Echo carb changes?

JBtoro

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Have an older blower, PB2100. May need a new carb. Searching online I see 3 choices. It appears that Zama OEM has a Hi & Lo adjustment screw but two aftermarket units may not have the Lo screw. The one on the right has a slot for a screwdriver but the middle one does not. That middle, large-headed screw, on certain Echo/Zama's, has always puzzled me; From other manufacturers, I'm used to seeing a Lo & a Hi etched on the body with "L" & "H". Not looking for advice of whether or not to buy OEM vs. A/M (OEM is really $$$ & this is an old, but decent blower). Anyone own either of the A/M's & can shed some light on whether or not one can adjust the LO side?

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Rivets

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Please post the numbers stamped on the original carb.
 

JBtoro

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Please post the numbers stamped on the original carb.
C1U-K42 or C1U-K78. I have seen either of these on this style blower ... the older gray Echo's.

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StarTech

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Actually there is a C1U-K42A and K42B. Both were fully adjustable as where the C1U-K78 only has a main mixture adjustment.

So images you posted are the K42B and the K78. The K42A had a slight different setup at the mixture screws.
here is an snap shot of the K42A ipl
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JBtoro

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Actually there is a C1U-K42A and K42B. Both were fully adjustable as where the C1U-K78 only has a main mixture adjustment.

So images you posted are the K42B and the K78. The K42A had a slight different setup at the mixture screws.
here is an snap shot of the K42A ipl
View attachment 57516
Thanks.The diagram you sent does not have the middle large barrel-headed screw or whatever it is (red dots). I'm trying to see if any one knows why that piece is there and, moreover, if it is actually a LO adjustment on the rightmost carb (K78 aftermarket) because that middle piece has a slot for a flathead screwdriver (circled). Also the two aftermarket carbs have a hole where the LO speed screw would normally go (hard to see) but it is blocked.

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