Anyone here really know about Stihl chainsaws (larger saws) ???

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Back pressure helps with valve cooling and if you remove back pressure you'll cook the heads , take the stock exhaust off a harley and put straight pipes on it and you have to add torque cones into the exhaust tubes or it won't run worth sh*t , on a car all you need to do is increase fuel your really dealing with velocity and the small amount of reduced pressure when the valve is closed would help clear the exhaust gases when it opens , if you take away some sort of exhaust you lose velocity and thats why your civic didn't get any benefit

This tread has taken a turn from the original posters question. I do not know where to go with this as a result. Perhaps someone can move it. Grump, there are many intricacies to the internal combustion engine. When you put pipes on a motor cycle or a car, you've messed with the factory settings of its fuel/air ratio. Because you've freed up the exhaust, you've allowed more air to come in on the intake side. Now if you don't do one of two things (for a cycle anyway), you are going to run lean and lean ( more air) is going to produce higher combustion temps. You need to either induce reversion (torque cones) or rejet the carbs for more fuel to keep the original air/fuel ratio to keep things cooler. Reversion cones can still make for a hot engine but at least you've created a 180 degree pulse change and maybe balanced out the system. This method is hit or miss depending on the engine and the drag pipe manufacturer. Having pipe connectors on the drag pipes can also work. If eventually you do nothing to compensate for the disturbance in air/fuel delivery, you are going to create hot spots on the valves and eventually lead to valve failure. This problem is not so much due to back pressure as it is more to do with exhaust increased velocities altering fuel/air ratios.
When I altered my V twin by putting pipes on, I had to rejet the carbs 3 times before I got it right as pipes were getting yellow from the excess heat.

 

[Grumpy Old Man]

This tread has taken a turn from the original posters question. I do not know where to go with this as a result. Perhaps someone can move it. Grump, there are many intricacies to the internal combustion engine. When you put pipes on a motor cycle or a car, you've messed with the factory settings of its fuel/air ratio. Because you've freed up the exhaust, you've allowed more air to come in on the intake side. Now if you don't do one of two things (for a cycle anyway), you are going to run lean and lean ( more air) is going to produce higher combustion temps. You need to either induce reversion (torque cones) or rejet the carbs for more fuel to keep the original air/fuel ratio to keep things cooler. Reversion cones can still make for a hot engine but at least you've created a 180 degree pulse change and maybe balanced out the system. This method is hit or miss depending on the engine and the drag pipe manufacturer. Having pipe connectors on the drag pipes can also work. If eventually you do nothing to compensate for the disturbance in air/fuel delivery, you are going to create hot spots on the valves and eventually lead to valve failure. This problem is not so much due to back pressure as it is more to do with exhaust increased velocities altering fuel/air ratios.
When I altered my V twin by putting pipes on, I had to rejet the carbs 3 times before I got it right as pipes were getting yellow from the excess heat.

Isn't that what I just said ? ,I'm NOT an advocate of modifying 2 stroke exhausts

 

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Isn't that what I just said ? ,I'm NOT an advocate of modifying 2 stroke exhausts

Huh? My thread had nothing to do with exhaust modification of 2 stroke engines. My thread was about why 4 stroke engines do not have the problems people think they have because of no back pressure.

 

[Grumpy Old Man]

Huh? My thread had nothing to do with exhaust modification of 2 stroke engines. My thread was about why 4 stroke engines do not have the problems people think they have because of no back pressure.

On the chainsaw level i do not advise the general user to modify the exhaust . On the Harley level we said the same thing ,Ive built more than a few big inch pro street bikes !

 

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On the chainsaw level i do not advise the general user to modify the exhaust . On the Harley level we said the same thing ,Ive built more than a few big inch pro street bikes !

I do not think we said the same thing. Personally, I would not rely on a torque cone. I think of it as a bandage for a larger problem and a bandage that may or may not work. Engine can still run hot with a reversion cone. You've built bikes and I've built high performance engines. All I'm saying is back pressure needed on a 4 cycle engine is a myth and said how and why its misconstrued. I'm good with it all.

 

[DieselnHooters]

On the chainsaw level i do not advise the general user to modify the exhaust . On the Harley level we said the same thing ,Ive built more than a few big inch pro street bikes !

unless you have clipped a few trees with your street bike you are on the wrong thread

 

[SpringHollow]

I have a Stihl 180, 260 Pro, 361, and a 660. All great saws when used for the correct job. Whichever one i happen to be using is my favorite saw at the moment. I do not really need the 260 but it was the first of the newer saws. Traded in my old 20 year + Stihl saws over a 1 year period With the 2 trades, I ended up paying well less that $1000 total for all 4 saws. Before buying the trades, he tore them apart and said they had been well maintained, that they were pristine inside and he wanted them for parts, not even as a whole saw. Said he could make more out of fixing customers saws with them than he could selling them whole.

