Saw Modz

Jackjcc · Nov 3, 2015

I have been big into saw modification for a few years and have recently gotten into actually being an arborist. I got on this site to try to learn and thing or two about climbing. It's nice to see a chainsaw section to this site. When I started working for a tree care company I figured based on their saws that saw modz weren't common in the industry. If any body wants to mod their saw, feel free to post up questions and I will do my best to give an impartial unbiased answer or link to the experts at my original internet saw home arboristsite.com. everyone should get on there if they have a question about a saw, over there it's been asked or been explained for every saw available.

I know I am new to the forum, but saws were my original interest in arboriculture.

Worthaug · Nov 7, 2015

@Jackjcc, welcome to the Buzz! If love to answer your climbing questions in return for some saw mod info! I have a husqy 338 that I'd love to make a little ripper...

Reed Wortley
CTSP #01739
ISA CA #SO-6953A

fall_risk · Nov 8, 2015

seconded

Sent from my XT1080 using Tapatalk

Jackjcc · Nov 9, 2015

The 2 cycle engine works like an air pump. The more air volume going through the saw, the more fuel available to combust and therefore increased RPMs and power.

So, by increasing the size of the exhaust outlet you get better flow through the engine. This does decrease fuel economy, but most people aren't very concerned with that. It is also possible to open it too much, but we won't have to worry about that. Another added benefit is cooler operation, the exhaust carries away heat and slow exhaust removal transfers more heat to components.

There are two types of muffler that came on the 338. Worthaug, can you post a pic of your saw with the exhaust cover plastic off?

Worthaug · Nov 9, 2015

It's this one @Jackjcc

Reed Wortley
CTSP #01739
ISA CA #SO-6953A

Jackjcc · Nov 10, 2015

looks like you've already taken out the spark screen? I can't really see if the screen is in there. You have two options, grind the opening under the deflector which points up or creating a new hole. My vote would be for a new hole, something like what snellerized 201t's have.

With all the dings on that muffler I wonder if you use the plastic cover?

If you do use it then when you drill a new hole through the muffler, you will have to make a new exit by trimming away a section or two of the plastic. 5/8th's would be a safe choice, that would probably double your exhaust size, not sure exactly what size hole is under that deflector.

The next extremely important step is to modify the carb. There are plastic limiters over the adjustment screws, if you have adjusted the carb then you have probably realized there is a limit to the adjustment. A good thing to try out is to adjust the carb with the limiters on before modifying so you get a feel for adjustments without having to worry about over doing it.

The limiters fit over the splined carb adjustment screws and look like this:

What you want to do is remove the parts sticking out at the top, while leaving the rest intact. Removing them can be slightly tricking, analyze how they are stuck on, and most likely you can use a drywall screw to gently screw into the top and pull out. After the tabs at the top have been removed you can push the "limitlesslers" back on the splined carb adjusters to help get a screwdriver in for adjustment.

How familiar are you with adjusting carbs? I think I will stop here let me know if you are following or have questions.

If you are not familiar with adjusting the carb, my favorite explanation can be found here:
http://store.chainsawr.com/blogs/tu...djustment-and-tuning-of-a-chainsaw-carburetor
This is also a great place to find parts for saws, I have sent him emails with odd parts not listed and been amazed at how quickly he has found them. Great resource to have when looking for parts.

chiselbit · Nov 15, 2015

Jackjcc said:
I have been big into saw modification for a few years and have recently gotten into actually being an arborist. I got on this site to try to learn and thing or two about climbing. It's nice to see a chainsaw section to this site. When I started working for a tree care company I figured based on their saws that saw modz weren't common in the industry. If any body wants to mod their saw, feel free to post up questions and I will do my best to give an impartial unbiased answer or link to the experts at my original internet saw home arboristsite.com. everyone should get on there if they have a question about a saw, over there it's been asked or been explained for every saw available.

I know I am new to the forum, but saws were my original interest in arboriculture.

