MS260 carb & muffler mod questions.

[rustyb]

Having read all the benefits here about the muffler mods, it seems like a no brainer so I have decided to do it. But, even after reading all the posts, I'm still not clear on the carb issues. A couple folks here have mentioned doing the muffler mods then taking the saw into the dealer to have tuned. I like this idea BUT, I get the strong impression my local dealer is a stickler and I don't think he'd be too keen to hear that I modified the muffler. On top of that, I'm not even sure if this dealer is a good tuner. Of course I could ask but I suspect he isn't going to tell me if he isn't or he may just say the saw doesn't even need tuned……I really don't know.

So, with that said, I may have to work on the saw myself. As mentioned in an earlier post of mine, I thought this saw was not revving as freely or cutting as well as it could. I know it'll run better with some more time but I would also assume the saw to be running too rich. If it was too rich and opening up the muffler tends to lean the saw, is it possible that if I did the muffler mods, the fuel air/mixture might be corrected or is that wishful thinking?

I used to race motocross in the 80's and though I wasn't a super star mechanic, I did do all my tuning. However, I had no fancy tachs or other such gadgets and went by engine sound and the color of the plug after running the bike wide open for a bit. If the plug was dark & oily, it was running too rich. If it was white, too lean and if tan, just right. Does tuning a saw work in the same way?

Perhaps all that is a moot point as I'm not even sure my carb offers enough adjustability for me to easily tune it. My saw has the typical LA screw but instead of having two places for the Low speed & High-speed adjustments above, I have three! There are three indentations and only one is open with an adjustment screw - the middle one. The left is labeled "H" and the right "L". The owners manual is of no help as it only shows two indentations…..or in other words, places for the "H" & "L". Does anyone know if this carb is the fixed jet model or another that I may be able to easily tune myself?

All advice, help and or ideas would be appreciated.

Thanks,
rusty

 

[Jacob J.]

<p>Rusty-<p/>
<p>Some dealers will void your warranty if you modify the muffler or any other part of the saw in any way. We had a guy buy a new MS-360 at my logging company's Stihl shop, and he proceeded to drill several holes in the muffler. The saw lost too much backpressure and the poor guy actually had less power. When he brought it in for a new muffler he expected us to pay for it.<p/>
<p>The carb on the newer saws doesn't leave much room for tuning, other than the adjustment screws with the limiting caps. Someone else here may be able to answer whether or not you can replace the jet in that carb, I have no idea. I have several older fully adjustable 026 carbs that have a replaceable jet. Sounds like you have a fixed jet carb though.<p/>
<p>You may want to decide if you want to void the warranty and if so, then replace the carb with an adjustable version and open the muffler up. Or better yet, send your saw to one of the mant saw tuners here and let them make it into a beast.<p/>

 

[rustyb]

Thanks for the reply Jacob.

Any one else have any ideas about my carb? I expected a whole slew of ideas on this one.

rusty

 

[stihltech]

jet

That is a fixed jet carb.
Do the muffler mod and make some cuts to see if you still have some blubber out of the cut. If not, it is time to check the inlet lever height and possibly get a new jet or hack( I mean drill) the old one. Either way will work. Get me the number off the present jet and I can show you which jet or drill you will need.

 

[jokers]

Stihltech, when you hack, err ah, ream those jets, how do you hold them? They are so tiny that it`s tough to hold them in your hand and I don`t dare put them in a vise. There must also be some sort of device to hold those tiny bits but I am unaware of what you would call it. It seems simpler although costlier and more time consuming to order new jets and find the right one by trial and error or find a used adjustable carb from a parts saw.

Russ

 

[jokers]

Just took a minute to reread this thread and realized that Stihltech also mentioned the inlet lever height which is an excellent point. Since tackling my own I have had the pleasure of working on a few others and have found the inlet lever height to be more sensitive(yeah, no kidding) with the fixed jet. Your dealer ought to be helping you out on this Rusty, that is what you get from a Stihl servicing dealer right?

Russ

 

[Jacob J.]

Hey Jokers- what I did for holding those little jets was make a jig out of two chunks of polymer decking material, I used my die grinder to grind a little indentation in each side and then clamp together in the vise with the jet inbetween, they're soft enough not to mar the jet up or crush it. Wood would work well too.

