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SU Carb question

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lesingepsycho

Jedi Warrior
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Hey gang, /ubbthreads/images/graemlins/savewave.gif
I finished the rebuild on the SU's. Big thanks to everybody who helped and gave advice! Cheers! /ubbthreads/images/graemlins/cheers.gif It took me about an hour to get the Weber out and get the car ready to take the SU's. It took about another hour to get the SU's hooked up. Got the car started and it was running really roughly and when I opened the throttle it would die after a couple seconds. OK, fuel problem. Cracked open the front float bowl and it looked great, fuel was at proper level, all was well. Put the front back together and pulled the lid on the rear and it was bone dry. It hadn't ever seen a single drop of gas so with the top still open on the rear, I turned the ignition back on... nothing. So I unhooked the line to the rear carb at the front carb... nothing. It should have been spewing petrol all over my radiator. It seems like the gas is filling the front float bowl fine but none is being diverted towards the rear. What could be causing this? I mean, there isn't even anything to disassemble or service on the float bowl lid is there? Do I have to try different lids until I find one that works? I have about three others that I could swap out but I already spent a fair amount of time spit-shinning this one. Thanks again everybody!! /ubbthreads/images/graemlins/cool.gif

JACK
 
check the passages between the front carb needle valve and where the hose takes off to the rear carb. Somthing must be in there blocking it. If it's a banjo fitting make sure there isn't a gasket where it shouldn't be, blocking the flow. it's gotta be right in there. good luck
 
Are you hooking up the rear carb from the overflow nipple on the front lid?
The front lid has 2 mipples, they are straight thru.
Later carbs would have 3 nipples on the front lid, one is an overflow.
 
The one i was using only had 2 nipples and I was pretty sure they were straight thru. There must be something blocking it but I thought I did a good job of cleaning everything and of course it got new needle valves with the rebuild and like I said, the float seemed to be adjusted properly and the needle valve seemed to be doing it's job. I'll have to check and see if there's blockage. Can I poke around in there with a piece of wire or will i damage something?

JACK
 
Thats fine, as long as you're not poking the needle valve. But that's not really that close to where you're poking. Yes you should be able to see straight through the two nipples if they are inline.
A good piece of coathanger should do the trick.
 
OK gang, I figured out what the problem was. It seems somehow, (I imagine at the hands of my Dad or a PO or possibly even myself back in my less knowledgeable High School days) the float bowl lid on the front carb got mixed up with a REAR float bowl lid from a later model set of SUs, which indeed has two nipples, but one of which is intended not to pass fuel through to a second carb but rather to allow ventilation of fumes for 'recycling' if you will. The two diffent lids look very similar each having two nipples coming off at 90 degrees seperation. I finally figured it out when I took the lid off and blew through each of the nipples while holding the float in both the open and closed position. Then it was pretty obvious what was going on. Anyways, problem solved, and thanks again to everyone who helped out. With the help of the other thread on tuning SU's, I think I even managed to get them running rather well. Cheers all /ubbthreads/images/graemlins/cheers.gif

JACK
 
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