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Hi guys. Name is Steve. First post.

I have an 81 Honda gl500 that now won't start.

I took off my old carb and installed two new performance carbs from Murray's. My petcock has (what I believe is) a vacuum hose that ran to my right carb. I don't see the same brass connector on either of the new ones. Is it needed and am I expected to do this myself?

Thanks for your help
 

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You can either fit a port or replace the vacuum operated petcock with a manual one..

The petcock you have can also be modified to work without vacuum but I'll leave that to somebody that has actually done it to explain.
 

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IIRC the spring is on the vacuum side of the diaphragm, Vacuum pulls the diaphragm against the spring pressure allowing fuel to flow. Once the engine is stopped the spring pushes the diaphragm to seal fuel flow. Remove the four screws and remove the cover. Place the spring on the other side of the diaphragm and replace the cover. Now the spring is pushing the diaphragm to the open position. Join the vacuum barb and the drain barb with a short length of appropriate tubing. Now you have to turn the petcock to the off position by hand.
 

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There’s another option: use one of the vacuum ports that are on the intake manifolds. They are meant for carb balancing but will work for this too. You just need to get a fitting that will screw into it. I have some with my balancer. So you may be able to source one. I think they’re 6mm.
 
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