Pick the best carb for MS260 Pro...

[Terry Syd]

I don't know what the air filter on the 026 is like, but on the 029-039 series it is pathetic. I made up my own filter by removing the felt from an 029 filter, drilling the cage, gluing some thin filter foam over the cage and then sewing some flannel from an old shirt over the whole thing. It increased the surface area probably 300%. It actually filters better than a stock filter, probably because there is less suction to pull stuff through.

I did a test one time of the filter. I had used the saw three times without cleaning the 'high-flow filter'. I had a tach on the saw and ran it up to WOT to get a reading, then I put on a brand new, never used, stock filter and checked the RPM again. The clean, new stock filter showed a 75 rpm drop. I didn't bother testing a dirty stock filter.

Bottom line, if the filter is the bottle neck in the intake system, then a bigger carb isn't going to improve the air flow.

 

[bwalker]

Wt-194

 

[drf256]

I don't know what the air filter on the 026 is like, but on the 029-039 series it is pathetic. I made up my own filter by removing the felt from an 029 filter, drilling the cage, gluing some thin filter foam over the cage and then sewing some flannel from an old shirt over the whole thing. It increased the surface area probably 300%. It actually filters better than a stock filter, probably because there is less suction to pull stuff through.

I did a test one time of the filter. I had used the saw three times without cleaning the 'high-flow filter'. I had a tach on the saw and ran it up to WOT to get a reading, then I put on a brand new, never used, stock filter and checked the RPM again. The clean, new stock filter showed a 75 rpm drop. I didn't bother testing a dirty stock filter.

Bottom line, if the filter is the bottle neck in the intake system, then a bigger carb isn't going to improve the air flow.

The 026's weak link is its air filter. The combo of tight flocking and a choke spring that can weaken is the death nail for serious performance upgrades. You need to get a fine screen metal filter, 1611 I believe, for theses saws to run. This is an expensive and hard to find filter. I'm in the process of trying to make my own.

The MS260 has a bigger and less restrictive filter that's available cheaply. You need a different AF cover and a different tank vent for functionality.

What the advantage of an 039 over an 044 carb?

BTW, how are you guys rotating the fuel inlet around 180* and capping the air horn on the metering plate cover.

 

[Terry Syd]

What the advantage of an 039 over an 044 carb?

Bugger if I know. The 044 carb, although a Zama carb, is actually based on the early Walbro circuit, that is, it doesn't have the separate mixture for the idle circuit. It has two air bleed/transition holes fairly close together that are regulated by the low speed needle.

The 029-039 carb has the second air bleed hole/transition hole up further in the venturi. I like the Walbro circuit better.

Because of the position of the air bleed/transition holes in the 029-039 carb, you can have more 'play' with the way the transition comes in.

Although the Zama 'twin jet' is easier to jet for an engine (see Poleman for a carb), if you work with the metering spring in the Walbro, you can dial in the low speed circuit to get a good cross-over between the two circuits.

Perhaps someone with a set of Walbro springs can recommend a metering spring for the application.

 

[drf256]

@Terry Syd

I just finished porting an MS260.

It's got an AM 044 carb on it with a modified version of a nylon Hutzle AF on it.

250psi comp. Saw was struggling to hit 13k and be fat enough.

So I popped the AF off and the saw came to life. Now it's flowing lots of air, but not enough fuel.

I have the H 3-1/2 turns out, maybe more. It's 4 stroking at 15,500 now. I'd like it a bit more fat. I'm still 4 stroking at 16k, but just a bit.

If I pop the AF back on with no change, I'm pig rich at 12000.

I plan on a V stack with a KN for racing, and a modded metal screen AF and cover for regular use.

What mods can I do to flow more fuel? Would you have a pic Terry?

 

[Terry Syd]

If the H screw is all the way out, you may have to open the L screw a bit to fatten it up. If that creates a problem with the idle and transition, then try shimming up the metering spring or find a slightly stronger spring.

My ugly filter for the 029 is just as I described. The extensively drilled cage has the thin air filter foam glued over it to hold the flannel shirt material. I needed the bit of foam to hold the shirt material away from the holes.

I also did another trick left over from my days of racing a rotary valve engine. I spent some time with a guy named Jerry Branch who ran 'Flometrics' - a porting facility with a flow bench. Jerry was a genius (look him up on the 'net). He also ran the same rotary valve engine as mine and he showed me a trick on the outer cover to get the engine to breath better. He had created a raised area on the inside of the cover that would turn and direct the flow into the carb. Worked a treat.

I made up a similar shape using GB Weld on the inside of my filter. I don't know if it works, but I feel better with it in there.

 

[Basher]

The 026's weak link is its air filter. The combo of tight flocking and a choke spring that can weaken is the death nail for serious performance upgrades. You need to get a fine screen metal filter, 1611 I believe, for theses saws to run. This is an expensive and hard to find filter. I'm in the process of trying to make my own.

The MS260 has a bigger and less restrictive filter that's available cheaply. You need a different AF cover and a different tank vent for functionality.

What the advantage of an 039 over an 044 carb?

BTW, how are you guys rotating the fuel inlet around 180* and capping the air horn on the metering plate cover.

The hole that the choke flap closes against is the real weak link/greatest restriction,in these filters, does not matter if its an 026 or MS260 filter. Do away with the choke and open the filter hole up a tad bigger than the carb venturi, toss the spitback guard, then the filter can flow plenty of air for the carb. I change all of mine over to mesh type 260 filters, they have a larger area for air to pass through but they still have that restrictive choke hole so on my own saws the choke gets tossed.

