Stihl MS260 / Walbro WTE-1 Weirdness?

[SteveSr]

Saw is a late 2006 vintage. Engine was completely bone stock. It had signs of running rich as well as the fuel pooling in the intake as is known for this model.

I mostly solved the fuel pooling with an "L" adjustment. This worked pretty well but later I noticed that the "L" screw as only 3/4 instead of the factory 1 turn out. Thinking that the diaphragms had gotten stiff I decide to install an OEM carb kit. At the same time I decided to perform the common 1-hole to 3-hole muffler mod.

I put everything back together and when I ran the saw it was definitely leaner throughout the range. I think I had to open both the "L" and "H" about a half turn more from their previous settings. It seems to run well there but the idle is now borderline too high with the throttle plate closed. Enriching the "L" will lower the idle speed but also increase fuel pooling.

I have muffler modded these saws before without incident but they had different model carburetors. Is this something that is likely specific to this particular carb model? Other thoughts?


Thanks,
Steve

 

[Mad Professor]

Piston in good shape/not worn? Worn skirt will piss mix back into carb.

 

[SteveSr]

Piston in good shape/not worn? Worn skirt will piss mix back into carb.

Piston and saw are low hours and in good shape.

What running behavior issues would this cause other than to dirty the air filter with mix?

 

[pioneerguy600]

I change every 026 ,MS260 over to a WT194 ,I don`t bother trying to figure out why they run lean, they just do. TerrySyd is the guy to ask about how a carb works internally. I usually have around 10 -15 of this model saw on hand, I want a carb that can deliver fuel to a ported,muffler modded engine.

 

[SteveSr]

I change every 026 ,MS260 over to a WT194 ,I don`t bother trying to figure out why they run lean, they just do. TerrySyd is the guy to ask about how a carb works internally. I usually have around 10 -15 of this model saw on hand, I want a carb that can deliver fuel to a ported,muffler modded engine.

Thanks for your input. Even with the MM the WTE-1 carb can be set to provide enough fuel at WOT. The issue comes in at the bottom end (fuel pooling) and at idle.

I am going to try a WT-426 and see if that helps the situation any. It was one of the official carbs used on this series.

 

[pioneerguy600]

The WT -426 is a different feed carb than the 194. The 194 is a fully adjustable carb on its screws where the 426 is a bypass fed carb, fuel on the H side bypasses the H screw even if is closed tight. At least the engine gets some fuel that may prevent scoring if the H side is adjusted toward lean. It is a more difficult carb to tune on the 026, one of the boggers coming off idle to transition to WOT.

 

[bwalker]

I change every 026 ,MS260 over to a WT194 ,I don`t bother trying to figure out why they run lean, they just do. TerrySyd is the guy to ask about how a carb works internally. I usually have around 10 -15 of this model saw on hand, I want a carb that can deliver fuel to a ported,muffler modded engine.

That's what I always did as well. The 260's with fixed HS jet carbs were basically not runnable at sea level stock. The WT194 has a bigger bore as well and makes slightly more power once you muffler mod it.

 

[pioneerguy600]

All my 026 and MS260`S are ported and muffler modded and all have 194`s on them as adjustment is really necessary, plus I can tune out the annoying bog or stumble from idle over to WOT.