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Thread: 3 screw su float bowl lid ear lengths

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    Default 3 screw su float bowl lid ear lengths

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ID:	62388superglued ears back on to measure, both lids are identicle
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ID:	62387valves are different lengths, pretty sure that means i need different length float bow lid ears
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ID:	62389the good lid, 11mm from lip to hole
    I received my su carbs in a box, mostly disassembled. I have been cleaning and reassembling them. The box of parts contained two float bowl lids, both stamped with "F" next to the Hitachi logo. The ears on both are the same length, one of the lids had the ears broken off. I have arranged to purchase another lid from someone but they said "I have several lids and all the ears are about the same length, but the mounting holes for the float are at different heights. Can you measure the height of the holes on the one you need so I can be sure to send the right one?"
    I know the lid I have, besides being broken, was probably the wrong one. The only good one I have measures about 11mm from the lid's lip to the center of the hole in the ears. Is there someone with the correct lids that would be willing to take a measurement of their ears for me?
    Last edited by putmattaway; 04-07-2013 at 01:31 PM. Reason: added pics

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    Registered User Stanley's Avatar
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    On the 3-screws the front carb has "long ears" that are 2 mm longer than the rear. The measurement to the holes is the one that matters. The long valve goes in the front. If you measure the tilt of the engine and the distance from the center of the bowls to the center of the nozzles, and do the trig, you see that 2mm is the difference in fuel level between the front and rear carbs (lower in the front one) needed to have the same relative fuel level in the front and rear nozzles.

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    Boat Anchor Repairman Captain Obvious's Avatar
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    Quote Originally Posted by Stanley View Post
    On the 3-screws the front carb has "long ears" that are 2 mm longer than the rear. The measurement to the holes is the one that matters. The long valve goes in the front. If you measure the tilt of the engine and the distance from the center of the bowls to the center of the nozzles, and do the trig, you see that 2mm is the difference in fuel level between the front and rear carbs (lower in the front one) needed to have the same relative fuel level in the front and rear nozzles.
    It's not just the tilt. It's the tilt combined with the fact that the front carb has the bowl on the uphill side of the nozzle while the rear carb has the bowl on the downhill side. If both bowls were on the same side (either side), then the tilt wouldn't mean squat.

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    Registered User Stanley's Avatar
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    Quote Originally Posted by Captain Obvious View Post
    It's not just the tilt. It's the tilt combined with the fact that the front carb has the bowl on the uphill side of the nozzle while the rear carb has the bowl on the downhill side. If both bowls were on the same side (either side), then the tilt wouldn't mean squat.
    Exactly. Seems "obvious" but that's key to understand it. For the same reason, as a post here stated a while back, the car needs to be level to set the float bowls (or the slope compensated for). If the car has a raked stance, or the driveway isn't level, it will change the setup.

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    2mm shorter ears in rear, this is what I was looking for, thanks! I found tons of info on fuel levels but nothing on ear length, other than one short one long. I suppose I should have figured it out based on the valve lengths being 2mm different. Thanks everyone for your input.

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