Ken

Ken

 

[20 20]

Been using chainsaws all of my life and never did any kind of "muffler mod". Occasionally a muffler would loosen or fall off and I would put it back on. When you have to hear a screaming saw hour after hour, day after day you tend not to do anything to make them any louder. At least I didn't, nor do I remember any professional loggers doing so. My advice would be to get a saw of the right size and learn to sharpen it well and maintain the bar. As long as the saw is running well, sharpening the chain properly and keeping the rakers at the proper height is, in my opinion, the most important consideration in saw performance. The difference between avarage chainsaw men and good ones is in bar/chain maintenance skills. My opinion.

I have also been running saws for over 35 years, own a mill so I do have a small idea about the equipment I use. Yesteryears saws did not have all the restrictions of todays saws, that is my reason for my mods. As I pointed out I did not do the mod for a huge gain in power I did it for cooler running and better air flow. I know more loggers that have done proper muffler mods then not, for the same reason as I mentioned. I also stated get a saw that is made for the work intended, DO NOT do a muffler mod to try and make a 30cc engine do the work of an 80cc engine this would be silly. I just mentioned the muffler mod because I believe it is a good idea. I have thousands of $$$'s in my saws and I want them to last as long as possible. I also wrote that the noise level on my saws did not change all that much. One poster mentioned how his friend had done a mod and it screamed, I believe the friend just hacked his muffler up, heard loud noise and thought his saw was bad___(???) Well this is just my opinion of my experience, my saws have years on them and still run like the day I got them. To each his/her own, did not mean to upset anyone just wanted to post my experience.


PS. if anyone is interested in proper muffler mods there is a bunch of info out there. Just make sure it is the correct info for your type of engine.

 

[20 20]

unless you have clipped a few trees with your street bike you are on the wrong thread

From experience when I was much younger, I can say this hurts like heck :laughing: To top it off they were thorn trees

 

[Coyote machine]

Where's the OP and his answers to questions like: what are you going to use whatever saw you buy for?
How much experience do you have running saws of any size, etc.?
You guys can go on about mods, and 2 and 4 cycle engines and exhaust velocity/ backpressure for the rest of time- makes NO difference in this thread. And as far as how long saws last; more pertinent to this thread it depends on who is using the saw and for what purpose.
When I started using saws around 12 years old and began working as a ground guy for a large independent tree company run by two German brothers ALL we ever used was Stihl saws with no chain brakes, no safety chain, no mods of any kind, and ALL the Stihl saws were from western Germany. We ran big Ford 600's, ( I believe was the model designation) trucks with SCREAMINGLY loud chippers attached to pintle hooks on the rear end. No ear protection, and consequently some of the biggest headaches of my life by the end of the day. We also had two 100' telescoping cranes on Ford flatbed trucks that had outriggers. We used a hemp type of climbing rope and actual climbing spikes on almost all trees we climbed. Sometimes working solo on huge corporate office lots elevating huge trees by the end of the day trying to chip up the branches I nearly got caught in the chipper's feeder more than once.
We went through saws like no tomorrow. They got dropped from trees from 80' up, dropped from the crane truck, or onto it, run over by accident, you name it we did it. We broke off handles, bent bars, wrecked chains, all a part of trying to make a living. Most of the guys I worked with were Vietnam Vets, and they were CRAZY with the saws. I had one guy who was not real experienced pull a saw from a cut and come back on me and cut my jeans just below my knee; (when another guy and I were helping to push a tree he had misjudged the lean on). Needless to say that was one of the closest calls I've ever had to being seriously hurt on the job by someone else. Live and learn if one is so fortunate in the tree business.
My current tree pro who does what I'm no longer willing or able to do goes through Stihl Pro saws at least one per year. He is a MANIAC with a saw and I maintain at least 20' from him at all times.
He usually runs them over or they might fall from a tree or off the truck/tractor, etc. depending on what he's doing. Sometimes they're worth repairing when they cost more than $1000/saw. Other times he just scrap heaps them. It's very hard to make a good living today as a pro tree guy whether as a one man band or as a big outfit. Speed is of the essence and speed can cause an increase in negative outcomes for the guys wielding the saws.
Stihl is it as far as I'm concerned. Pro saws, homeowner saws, all kinds of saws. Having a reliable dealer or two in an area is important as well.