260 pro muffler and carb work

hokiemike · Dec 29, 2007

After reading a lot of great info the last few weeks after I found this site, I think I've decided it's time to make some changes. I have a 260 pro to cut firewood with. Unfortunately, I got one of the ones with the fixed high jet carb. I plan on opening up the muffler, replacing the carb, and buying a tach to tune by (I don't trust myself or any one I know to do it by ear). My questions are:
1. Is there a difference between adding 2-5/16 holes vs making one large hole of equal area in the muffler?
2. If I put in a WT-194-1 carb, are there any other mods I need to do besides opening up the jet access ports in the housing? Lakeside said on a similar thread "You can fit a WT194 - swap comp end cover over". What/where is this?
3. If anyone has an IPL and service manual, I'd like to get one.
It seems many have had success opening up the muffler on this saw without replacing the carb. Are there any who haven't? I don't want to buy a $40 carb and $80 tach (DTI TT-20K) if I don't have to. Thanks for the help and a happy new year to all.

Scandy14 · Dec 29, 2007

When you change over to the Walbro 194, you will need to take the compensator (top cover of carp) off the old carb and install on the new one. That is what Lake was referring to.

A tach is a very useful tool to have when tuning saws to their optimum performance. A good investment.

blsnelling · Dec 30, 2007

PM me your email and I'll get you the IPL and service manual.

Bowtie · Dec 30, 2007

blsnelling said:
PM me your email and I'll get you the IPL and service manual.

Tried to rep you for all your posts but ya know. Thanks for all your pics of your work, and I loved the pics you posted of the GTG. I modeled my 026 port work after your 046. I finished it today, and it SCREAMS! Happy Holidays, and thanks again!

Lakeside53 · Dec 30, 2007

It's a lot easier to drill two holes than open up one large one. No difference in perfornace either way.

If you're worried about the fixed jet carb, check wot before you do anything. It's likely less then 13K. If so make two 1/4 inch holes, then test for wot. If it's less then 14k, enlarge a little, like 5/16, 3/8 etc..

blsnelling · Dec 30, 2007

Check your email.

Erick · Dec 30, 2007

Top cover on 194 carb

Top cover on your carb

Remove these 4 screws and change the top plate

Muffler mod on my MS260

hokiemike · Dec 30, 2007

Thanks for all the info guys. You'll are great! I'm probably splitting hairs about the muffler opening geometry, just trying to pick what's best and not fry my saw. When I mentioned the idea with my dealer, his concern was with decreasing the back pressure. I thought about getting just the tach and slowly increasing the opening until I got to the 14K range, but that seems like a PITA. Plus, I don't know if my carb is as intelligent as Stihl thinks!

Lakeside53 · Dec 30, 2007

The "intelligent" carb only slighty lean the mixture as your air filter blocks.

oneoldbanjo · Dec 31, 2007

I am in the same project - I bought a used MS260 without the adjustable High Speed jet and it seems to run pretty rich. Also the L jet adjustment is a little weird - it will adjust pretty well and the saw will be idling fine - then as you move the saw to cut it will suddenly drop RPM very quickly (but not stall) and then the rpm's will come back up to the normal idle.

I bought a used WT 194-1 and it is in the mail and will put in a diaphagm kit before I install it and check all hoses for hole and brittleness.

Can the carb grommet with the single hole be drilled to provide access to the H adjustment - or do I need to buy a new grommet for an 026?

Frank Boyer · Dec 31, 2007

Erick
What did you do to the muffler cover to mod it? I have a 024 and a 260 that are canidates. Nice pictures.
THANKS

Bowtie · Dec 31, 2007

Frank Boyer said:
Erick
What did you do to the muffler cover to mod it? I have a 024 and a 260 that are canidates. Nice pictures.
THANKS

Post #7 look at the square hole in the front of the muffler cover. Take off your stock cover and look at it for reference. Do some searching on here for other pics and tips, dont open it up too far, and make sure you have an adjustable high jet on the carb.

Erick · Dec 31, 2007

Frank Boyer said:
Erick
What did you do to the muffler cover to mod it? I have a 024 and a 260 that are canidates. Nice pictures.
THANKS

Frank, The big square hole in the middle was about the size of a pencil from the factory. I used a dremmel tool with a carbide bit (about $6.00 at your local harware store) to open up the hole to the square hole you see in the picture. The hole is about 85 - 90 percent of the exhaust opening at the cylinder. I pulled the screen on mine and it is easily put back on without disassembly if I'm cutting on state land. Made a pretty big difference in the way the saw runs

and I love the crack it has now.

I think I'm getting ready to molest that 026 I said I was gonna leave alone. If I do I'll get some pic's of the process so you guys can see them.

Lakeside53 · Dec 31, 2007

oneoldbanjo said:
Can the carb grommet with the single hole be drilled to provide access to the H adjustment - or do I need to buy a new grommet for an 026?

buy the new grommet

Erick · Dec 31, 2007

I have drilled them with excellent results but you need to use a larger bit than you think because the rubber will expand around the bit and close back up when you take it out...... come to think of it I think I finished the hole in that one with the same carbide bit. Can't remember now but I have done it and it worked, but like Andy said cheap enough to get a new one if your dealer has it.

Lakeside53 · Dec 31, 2007

might drill best at say -30F - a nice cold morning in Indiana - you should get one soon enough

oneoldbanjo · Dec 31, 2007

I will get a new grommet if they have one - I have tried to drill rubber before and it was less than succesful. The drill gets really hot and like you say - a big drill makes a very small hole.

Erick · Dec 31, 2007

Lakeside53 said:
might drill best at say -30F - a nice cold morning in Indiana - you should get one soon enough

Was 25* last night........ but 42* already today.

We'll get winter around March I guess. :laugh:

I'd be happy to not need waders to get the mail right now.

Frank Boyer · Dec 31, 2007

oneoldbanjo said:
I will get a new grommet if they have one - I have tried to drill rubber before and it was less than successful. The drill gets really hot and like you say - a big drill makes a very small hole.

Hole punches work well on leather and rubber. They cut the material instead of trying to do a precise ream out on an moving expansive material.

oneoldbanjo · Jan 2, 2008

The WT-194 that I ordered to replace the original carb in my MS260 (no H screw in the orginal) came in the mail on Monday morning and I stopped by the Stihl dealer in the afternoon to get a rebuild kit and the new grommet. The Stihl dealer had the rebuild kit - but did not have the grommet and where a little confused about why I needed a new one. I had not taken my saw apart yet to show them the difference in the 026 - 260 grommets and I was not real succesful at convincing them that the short black one was not the one I needed - so I decided to just try and use the orignal as I wanted to work on the saw on New Years Day.

I changed the cover on the carb to get the compensating tube for the air cleaner and installed the new diaphragms and cleaned the carb while it was apart. Drilling the white 260 grommet wasn't very hard, I started with a small sharp drill and kept increasing the size until it fit over the carb (They are all very sharp drills and worked well in the rubber/plastic). While I had the saw apart I installed a different muffler cover that had 4 holes in it as opposed to the standard single hole. I did not yet want to modify the muffler until I see how much better the saw runs with just the carb conversion. I believe the 4 hole muffler is stock for some year of 026.

The saw started and adjusted very easily and seems to run very well - but I did not yet have a chance to cut with it and will try it out this weekend.

260 pro muffler and carb work

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