Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Stihl => Topic started by: Gregsl on November 04, 2013, 08:30:11 am

Title: Did I go a little too far with my 260 exhaust mod?
Post by: Gregsl on November 04, 2013, 08:30:11 am
Hi,

I might have rushed things a bit (I try to get all my workshop stuff done when the fiancee is at yoga...)  I think I might have opened up the exhaust a little too much.  I havent been able to try the spaghetti method to check the percentage.  Also, I've heard that you shouldnt open it up more than 80% of your original exhaust port.  Does this mean 80% of the exhaust port size in the cylinder... or the exhaust port at the outside of the cylinder..

I've attached a couple pics to show what I did.  Any thoughts?

I dont mind buying a new muffler if i have to.  I'll take more time to do it next time...
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: 660magnum on November 04, 2013, 08:43:21 am
My chainsaw mufflers are slightly larger than the cylinder outlet of the exhaust.

The outlets of the mufflers are larger than stock. The cookie cutter race saws have outlets as big in area as the exhaust outlet of the cylinder.
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Gregsl on November 05, 2013, 08:42:46 am
sorry, my quote button isnt working for some reason : 

"My chainsaw mufflers are slightly larger than the cylinder outlet of the exhaust.

The outlets of the mufflers are larger than stock. The cookie cutter race saws have outlets as big in area as the exhaust outlet of the cylinder."

Do you mean the cylinder outlet that the exhaust gasket attaches to? (the one i refer to as outside cylinder in my diagram).  Reason i am asking is there is quite a bit of difference in the opening inside the cylinder versus outside at the exhaust flange side...
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: 660magnum on November 05, 2013, 10:36:47 am
Yes, The outside of the cylinder on my ported saws are significantly larger than the inside of the cylinder.

The muffler outlet is as large as the outside of the exhaust port on the cylinder. These chainsaws are much louder than a stock chainsaw.
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: H 2 H on November 05, 2013, 12:10:28 pm
026 MM

(http://i59.photobucket.com/albums/g317/H2H_PHOTOS/MS%20250/026/001a_zps8e03dea2.jpg)
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Gregsl on November 05, 2013, 03:45:27 pm
wow, how loud is that saw?
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: HolmenTree on November 05, 2013, 04:49:53 pm
Greg, every saw is different , my 066 Mag Stihl with it's dual outlet muffler comes with a full baffle inside the muffler over the exhaust port . It puts out all the power I need for what the saw is running at stock.
When I played with tuned exhaust pipes on my race saws years ago when most members here weren't born yet, I experimented with the "exhaust outlet " stinger on the pipe by cutting off lengths of the stinger until the the timed cuts in the log cant dropped in Elapsed Time, that point in length was where I got the best h.p. Same example goes for outlet diameter, the stop watch never lies. ;)
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: H 2 H on November 05, 2013, 05:23:12 pm
wow, how loud is that saw?

Just a little louder than my other my other 026

IMO feel it runs better also

You have to remember the screen cuts the sound also
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Gregsl on November 05, 2013, 05:25:08 pm
Cool, so I guess I don't have to worry about my modified opening being too big then.

I might still buy another replacement muffler and do a better job of the mod
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: HolmenTree on November 05, 2013, 05:26:53 pm
Cool, so I guess I don't have to worry about my modified opening being too big then.

I might still buy another replacement muffler and do a better job of the mod
If you have a torch to braze silver solder or a mig welder anything can be repaired :D
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: H 2 H on November 05, 2013, 05:30:46 pm
Every saw I own I have atleast one extra muffler even my MS 261 and MS 461

Make sure you have good working carbs to adjust to the new muffler also
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: HolmenTree on November 05, 2013, 07:04:06 pm
Well I don't do saw repair or mods for other folk, but I can say I have boxes of useless dirty old saw parts up in my attic that need to be recycled. :)
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Old Iron Logging on November 05, 2013, 07:51:29 pm
Timberwolf did some work with large exhaust openings. Some worked very well. My 026 was large, no pics. This 675 had the largest opening on any saws that I got from him.
https://www.youtube.com/watch?v=vh5GBZgcrMw
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Gregsl on November 05, 2013, 08:46:50 pm
Lol HolmenTree. If you have a spare 260 muffler in that dusty box of parts you should send it out east. I'm in NS.
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Al Smith on November 05, 2013, 09:24:01 pm
Once upon a time there was an arborist in Cincinati who posted on another site who's name I won't mention .

He got the bright idea to hog the muffler out on a nearly new Stihl 880 or 088 he was real proud of but neglected to increase the high speed jet .I nearly pleaded with him to make some provisions which fell upon deaf ears .Sure enough a month or two later on flea bay for sale a Stihl 088 ,cooked cylinder .
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: HolmenTree on November 05, 2013, 10:32:29 pm
Lol HolmenTree. If you have a spare 260 muffler in that dusty box of parts you should send it out east. I'm in NS.
Hello Gregs, no 026/260 parts,
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Gregsl on November 06, 2013, 08:58:00 am
LOL, no worries HolmenTree

I almost have the saw completely torn down with all parts inspected and labelled in ziplocks. I am awaiting my meteor piston kit and gasket set from Baileys so I have some time to research some of the unknowns with this rebuild.  Thanks to this site (and other sites)  the unkowns become less each day.

Next step, fabricating my homemade case splitter and flywheel puller... Then a thorough degreasing of all parts.

G

Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: HolmenTree on November 06, 2013, 11:04:15 am
I have a 5 gal parts washer that I keep outdoors by the front door of my workshop. I mounted it inside a stripped out barbeque, the lid of the barbeque keeps the parts washer and solvent protected from the elements and it's sitting waist high for easy use.
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Adirondackstihl on November 06, 2013, 07:42:15 pm
homemade case splitter and flywheel puller...

Case splitter = brass hammer

flywheel puller = $8 from STIHL
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Gregsl on November 08, 2013, 09:44:56 am
So i stole an idea from someone else and used Sketchup to calculate the area of all the openings.

Anyways.  The black rectangle represents the "ideal" opening of the exhaust and is based on the commonly accepted 80% of the exhaust outlet (outside-cylinder) and ~150% of the exhaust outlet (in-cylinder) rule of thumb

As you can see with my existing modified exhaust hole, i can almost double the size and be within the rule of thumb specs.  I think i will try it 'as is' and see how it goes and then open it up further based on those results.

There was an interesting post on another site where a guy did 5 successive exhaust mods on a 260 and analyzed the results in terms of engine/exhaust temp and sound level. He started with the muffler that had the single 1/4 inch hole and then opened it up sequentially to be a 1.5 inch x 3/8 rectangle... which is basically the same dimensions of the "ideal" rectangle in my pic.

G
Title: Re: Did I go a little too far with my 260 exhaust mod?
Post by: Moparmyway on November 09, 2013, 10:09:18 am
IIRC, that writeup showed that too larg of an opening didnt reduce power much at all, although it did consume more fuel. I believe the drop in power occurred near 125% of the cylinder opening.