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ok i have a stock hitachi carb and i can go as fast as i wont to in my truck. but for some reason my secondary wont open. i checked the vacuum hoses and i didn't see anything wrong with them. does it work of vacuum or something else? i cant imagine but type of power i could have if it would open. anybody with knowledge thanks.

billy

I can't give you the exact figures, but when the primary throttle plate approaches 90 degrees or full open the linkage unlocks the secondary throttle plate and allows manifold vacuum to move the diaphram linkage to open the secondary.

i can open it manuelly, so it does run of vacuum?

Yup, vacuum operated. Facing forward, same direction as the truck, on the top back left corner of the carb is a short maybe 1 and 1/2 inch diameter metal cylinder with with a short curlicue 1/4 inch vacuum hose connected to it. The diaphragm is inside this with the other side having the linkage that connects to the secondary throttle. I suspect the diaphragm has a hole in it and leaking. Pull off the short hose and connect a longer hose onto the diaphragm housing. Suck on it and see if you can draw air. If so, I'm correct. If you can't get air, then you're not getting a vacuum or the linkage is not moving. Sorry I can't post a photo, but I run a Weber. If you can afford one, anyone here would recommend changing over.

Ain't these computers great. We're about 1500 miles apart, but we can troubleshoot your LUV problem. I troubleshot a computer simulator problem about a month ago with a guy in Australia. I don't know how far away that is exactly. Thousands of miles, though.

i worked on it all day and i suspect that it is a hole in the diaphram. i changed all my vacuum hoses and it still wont open unless i open it manually. does anyone have a spare carb that has a good diaphram on it. i cant afford a weber right now but if i could i would definitely get one. thanks robert for the advice i guess i need to replace the whole secondary diaphram?

Run a longer piece of vac hose off of it and lightly suck on the hose, put your tounge over the end of the hose and see if the diaphram stays or releases. If it releases, it's bad.

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OK, I'm over it. Where's the beer?

which hose is it do i need to check, cause i changed all of them and im lost.

To check a diaphram, hook a long hose to the diaphram you want to check.

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OK, I'm over it. Where's the beer?