Fuel petcock sizes?

acadia81 · Post by **acadia81** » Wed Feb 20, 2008 10:38 am

So my '82 CBX is almost finished, I take the NOS tank out of the Honda box to put it on the bike and the original fuel petcock won't fit, the nut on the petcock is too big.
As best I can tell, the fitting on the NOS tank is 18x1.00mm, the original tank fitting is 20x1.00mm. Both tanks are '82 white tanks.
I have an old '81 tank that is also 18x1.00mm, but no petcock.

Does anyone know if there is a bushing or adaptor available to mate the old petcock to the NOS tank, I couldn't find anything locally.
Or do I have to buy a new petcock?
Would the adapter nut for a Pingle vavle work?

Thanks for the help.

gnuse · Post by **gnuse** » Fri Jan 01, 2010 3:01 pm

Always wondered why Honda changed the petcock for 1982.

Jeff Bennetts · Post by **Jeff Bennetts** » Fri Jan 01, 2010 3:45 pm

If you do find an adapter nut to work your reserve will be reduced greatly because now the petcock tube will sit lower in the tank, thus reducing the volume of gas available when you switch over to reserve.

No biggie just be aware.

daves79x · Post by **daves79x** » Sat Jan 02, 2010 6:28 am

All stock '82 tanks had the larger opening, requiring the larger petcock. All other years were the smaller one. You say your tank is NOS Honda. Are you sure? Not saying it isn't possible, but I've never seen a small-petcock '82.

No matter, you still need a petcock. There are lots of good, rebuildable ones available, although most are '79s with the smaller outlet (1/4 vs 3/8). You can still get the rubber packing for those ones.

You see new ones on eBay often, but I'd check that they were '80-'81s with the correct outlet size. Maybe a Pingle is the way to go.

Dave

daves79x · Post by **daves79x** » Sat Jan 02, 2010 6:44 am

Just an update - it seems that the '79 and '82 petcocks are still available from Honda, but the '80-'81s are not. You can use a '79 one - the standpipe is a little lower (less reserve) and the outlet is smaller, but if you clamp the fuel line well, you can use the stock Honda line or new 3/8. You could also ask around for an '80-'81 to rebuild. Sorry, I don't have a spare. Good luck.

Dave

alimey4u2 · Post by **alimey4u2** » Sat Jan 02, 2010 7:50 am

According to Pingle, The 79-81 had a 18mm thread whilst the 82 had a 20mm. The Pingle Power Flo valve is 1/4 male NPT, hence the need for the adapter.