Stihl MS260

[wildwes]

So does the WT-426... NO limiter caps here!


Sorry, but it is not BS or a rumor. It is firmly based in the design of the carb. A 1/16 turn on a WT-194 is equivalent to a 1/4 turn on WT-426. That being said, you would definitely notice the difference side-by-side. However, if you have never experienced tuning a bypass carb before you may not notice the difference.

I don't mean this in any way to be a smart alec, just an honest question- would you explain the difference? I have never found the 194 to be hard to adjust or finicky, but I also generally adjust with a very fine/light touch until I get it just right, and have no problem getting it right. I also don't mind spending some time cutting with one and tweaking it until it is right.

 

[bwalker]

So does the WT-426... NO limiter caps here!


Sorry, but it is not BS or a rumor. It is firmly based in the design of the carb. A 1/16 turn on a WT-194 is equivalent to a 1/4 turn on WT-426. That being said, you would definitely notice the difference side-by-side. However, if you have never experienced tuning a bypass carb before you may not notice the difference.

I've tuned a 194... it's not hard regardless of the design.

 

[Mad Professor]

So does the WT-426... NO limiter caps here!


Sorry, but it is not BS or a rumor. It is firmly based in the design of the carb. A 1/16 turn on a WT-194 is equivalent to a 1/4 turn on WT-426. That being said, you would definitely notice the difference side-by-side. However, if you have never experienced tuning a bypass carb before you may not notice the difference.

This has good explanation of the Walboro carbs

 

[SteveSr]

I don't mean this in any way to be a smart alec, just an honest question- would you explain the difference? I have never found the 194 to be hard to adjust or finicky, but I also generally adjust with a very fine/light touch until I get it just right, and have no problem getting it right. I also don't mind spending some time cutting with one and tweaking it until it is right.

The WT-194 is a "traditional" design where the entire fuel flow goes through the needle screws.

The WT-426 is a first generation EPA design which makes the needle adjustments less sensitive i.e. harder to mis-adjust. They also added o-ring seals on the needles to prevent any air from getting in via the needle screw threads and upsetting the mixture.

The WT-426 is a "bypass" carb design. With these carburetors the majority of the fuel flow bypasses the needles and instead goes through fixed jets in the metering chamber. The remaining fuel flow then goes through the adjustment needles. The percentage of the fuel going through each path varies with the individual carb design. With the WT-426 it is probably divided 75% fixed and 25% adjustable.

Just about all of the newer carbs are of this bypass design and the adjustable part of the flow has decreased steadily as manufacturers seek to meet tighter EPA limits. I recently rebuilt a Stihl MS251 and 3/4 of a turn with the "H" screw made very little difference in the running behavior of the engine.

 

[wildwes]

The WT-194 is a "traditional" design where the entire fuel flow goes through the needle screws.

The WT-426 is a first generation EPA design which makes the needle adjustments less sensitive i.e. harder to mis-adjust. They also added o-ring seals on the needles to prevent any air from getting in via the needle screw threads and upsetting the mixture.

The WT-426 is a "bypass" carb design. With these carburetors the majority of the fuel flow bypasses the needles and instead goes through fixed jets in the metering chamber. The remaining fuel flow then goes through the adjustment needles. The percentage of the fuel going through each path varies with the individual carb design. With the WT-426 it is probably divided 75% fixed and 25% adjustable.

Just about all of the newer carbs are of this bypass design and the adjustable part of the flow has decreased steadily as manufacturers seek to meet tighter EPA limits. I recently rebuilt a Stihl MS251 and 3/4 of a turn with the "H" screw made very little difference in the running behavior of the engine.

Thank you for the clarification. I admit I have very little experience wrenching on any of the newer saws- the few that I own are pretty much stock..
When I adjust something I usually make very fine adjustments, so I guess the WT194 has never given me any trouble for that reason. I just put a WT-194 on a MS260 and muffler modded it today. Swapped the metering cover out off of the OEM carb. It's like having a completely different saw. Before it struggled when burying a 16" .325 bar with a full chisel chain in oak. Now it pulls 16" 3/8 full chisel very well. They may be older designs, but I sure like the WT194 on a MS260

 

[bwalker]

Thank you for the clarification. I admit I have very little experience wrenching on any of the newer saws- the few that I own are pretty much stock..
When I adjust something I usually make very fine adjustments, so I guess the WT194 has never given me any trouble for that reason. I just put a WT-194 on a MS260 and muffler modded it today. Swapped the metering cover out off of the OEM carb. It's like having a completely different saw. Before it struggled when burying a 16" .325 bar with a full chisel chain in oak. Now it pulls 16" 3/8 full chisel very well. They may be older designs, but I sure like the WT194 on a MS260

I'm sorry, but a carb with a limited adjustment ra ge just doesn't sound great to me. On top of that the WT-194 has a bigger bore, which is a bottle neck on the 260.
My memory is a bit foggy, but I seam to remember guys that ran the 426 having to change jets out to get them to work?
Regardless, I will take the 194..."difficult" adjustments and all.

 

[bwalker]

Thank you for the clarification. I admit I have very little experience wrenching on any of the newer saws- the few that I own are pretty much stock..
When I adjust something I usually make very fine adjustments, so I guess the WT194 has never given me any trouble for that reason. I just put a WT-194 on a MS260 and muffler modded it today. Swapped the metering cover out off of the OEM carb. It's like having a completely different saw. Before it struggled when burying a 16" .325 bar with a full chisel chain in oak. Now it pulls 16" 3/8 full chisel very well. They may be older designs, but I sure like the WT194 on a MS260

Delete the base gasket, advance the timing a hair and trim the choke next.

 

[Captain Bruce]

The WT-194 is an old school fully adjustable carb which can be a bit "touchy" to tune. You will also need to replace the metering cover with a compensating variety for the 260.

You can also use a WT-426. It has the correct metering cover so it is a drop-in replacement. The WT-426 is also fully adjustable but the screws aren't quite as touchy because only a portion of the fuel goes through the needles. I think that this carb was uses on the later 026 Pro and earlier 260 Pro saws.

WT-426, period. Its served me well on these 50cc lightweights for 20 years....

 

[wildwes]

WT-426, period. Its served me well on these 50cc lightweights for 20 years....

Unless you can find good WT-194 carbs for $10-$15
That is one reason why I keep on using them, instead of the 426, and they have served me well ever since I bought my first chainsaw, which was a very used 026 with a 194.

 

[dmb2613]

A 194 needs to be adjusted more for temperature change than a 426. I think a 426 is better for the average chainsaw user. How ever I like the 194 better lol

 

[pioneerguy600]

I use 194`s on all my 026`s and MS260`s, carry a tuning screwdriver at all times and make adjustments several times a day, all saws are ported so not an average user.