Kz750 LTD 1981

[SteveJ61]

I just sent my son home with his first KZ...nice bike, just cleaned the carbs, gave it a tune and it is running beautiful. Trouble is, he's 200 miles away and telling me the bike has begun leaking gas out a tube that falls directly in front of the rear wheel. My first thought was the carb overflow tubes but he says it's not those. He said it seemed to be coming out of a drain line from the bottom of the air filter box. After taking the filter out, he found a small pool of gas in there. Can anybody tell me why gas would be backing into the air filter box? Is there another line that might be bringing gas in to the filter? Thanks for any help.

[sheldonbourgeoi]

Could be a stuck float valve, worn float valve. Float level heights may need to be adjusted as well.

A bad fuel petcock will also let gas past while the bike is sitting, and it will either back up out the carb overflow tubes, or get past the float valves into the cylinders. Then it gets past the piston rings, contaminating the crankcase oil. Can also cause the bike to hyro-lock on start-up, which could lead to a bent con-rod.

[LTD fan]

A bad fuel petcock will also let gas past while the bike is sitting,

That year doesn't have a vac operated diaphragm so fuel will flow unless it is turned to off. Most likely a float valve.

[martin-csr]

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[martin-csr]

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[LTD fan]

His bike has the same vacuum petcock as my 81 KZ650-CSR.

I had a 80 and 81 kz750 and 650csr (Two bikes) and neither had the diaphragm petcock valve. Still have the tanks if anyone's interested.

[SteveJ61]

At first glance at my own 83KZ 750 I thought it was the carb overflow tube also but the tube I believe my son is talking about, and I have two of them, is coming from near the top of the carbs, right in between the two on either side.
Also, I don't believe his bike has the shutoff for the gas line, I might be wrong but if my recollection is correct he does not.