Makita ea7900

[Gabriel1982]

I pry open the crimp and fold it back when I’m done.
On a stock saw you won’t notice a huge difference in power, but I’d split it just to get the guts out so it runs cooler

Wasn't 2 stroke exhaust specially designed for that motor?

 

[Gabriel1982]

Basically he’s saying chainsaws don’t need “back pressure” and the bigger the better (exhaust outlet) lol.

Sooo,on that logic ,why put a muffler anyway?!

 

[Gabriel1982]

I think I'm going to just go with the muffler mod for now. I need to make money with this saw right now, not spend money on it. And I don't really want to be without it for any length of time since I use it every time I go for firewood, which is pretty often. I get splitting the muffler and removing the slr tube, spot welding the flange/spacer back on and then recrimping the two halves back together. Question- is the current exhaust area with the spark arrestor big enough by itself or is there a need to "open up" more of the exterior area on the muffler. I've kinda gathered some guys do this but I have yet to read anything definitive as to how big another opening needs to be, if at all. And if needed how do you do it? How do you know when you are losing too much back pressure? Thank you gentlemen for your advice and help.

Get a spare exhaust to "experiment" with. I can't do this on my Makita EA6100P since it will void the warranty. Maybe in 2 years when I'll be "on my own" with this chainsaw ,and with no warranty

 

[Gabriel1982]

[Not flaming, as many have had poor experiences]
How big of a log? It’s quite possible to get 35-40% faster cut times out of a 7900 or 385 if done properly. A 40 second stock cut would take 24-26 seconds with those gains. Allows you to cut with a 60cc saw rather than 80

Where's the "hurry"? And if it's like that ,one should buy the biggest saw there is and modify port ,etc... That one!

 

[huskihl]

Wasn't 2 stroke exhaust specially designed for that motor?

The first generation just had a birdcage baffle inside to muffle the sound. The later ones have a tube extending into the exhaust port that gets hot to burn off excess hydrocarbons. There’s nothing inside there that’s performance related

 

[huskihl]

Where's the "hurry"? And if it's like that ,one should buy the biggest saw there is and modify port ,etc... That one!

Lots of guys do that, too

 

[Gabriel1982]

The first generation just had a birdcage baffle inside to muffle the sound. The later ones have a tube extending into the exhaust port that gets hot to burn off excess hydrocarbons. There’s nothing inside there that’s performance related

I did remove the exhaust on the 6100 out of curiosity how the cylinder /piston looks(the air filter got loose or I forgot to tighten it well) and I cut some 20" log diameter(50cm) for about 30 minutes... it looked ok... I thought I ruined the whole engine...
now that you explained me how the exhaust works, I wouldn't change/modify anything!
it only "spooges"(black oily thing coming out of exhaust) ,only if it runs for long time at idle. once revved all that motul 2t 800 offroad is gone! exhaust is clean as when I started!

 

[chipper1]

I did remove the exhaust on the 6100 out of curiosity how the cylinder /piston looks(the air filter got loose or I forgot to tighten it well) and I cut some 20" log diameter(50cm) for about 30 minutes... it looked ok... I thought I ruined the whole engine...
now that you explained me how the exhaust works, I wouldn't change/modify anything!
it only "spooges"(black oily thing coming out of exhaust) ,only it it runs for long time at idle. once revved all that motul 2t 800 offroad is gone! exhaust is clean as when I started!

If you damaged the saw from running it with a loose or no air filter, that would be seen on the intake side of the piston.

Where's the "hurry"? And if it's like that ,one should buy the biggest saw there is and modify port ,etc... That one!

Many also want more power out of a lighter powerhead. Porting a 60cc saw will make it run with or close to a 70cc saw, but ots much lighter. The 7900 has a great power to weigh ratio stock, ported they are an awesome powerhouse in a 70cc package and they are 79cc, what's not to like.

 

[Squareground3691]

If you damaged the saw from running it with a loose or no air filter, that would be seen on the intake side of the piston.

Many also want more power out of a lighter powerhead. Porting a 60cc saw will make it run with or close to a 70cc saw, but ots much lighter. The 7900 has a great power to weigh ratio stock, ported they are an awesome powerhouse in a 70cc package and they are 79cc, what's not to like.

Yes sir !!

 

[chipper1]

Yes sir !!

That's a nice one . And a fine example of what I'm saying, no need for a 90cc saw if you have one of those unless you're running longer than a 32 on a normal basi.

 

[Gabriel1982]

If you damaged the saw from running it with a loose or no air filter, that would be seen on the intake side of the piston.

Many also want more power out of a lighter powerhead. Porting a 60cc saw will make it run with or close to a 70cc saw, but ots much lighter. The 7900 has a great power to weigh ratio stock, ported they are an awesome powerhouse in a 70cc package and they are 79cc, what's not to like.

I don't know if I damaged it. Last time I cut with it worked very well on some smaller logs ,to be honest! I just took the exhaust off since it's easier then the carb... Here's some photos taken from the exhaust side... Seems to be some "scores" on the other side 180 degrees from the exhaust side. There's nothing I can do know ....f*** it, I'll be more carefull next time! And this week I'll get to cut some thick logs. If the chainsaw is "dead" it will show up in those,when I bury the blade in them

 

[9050LX]

[ zipping up flameproof suit ]

If you are just looking for a good firewood saw, you really don't need a ported saw. I had my old 385XP ported by a good, reputable saw dude, but the before/after compare wasn't worth the money in my opinion. Yes, the ported saw was a bit faster in the cut. Yes, it was louder. Yes, it pulled a bit stronger. So what? Perhaps the ported saw gained maybe a second or two in bucking a big log. OK...now what? The non-ported saw did everything I asked it to do. The ported saw did it just a little bit faster. I eventually sold the 385XP and bought a new 390XP. When I first bought the 390XP, I thought about having it ported, but then decided against it. The 390 did wake up a bit after it burned enough fuel to "break in" properly.

End of the day -- I just don't see enough "gains" to justify the expense. Saw longevity in ported vs. non-ported will be debated by many with no definitive outcome. I'm at the stage in life where a good stock OEM pro-grade saw is all I need.

JQ

[ Keeps flame-proof suit on ]

Reminds me of dirt bike days where every "Joe Motocross" with a japanese rig (many) would discuss having their cylinders ported.We all would have been better served by extending that effort toward riding skills ,lol.