Topic: 1974 cb750 carbs leaking after 10 months on a shelf

[nobody]

I did a search and wasn't able to find much information on my specific situation, most carb leaks seem to be coming from gaskets, jets, needles, or float bowls. My leak seems to be coming from the two fuel inlets between the 1-2 and 3-4 carbs, are there O rings here that can go bad? Nothing is coming out of the overflow tubes or the bowl gaskets, those are dry. I even opened the two outside float bowls and made sure they were operating properly, they shut off when the float valve is depressed. The bike starts and runs great but once it's off with the petcock on they leak profusely from between the carbs, covering the engine with gas. The only change I made was to switch from 115 jets to 105s. I did this because I'm switching back to the stock air box, no more pods. The carbs were tuned at a shop a little over a year ago and the bike ran great before disassembly.

What do I do? How do I fix this?

[mystic_1]

There are o-rings on the fuel inlet pipes where they meet the carb bodies.  They could certainly shrink from sitting dry.  They may swell back up over time now that they're being exposed to gas again.  Replacing them involves disassembling the carb rack, sadly.

mystic_1

[nobody]

That's the answer I feared. Maybe I'll just leave them sit for a few days, occasionally giving them a little bit of fuel and hope they swell up and reaseal.

Is there any other possible reason they'd be leaking from this area?

[CB750Winger]

  The o-rings on the fuel inlet T-tube or pipe could very well be cracked like mystic said. There are two o-rings on each side of the tube. I got an assortment of metric o-rings from Harbor Freight for around $7 and pretty much has any size for the bike. It's not that bad to pull the carbs off and replace them. When you get them off, all you need to do is loosten all the carb plate mount screws in the front enough to get #1 & 4 carbs away enough to get the tubes out. It will give you piece of mind on the fuel leak.

[ekpent]

Here are some flea-bay ones from TAS-Pretty nice folks.   http://cgi.ebay.com/ebaymotors/Honda-CB750-Carb-Connector-Tube-O-Ring-Kit-CB-750-SOHC-_W0QQcmdZViewItemQQhashZitem27b1736fdbQQitemZ170480857051QQptZMotorcyclesQ5fPartsQ5fAccessories

[nobody]

Thak you guys very much for your responses. It actually appears that I may have started this thread prematurely, though. When I got home last night and flipped the petcock to on, no fuel leaked, not even a drop. I guess those O rings swelled back up and sealed again. So, for now, it looks like I'm in the clear.