 

[rustyb]

Jokers,

Yes, I believe the dealer should help but as stated in my original post, I get the strong impression he wouldn't be keen on the muffler modifications. I could ask but if he said not to and I did any way, that might be a bit awkward if I needed his help later. I'm half way thinking about just opening up the muffler with one additional hole than telling him it seems to need a tuning....of course not telling him about my mods and hoping he won't know.

You also mentioned finding "a used adjustable carb from a parts saw". Wouldn't it be better to buy a new adj carb or are there not enough things inside a saw carb to wear out?


Stihltech,

Sorry but I'm not sure I understand your statement when you say "see if you still have some blubber out of the cut". Could you explain that? Also, this may be a dumb question but what is the "inlet lever height"? And lastly, could I use the color of the plug as a tuning indicator like I did in my moto-x days ie white=too lean, oily=too rich, tan=just right?


I really appreciate the help guys.

rusty

 

[jokers]

Hi Rusty, of course it`s your call whether or not you ask your dealer up front, but I`ll gaurantee that he notices the muffler mod as soon as he hears it. It is especially pronounced on the 026 in my opinion, maybe because the muffler is so restrictive initially.

As long as the used carb is fully intact and the needles and seats haven`t been damaged there isn`t much that a good cleaning and rebuild kit won`t fix. A new wt426 from Stihl is $64 and you can`t buy the 426 anywhere else, Stihl has exclusive rights to it.
Jacob J. actually hooked me up with the first used one I got at a killer price and since that time I`ve found a bunch of others at similar prices, but alas, they have all since departed. I CAN hook you up with a non-adjustable jet carb for your saw in several different jet sizes, LOL.

Blubber out of the cut is the sound the engine makes when it is just rich enough for top horsepower and engine longevity. It won`t rev right out and scream, but will instead four cycle a little but when it`s in a cut under a full load it will clean right up. Madsen`s site has a wav file to listen to if you don`t know what I mean. Another pretty good way to set the hi speed is to slowly and giving the saw enough time to respond, turn the Hi screw in until you hit max rpms with the throttle pegged, the saw will lean out and die off just after this point. Make note of the position of your screwdriver. Now turn the screw out until rpms drop off and the engine falters and make note of this position. Now set the screw to the midpoint between the two derived positions. I`ve always had confidence in reading the plugs the way you do. I`ve had a few people tell me I`m wrong though, but I`ve never had the negative consequences or poor performance to prove their point.

Russ

 

[herminthegoose]

fixed jet life

Just purchased my very first new stihl- carb adjustment on the huskys is too easy. Very rewarding when you finally get it right.

 

[stihltech]

jets

I have always held the jet in my fingers at used a needle nose vise grip on the bit. Sounds bad I know, but the bit is very small, and this way I do not over torque and twist the bit off. You should not be taking that much out, I think sometimes it is just a matter of cleaning the orifice.
Jokers explained the blubber pretty well. As for the plug, read it. The best running saws do seem to have a tan color on the lug, the screamers are white.

 

[rustyb]

Thanks again for the pointers and insight guys. I'll listen to the file on Madsens site. Another question though. If I'm reading correctly, there is a small chance after opening the muffler I won't even have to mess with the jets but maybe adjust the "inlet lever height". Can some one explain what the "inlet lever height" is and does?

 

[stihltech]

inlet lever

Remove the tin cover on the metering chamber side of the carburetor. Remove the diaphragm and gasket. You will then see the inlet lever. Depending on the carburetor, the lever should be flush with the top of the carburetor, or, if the lever sits in a pocket, flush with the chamber floor. This will set the mix correctly from within.
Raising the lever doesn't work because the diaphragm will push on it causing the needle to not seat and leak.

 

[jokers]

Stihltech, thanks for the heads up on how you work on these jets. I have also used torch tip cleaners and they seemed to work ok although I`m sure the orifice isn`t round when you get done. Didn`t seem to matter to performance but it is a little more work to open the hole.

Russ

 

[vsteel]

To hold the bit if you are fancy you can use a pin vise. Your local hobby shop should have them, they are used for holding tiny bits for modelers. Carb guys use them also for drilling tiny holes in things like the air bleeds on carbs (they are tiny and very sensitive) Its basically a tiny drill chuck that you use by hand.

 

[stihltech]

vise

I am sure the pin vise is the way to go, but all of us hackers have vise grips in sooooo many sizes. I at least use the small needle nose variety