 

[Duane(Pa)]

These air filters leave a lot to be desired.....I have found a ton (I exaggerate) of fine crap INSIDE the filter after 3-4 tanks of fuel. It was easy enough to clean up, being that it was so fine. I plan to do a little recon on how it's getting in there and see if I can seal it up some.

 

[TJ the Chainsaw Mechanic]

Quadrajet might work nicely.

 

[stihl_head1982]

These air filters leave a lot to be desired.....I have found a ton (I exaggerate) of fine crap INSIDE the filter after 3-4 tanks of fuel. It was easy enough to clean up, being that it was so fine. I plan to do a little recon on how it's getting in there and see if I can seal it up some.

There does need to be another filter made to address this issue. Thus far I have not found anything to keep the "stuff" out of the inside. Perhaps there is someone who would design and market a new filter for these?

 

[Terry Syd]

As I indicated in post #41 above, the high flow filter actually filters better than the stock filter - and all I'm using for a filter is a piece of flannel. I expect that the reason the fines aren't getting sucked through is there is less suction (because of the increased area) trying to pull them through the cloth. I was surprised at how well it filtered.

Perhaps something similar can be made for the 026 to try and increase the area of filtration.

 

[drf256]

The hole that the choke flap closes against is the real weak link/greatest restriction,in these filters, does not matter if its an 026 or MS260 filter. Do away with the choke and open the filter hole up a tad bigger than the carb venturi, toss the spitback guard, then the filter can flow plenty of air for the carb. I change all of mine over to mesh type 260 filters, they have a larger area for air to pass through but they still have that restrictive choke hole so on my own saws the choke gets tossed.

As I indicated in post #41 above, the high flow filter actually filters better than the stock filter - and all I'm using for a filter is a piece of flannel. I expect that the reason the fines aren't getting sucked through is there is less suction (because of the increased area) trying to pull them through the cloth. I was surprised at how well it filtered.

Perhaps something similar can be made for the 026 to try and increase the area of filtration.

The filter that was giving me all the problem was a Hutzl MS260 filter. The spitback guard and the choke were removed already, and the opening was opened to larger than the 044 throat.

There's not a lot of real estate under an 026 back cover. Being no fine screen metal filter exists for the MS260 (they do for 026 only) I cut out most of the flocking and made my own metal filter by attaching 50 micron screen to the filter with 3M adhesive.

I also plan to add some vents in the cover itself.

Basher, your 026 runs amazingly well. I build 026's, and yours is gassed up in my garage for emergencies, and it's staying there. The one I just built is a littler spicier than the MS260 I have of yours. The stock filter membrane just can't move enough air for this saw with the 044 carb.

 

[Basher]

I agree that the stock or AM filters cannot move enough air through them for an 044 carb, for that application I would make my own filter covering for over the stock frame like Terry stated. I will spend some time making up a new revamped filter for my next ported 026.

 

[Terry Syd]

There's not a lot of real estate under an 026 back cover.

I've started running my saws with the back cover OFF. Not only does it insure cool air to the engine, but the air filters pick up less dust. Some other guys on the forum noticed the same thing about cleaner air filters. I've watched the air filters after I finish a cut and when the revs drop, so does stuff off the air filter. If the cover is on, the stuff stays close to the filter, while with it off the stuff can fall away from the saw - at least that is my theory as to why the filter stays cleaner.

Just try it and see what you think. If it is staying cleaner and you decide to run with the cover off, then make up a bigger air filter that won't fit in the cover. You can always put a stock filter and cover on if you are going to cut in the rain. I hear some people do cut in the rain, but I've never done it and don't intend to - too old for that crap.

 

[Deets066]

Does anyone have any experience with the Tilly HU 54 carb? It came on my 024 super and I was suprized that it hasn't been mentioned in this thread yet.

 

[drf256]

The hole that the choke flap closes against is the real weak link/greatest restriction,in these filters, does not matter if its an 026 or MS260 filter. Do away with the choke and open the filter hole up a tad bigger than the carb venturi, toss the spitback guard, then the filter can flow plenty of air for the carb. I change all of mine over to mesh type 260 filters, they have a larger area for air to pass through but they still have that restrictive choke hole so on my own saws the choke gets tossed.

Your 026's are a work of art. Not sure how you get that much power and still are able to run a stock piston.

Kudos to you bud.

 

[huskihl]

What boot are you guys using? I got into mine last night and didn't want to start carving plastic past the point of no return til you guinea pigs get all the trial and error figured out . The 044 carb is 10mm ish longer than a 194. Is there really any room for air with the cover on anyway?

 

[Basher]

Your 026's are a work of art. Not sure how you get that much power and still are able to run a stock piston.

Kudos to you bud.

Thanks,
It comes from just little things in several places. I have been porting for more than 40 years now. I have been building 026`s for about 10 years and did things in small steps, some work, some don`t but eventually you find a combination that works. I build stronger saws but have not released them, just use them myself.

 

[drf256]

What boot are you guys using? I got into mine last night and didn't want to start carving plastic past the point of no return til you guinea pigs get all the trial and error figured out . The 044 carb is 10mm ish longer than a 194. Is there really any room for air with the cover on anyway?

The saw I'm working on was using an 038 boot. I found the boot to be too long and to have a square bottom at the port entry point which would interfere with flow. That flat portion would site again the flat wall of an 038 port. The stud rotation of the 026 made it just not fit right.

An 044 boot with some sealant at the jug lip seems to work just fine.

The carb and air filter do still fit.

I can see narrowing the carb body on a lathe for sure. Not sure how close I could get though.

 

[czar800]

I also plan to add some vents in the cover itself.

What exactly are you planning on doing?

I've been doing this...??? Are you doing something different?