Exhaust mod on my 670

[Metals406]

I did the mod last night. My camera ran out of batteries, so I wasn't able to continue past cutting the muffler. I did take more pics today, of it finished, and a couple video's.

Factory opening I TIG'd closed...

Position of the muffler as it's mounted, with cutout marked...

You have to remove the bar cover, and inner dog to remove the exhaust... Really not too bad.

Cut out with my Dremel and a cutoff wheel... And the radius's were cut in with a single cut bit in the Dremel.

Different angle...

 

[Metals406]

Here are pics from today, finished deal...


The extension was made from a piece of 1"X2" rec tubing that I cut, and welded back together...

This shows the factory opening TIG'd closed...

<embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i141.photobucket.com/player.swf?file=http://vid141.photobucket.com/albums/r60/IdentityNinjas/Exhaustmod6701-14-09007.flv">

<embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i141.photobucket.com/player.swf?file=http://vid141.photobucket.com/albums/r60/IdentityNinjas/Exhaustmod6701-14-09008.flv">

 

[Metals406]

I am very pleased with the results. I might add that I had to lean the H and L side even more than they were... About a 1/4 to 1/5 turn on the H side, and a 1/2 on the low side... And turned up the idle a bit. Richening the saw only made it not want to run at all. Exhaust port is approximately 125% of port opening at cylinder wall.

In the video, I was blipping to show throttle response... The 670 never had this good of response previous to the mod. And it feels stronger in the cut as well.

It's Muuuuch louder now LOL... I may have to wear ear plugs.

How does the high side sound to you guys in the video? I'd like to take it in to my dealer and have him tack it--out of curiosity.

I'll be adding a screen later to this mod, which I'm sure will restrict it some more.

 

[blsnelling]

You're definately not lean. It's a little richer than I run mine. Yours sure is cutting strong and sounds good too. Nice work. I'm surprised you had to lean out the L. So you're confirming what I've found with having to turn the H in. Like I said, you're definately not lean. You've got a constant 4-stroke at WOT.

 

[Metals406]

You're definately not lean. It's a little richer than I run mine. Yours sure is cutting strong and sounds good too. Nice work. I'm surprised you had to lean out the L. So you're confirming what I've found with having to turn the H in. Like I said, you're definately not lean. You've got a constant 4-stroke at WOT.

I ran it leaner before... And the plug color and top of piston showed it was perfect... But this mod made me a little nervous. Another 32nd of a turn, and it runs real nice... But I'll leave it for now. My mod confirms what you're finding for sure. Without leaning the L side, it wouldn't idle at all coming down from WOT, and would die.

The long slender port opening is supposed to flow better than other port shapes... So I think it was a good decision.

Thanks for responding Brad.

 

[ASEMASTER]

good one

I did mine awhile ago and it looks like a shot gun, man did it wake the saw up it just loves to cut .

 

[Metals406]

I did mine awhile ago and it looks like a shot gun, man did it wake the saw up it just loves to cut .

Right on! What's that stuff on the front of your muffler that looks like epoxy?

 

[rngrchad]

....

Metals,
I kind of brought the post reply over from the DIY muff Mod thread so as to try and not clutter it up too much.....but you were saying your 670
runs a 32" bar and full comp chisel w/ 7 rim sprocket just fine? If my 372 can do that I would be stoked! Rarely do I come across much that needs a 32" but it has happened over the years, and I have my eyes on a few really large sycamores I've been thinking about.

From the looks of everyone elses muffler mods, my single 3/4" pipe seems rather conservative

http://i6.photobucket.com/albums/y201/rngrchad/muffmod1.jpg

 

[Metals406]

Metals,
I kind of brought the post reply over from the DIY muff Mod thread so as to try and not clutter it up too much.....but you were saying your 670
runs a 32" bar and full comp chisel w/ 7 rim sprocket just fine? If my 372 can do that I would be stoked! Rarely do I come across much that needs a 32" but it has happened over the years, and I have my eyes on a few really large sycamores I've been thinking about.

From the looks of everyone elses muffler mods, my single 3/4" pipe seems rather conservative

http://i6.photobucket.com/albums/y201/rngrchad/muffmod1.jpg

I wouldn't say you went conservative, particularly if you left the stock opening in the muffler. Mine looks bigger because I welded the stock one up.

The 372 is 72cc give-or-take right? I see no problem in you running a 32" bar, full comp with a 7-pin. If you think it's too much, switch to full skip. Also keep in mind, that a 24" inch bar can cut into a 48" tree and drop it. You just have to cut in from both sides using a plunge cut. Long bars aren't always necessary for big wood, especially if it's few and far between.

I like a 28" bar because I'm 6'-4"... Not necessarily because I cut huge trees.

 

[JONSEREDFAN6069]

hey metals, here's mine i did a while ago 670 champ thats been ported. cuts like a beast, trust me you will be wearing plugs now. great job on yours that rectangle outlet is sick. wish i wooda thought of that.

 

[bill268xp]

Looks sweet sounds nice . good luck Bill

 

[Metals406]

Great job on those duals! What % of port area did you do?

 

[JONSEREDFAN6069]

it worked out to about 110%, it sure woke it up did that first then ported it after, i was looking at a bigger saw till this now i dont need a bigger one. now i am looking for a good 50cc jonsered, this 026 i have has gotta go.

 

[chainsaw kid]

Nice job Metals....I look forward to doing up my 670 I just got. Just have a few other projects ahead of it as you know.....

Kevin

 

[Metals406]

it worked out to about 110%, it sure woke it up did that first then ported it after, i was looking at a bigger saw till this now i dont need a bigger one. now i am looking for a good 50cc jonsered, this 026 i have has gotta go.

The Dolmar 5100 fits the bill. You could probably find one to cheap, and sell the 026 to help pay for it.

 

[Metals406]

Nice job Metals....I look forward to doing up my 670 I just got. Just have a few other projects ahead of it as you know.....

Kevin

Right on... I suggest a slotted, slender port, it flows awesome.

 

[ASEMASTER]

Right on! What's that stuff on the front of your muffler that looks like epoxy?

This was the first one I did and the muffler was old so I brazed it insted of using the mig, 3/4 conduit .

 

[JONSEREDFAN6069]

Asemaster, I Used 3/4 And Mine Looks'salot Larger Than Yours, I Think Yours Looks Like 1/2".