Petcock size

[Tbone4582]

I just bought a new tank to replace my old one.  I have an 81 cb750 custom and the tank I bought was listed as an 82.  Then other night I went to install it and the petcock from the old tank was to small to fit the threads for the new tank.  The bike was not all original so I thought it was an oversight that the tank on it may not have been original so I went back to ebay and bought an OEM petcock for my year tank.  We'll I just got it in today and guess what....same size as the one I already have and still too small for the new tank I bought.  All of the ones I have looked at online look the same.  Where did I go wrong.  I don't know where to get a petcock to fit my new tank or ow to figure out what size I have so I don't order the wrong thing again.  Where there two different sizes made for the 80's cb750 customs?  

[Re-run]

It would be hard to say. Are you sure on the tank years? I know certain years used the same style tank but honda likes to change things. Best I could say right now is to download the manual from a link here and check it out. It should give you some idea.

Maybe 1 of the other guys here will come on and can give you more info. But checkout the manuals section. Some good stuff there, might have your answer plus the shop manual is always good to have.

[woodsrider250]

Pretty sure I read somewhere that the 82 is different.  I know on the K model I have a 79 tank and an 82 tank and they are identical except for the friggin petcocks.

[tbone4582]

Any Idea what size I need for the 82'.  I have it rigged right now but I kills my reserve tank so I have to watch my fuel levels

[tbone4582]

I talked to honda and it looks like the 80' 81' and 82' all have a different size petcock.  I think I have the l think I have the largest of the three and the most expensive.

[Re-run]

Isnt that how it is supposed to work?

I mean the part you really need is the hardest to get and the most expensive!

[mikey440]

 perhaps go to hardware store and buy an adapter that fits in the tank and accepts your petcock, alot cheaper should work and might not even see it, good luck, mikey440

[tbone4582]

I tried that.  The brass fittings in the compression thread section of the hardware store work for the old petcock but the larger size male fitting from the tank has a very small thread pitch and when you step to a size that will fit the brass fittings female end they change pitch to a lager size that doesn't thread onto the tank.

[Jreed615]

I am ging throught the same thing. Kinda. I bought a junk tank off an 82 and kept the petcock and then I got a tank off an 81 and the petcock I have is way to big to fit my tank. I just ordered one for an 81 today. I still have extra pecock if you need.

[Ken]

In reverse/ I gought a nice tank from an "79 to replace the tank on My "81.The other thing that you have also to consider is that the fuel line coming off the petcock on your an "81 or newer  is a larger inside diameter on the fuel line.The older petcock had a smaller outside nipple so it fit too loosely going into the fuel line. Do they make a kit so that a hybrid petcock can be made to fit into the tak as well as the fuel line?

[Jreed615]

I went through the exact same thing. 80, 81, and 82 are all different, I had to order and return 3 of these before I got the right one.. They get bigger as the years goes up. 80 is the smallest and 82 is the biggest. I hope this helps.

[nyraised]

The 461-751 was for the 1982 model year.  It was also used on the 1983 CB1000C, and many of the F models. Also check parts sites for schematics with the OEM number like bikebandit.com

[wackomole]

Do you still have that petcock for the 1982 CB750 fuel tank?
I have an 82 and am looking for that "larger" petcock.
Mine is leaking and the replacement I ordered appears to be for a 1981 (its smaller).

The diameter of the nipple coming out of the tank of the 1982 is about 19 mm.
Thanks,   Herman  [e-mail]