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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?

Please post the numbers stamped on the original carb.

Rivets said:

Please post the numbers stamped on the original carb.

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C1U-K42 or C1U-K78. I have seen either of these on this style blower ... the older gray Echo's.

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

StarTech said:

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

Click to expand...

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.