Topic: Anybody got a Nighthawk 650 SOHC? And some calipers?

[coffee_brake]

The 650 forum seems to have reached stalemate on this issue.

I don't have a petcock for my 1982 CB650 Nighthawk. Rather than blow a hundred bucks for a Honda unit, I'm researching aftermarket fitment. I've done away with the vacuum setup and would honestly be happy running an in-line fuel valve and gravity feed.

One-year-only tank, the later Nighthawk 650 tanks are different.

The petcock cross references with several DOHC machines. Part number 16950-461-751.

The question is the tank bung measurements. Mine is most certainly 20mm, with a thread pitch of 1.0.

The folks at Sirius assure me that it's 22mm, because their listing on Ebay says so. But my own stock, original tank is 20mm.

Can anybody put their hands on a Nighthawk 650 tank from 1982, or one of the models cross-referenced, to measure the bung on the tank?

Help would be MUCH appreciated....

[cb650]

If you search the 650 site a few years ago we posted the diff sizes of the 650 bungs. if it is still there anymore. 20mm on  my 82 nitehawk tank.  Some parts sites think cause it is a nitehawk its the same as the 83 but we know better. 

[andrewk]

As far as I can tell from the schematics, the 82 650 Nighthawk doesn't have a vacuum setup, it's a gravity feed with a fuel bowl on the bottom, so what vacuum setup have you bypassed?

I don't think I'd put much faith in what Sirius has to say.  Their information is probably flawed- reading you info straight out of the book they have that has it wrong.

My 2 cents though- buy the stock petcock for 100 bucks.  It'll last another 30 years versus about 3 out of those cheap aftermarket jobs.  And you won't be wondering whether or not it's going to fit.

Best of luck!

[onepieceatatime]

As far as I can tell from the schematics, the 82 650 Nighthawk doesn't have a vacuum setup, it's a gravity feed with a fuel bowl on the bottom, so what vacuum setup have you bypassed?

I don't think I'd put much faith in what Sirius has to say.  Their information is probably flawed- reading you info straight out of the book they have that has it wrong.

My 2 cents though- buy the stock petcock for 100 bucks.  It'll last another 30 years versus about 3 out of those cheap aftermarket jobs.  And you won't be wondering whether or not it's going to fit.

Best of luck!

'81 and '82 had a vacuum cutoff on the carbs, for if you forgot to turn off your petcock.

[trueblue]

I have a fuel tap off of a '79 650Z on the '82 650SC in my shed, just screwed straight in.   

[cb650]

I have a fuel tap off of a '79 650Z on the '82 650SC in my shed, just screwed straight in. 

We cant have things that simple here in the US.   Did you ever post a pic of your 82?

[trueblue]

I have a fuel tap off of a '79 650Z on the '82 650SC in my shed, just screwed straight in. 

We cant have things that simple here in the US.   Did you ever post a pic of your 82?

Not yet, it is not much more than a pile of parts assembled to look like a bike at the moment.  Finances aren't that flash at the moment so nothing will be happening with it for some time yet. 

[cb650]

Sounds like a couple of mine  lol

[coffee_brake]

Thanks for the help.

I'm bringing the bike back to street-worthiness for a friend, and on a tight budget.

If I'm drop a hundred bucks, I'm doing a Pingel. I don't even trust an OEM unit since ethanol fuel.

Mostly I'm getting quite irate at Sirius for not listening to my question. It's not that hard; why can't someone call the warehouse and have the ID of the threads measured for these petcocks that they declare fit this bike?!

[coffee_brake]

I searched a LOT of terms looking for this information before starting a thread. I'll look some more...maybe I've got the wrong terms in there or something.