muff mod...tried something different

[hvy048]

Hi Guys. I was looking for a way to mod a muffler without welding or brazing 'cause just everybody doesn't have that option. Second, I wanted to keep the cost down. After reading much of the info on AS, I didn't want to just drill holes, because that puts a lot of heat directly in front of the muffler, bad for obvious reasons. I had an old beat up cover so I started playing.
This is what I came up with:
I used a dremel cutoff wheel to make slices across the raised "ridges" about 3/8: from the ends. I got 10 holes, together with the existing port I figured that 1/4" holes would get me pretty close to the 85% I was looking for. The theory was to reverse the dimple at the ends to make a sort of louvered effect to direct the exhaust off to the sides as much as possible. I ground down an old screwdriver to do the job. To keep it legal by big brother's standards, I formed some .0229" screen and sandwiched it between the cover and muffler body. I figured that much area should not affect flow much. The restriction factor of the stock screen over the stock port was unknown, so I disregarded it for now. I checked rpms with a DTI-20K tach. Before swapping the cover my 440 peaked at 12,200.....after installing the modded cover it peaked at 13,800 (round numbers) without carb adjustment. I guess I expected more of a difference. Since this was my first attempt, I don't know if this was a success or not. Your thoughts and suggestions would be most appreciated. Please.....Tell me what you think.
hvy048

 

[Haywire Haywood]

Since you've done the reading I'm going to assume that you know not to leave the carb unadjusted unless you really don't like your saw, so I won't mention it here.

I think the goal is not for more RPMs, but rather more power at stock or near-stock RPMs.

Ian

 

[timberwolf]

Sounds like it was a bit rich to start, so might have worked out, but not bat for the HS, but I would think you would need to richen the LS up a little.

 

[somebum]

i may just have to try this on the 034

 

[hvy048]

carb needs adjusting for sure........

I just mentioned that to give you guys the RPM differences before any adjustments were made. I agree it was too rich before I did the mod. I just got the tach yesterday, and that shows that my ear is not as good as it should be.....so I erred on the side of caution.
My biggest concern was the possibility of cracking. I guess a guy could, and maybe should use a smaller screwdriver, maybe a 3/16" and then drill or grind the holes a bit bigger to eliminate any stresses that could develop along the sides. The holes did turn out pretty good tho....time will tell.
Thanks for your comments!
hvy048

 

[tek9tim]

Good thinking, certainly different. Seems like it'd look pretty cool before the saw's warmed up, and it's spewing smoke.

 

[Lakeside53]

Looks good. Just be careful to watch out for hot gases being directed at any plastic parts like the brake handle. The heat can cut though them real quick.

How does it sound?

 

[timberwolf]

I don't think craking will be a problem, muffler covers seam to be decent metal and I have not had any cracking problems.

 

[hvy048]

Thanks Guys!!

You guys' approval means a lot! It looks like all is clear of the hot exhaust, the smoke on startup diffuses in about a 45 deg angle each way. We had a light snowfall last nite and the exhaust showed up really good this morning. Something beautiful about that blue haze against the pure white background!.....oops, going off the deep end there.....it's a chainsaw thing! The saw is louder for sure, but lacks the sharp crackle that a larger single port gives. That could be good or bad depending on your point of view......I like the sound it makes! Timberwolf.... I hadn't thought of the LS needing adjusting too...( I should have)...thanks for waking me up on that one! I did notice that it idled faster, so maybe it would have dawned on me once I started using it. With any luck tomorrow I will get a chance to do some cutting to test it there. If it works like it should, the 036 is next!
I have heard some of you talk about tuning the carb while in a cut. Would somebody explain what the procedure is for that?
Happy sawing!
hvy048

 

[ChuckinOhio]

Thats a great idea, way to use the old bean!!

Chuck

 

[CaseyForrest]

Just watch out for "suck back."

Its a saw killer.

 

[ChuckinOhio]

you beat me to it

I thought of it too late.

Suckback Bwahahahahaha.

Chuck

 

[hvy048]

suckback sucks!

You raise another good point!
I am hoping the smallish .0229 screen opening will guard against suckback as much as possible. If any of you fellas have a surefire cure, I would really like to hear it. I did take pains to clean the inside of the muffler body, and made sure there were no loose pieces on the screen material before putting it together. That's about all I know how to do about it.
hvy048

 

[kevinj]

You raise another good point!
I am hoping the smallish .0229 screen opening will guard against suckback as much as possible. If any of you fellas have a surefire cure, I would really like to hear it. I did take pains to clean the inside of the muffler body, and made sure there were no loose pieces on the screen material before putting it together. That's about all I know how to do about it.
hvy048

You'll need a suckback preventer.

Do a search on suckback prevention. :smoking:


I think Stihl makes a suckback prevention kit.
I'll bet Lakeside can give you the part #.

 

[BIG JAKE]

Just watch out for "suck back."

Its a saw killer.

Who was that guy on ebay? Craxmon? Crackman? :hmm3grin2orange:

Yep-the dreaded "suck back". I saw those mufflers listed the other day.

Nice job on the muffler Hvy! :rockn:

 

[hvy048]

There's the answer!

Ya got me!...caught me bein' all serious and stuff!
I am thinking that I should scrap my muffler and buy one of those! I think that "surefire suck back preventer" might just do the trick!
hvy048

 

[RaisedByWolves]

I think you had a good idea and did a good job executing it.



Nice neat work!

 

[hvy048]

Thanks to all!

I got some great feedback, and a couple of jokers out of this. I had a chance to tune the carb and cut some wood today. I have to say that imho the mod had a good effect on the 440. I was bucking up some 18-20" white fir and the difference was noticeable right off. Sue says..."Looks like you're cutting butter!"
I found I could lean into it a bit harder and it held the rpms real well.
The fresh paint on the muff cover sent off some strong odors that scared me until I figured out what it was.
The only thing I didn't feel comfortable about, was the low speed adjust. It was only about 1/8 turn off the seat when I finished the tuning. Does that sound right? Because the saw is new, I left it a bit on the rich side on the high end, max rpm set at 12k. After a few tanks I'll set it up a bit.
Over all I am as happy as a skeeter in a blood bank!
That 036 is starting to feel the need..........
hvy048