study the port openings, how large they can be and the constraints of what you are working with ie ring ends and skirt widths.

It isn't rocket science but it is a dark art!

Edited by spudulike
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Going back to the dodgy port, remove the cylinder, get a carbide burr on the flash and open it up so the port matches the shape of the main cast port shape. DO check that there are no ring ends near the port BEFORE you grind and also check that the piston skirt will cover the port completely on its full travel up and down.

Bevel the port edges after grinding so the ring doesn't snag and then rebuild.

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So much to answer (this site is F'ing tops :D ) but wanted to add a Q on tuning-- have recently gotten impression I shouldn't be aiming for 'true optimal' so much as a touch on the fat side, am getting better tuning by-ear (tach only serves me for making sure max-RPM isn't too high otherwise I find little use which bothers me..), but I hate touching stuff once it's really dialed-in, the L & Idle 'sweet spot' balance is such a PITA on 2 of my older (more cruddy!) pieces of gear....What's 'generic-advice' for carb-tuning after a port-job?  More throughput means more fuel is needed, and I just went and did a (small, thankfully!!) job yesterday where I really pushed my saws (both had had their mufflers just torn open and same w/ air-intakes) and on-job I was thinking they sounded louder but I think they were also getting a bit 'scream-y' (ie lean when pushed) the L and Idle seemed fine but I think they were def lean when run high especially not under-load or out-of-cut....have to turn-out the H screws in both saws, obviously, but uncertain about L (and Idle) ie should I only turn-in H until 'scream' goes away / til I get back to 4-stroking or should I also turn-out my L jet a lil? 
Thanks a ton for any info on this, am OK using the tach although I trust my ear more (which I believe is wrong/opposite ie I should be better at the tach maybe it's because mine's cheapAF? lol!)

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