Hi jack, what happens when you open up the intake and exhaust on a computer controlled saw? Like a 661 for example. I am less than impressed with mine. I have one of the last 660's and put the stihl dual port muffler and a max flow air cleaner on it and it made a nice noticeable difference in performance. But this new 661 could use some improvement. It is my understanding that max flow does not have a filter kit for the 661 yet. I'm thinking I can just put the foam filter over the useless stock filter and add a port to the muff. But wasn't sure if this would mess with the computers parameters. I'm cutting timber in a burn area and the stock air filter gets plugged up fast, plus it's letting a lot of stuff get past.

Jackjcc · Nov 17, 2015

The stock filters are great on the new mtronics. All the adjustments you make will be accounted for automatically by the "computer." If you open the muffler and increase airflow, the saw will compensate.

There is some speculation that the 661 may be limited for the few half dozen tanks of fuel. A lot of people have reported that its like a switch is flipped and the saw seriously opens up. So if your 661 is still new, you need to get 10 tanks of fuel through it before you need to be concerned.

chiselbit · Nov 17, 2015

Jackjcc said:
The stock filters are great on the new mtronics. All the adjustments you make will be accounted for automatically by the "computer." If you open the muffler and increase airflow, the saw will compensate.

There is some speculation that the 661 may be limited for the few half dozen tanks of fuel. A lot of people have reported that its like a switch is flipped and the saw seriously opens up. So if your 661 is still new, you need to get 10 tanks of fuel through it before you need to be concerned.

Thanks for the info jack. I'll go ahead with the mods. I have ran about 3 gallons of fuel thru it, don't know how many tanks that is. And the stock filter just isn't up to the harsh conditions of cutting trees in a burn. It plugs up too fast. I appreciate your reply. Thank you.

Jackjcc · Nov 17, 2015

Yeah that's more than 10 tanks. Did you experience anything like I mentioned? Where the saw just woke up? I've heard zero complaints about the 661 lacking power.

chiselbit · Nov 21, 2015

Jackjcc said:
Yeah that's more than 10 tanks. Did you experience anything like I mentioned? Where the saw just woke up? I've heard zero complaints about the 661 lacking power.

Ok, I opened up the exhaust and put a max flow foam filter over the top of the stock filter, and removed most of the air filter cover. Keeping just enough to lock down the filter. Ala green weenie style. I work a timber falling job on weekends so tomorrow will be the real test but when test running it today in the yard it came alive.

chiselbit · Nov 21, 2015

chiselbit said:
Ok, I opened up the exhaust and put a max flow foam filter over the top of the stock filter, and removed most of the air filter cover. Keeping just enough to lock down the filter. Ala green weenie style. I work a timber falling job on weekends so tomorrow will be the real test but when test running it today in the yard it came alive.

Jackjcc · Nov 21, 2015

Nice work on that! You will get a good boost from the increased flow. I'm not a fan of removing the filter cover like that, pretty common on mild race saws, but not very common for work saws. Hopefully you'll get a good seal and it won't flex much if you push on it from the side.

chiselbit · Nov 22, 2015

Jackjcc said:
Nice work on that! You will get a good boost from the increased flow. I'm not a fan of removing the filter cover like that, pretty common on mild race saws, but not very common for work saws. Hopefully you'll get a good seal and it won't flex much if you push on it from the side.

It's got the stock filter under the foam so it's a solid lock. seems to be fine

arboristowen · Nov 23, 2015

hi jack! what size of hole do i need to drill in my stihl ms 150t to get a bit more jam?

Worthaug · Nov 30, 2015

Hey @Jackjcc, this particular 338 has problems with a self adjusting T screw (idle adjustment). When I mod the muffler and adjust (modify) the high and low screws, will this still be an issue? Does the T screw need to be messed with too?
Thanks in advance.

Reed Wortley
CTSP #01739
ISA CA #SO-6953A

Jackjcc · Dec 2, 2015

Most likely, I'd try blue lock tight. Just clean the screw with carb cleaner to get any oil off and put a dab on one side of the screws threads. That should keep it snug and still allow you to turn it. Not sure if gas will break it down over time though.