Differences in gas tanks

[Alex_V]

Quick disclaimer - I had at least 5 Hawks over the years and swapped parts without any issues.

I managed to get a brand new red tank for my Hawk project. Went to swap gas caps, just to realize the old cap wont fit the new tank. The front notch in the cap goes into a small opening in the old tank, while new tank's opening is perfectly round. So I can either try to put a small bend in the opening of the new tank, or grind down the notch on the cap.

Anyone ran into such difference in tanks?

[6]

Nope.

[ParcNHawk]

Vented vs non-vented tanks. This is the California emissions equipment vs the 49-state (or rest of the World.)

The Cali tanks have an addition nipple on the underside from an internal vent. It normally vents (via other associated equipment) to an intake feed or eventually a charcoal canister to keep fuel vapors from getting to the open environment.

The non-Cali tanks have no such internal vent. They have a fuel outlet and filler lip drain as the only nipples on the underside. In this case, venting is done through a small opening in the fuel cap and allows vapors to escape into the free air.

In order to keep Cali tanks from free venting vapors, the vented caps will not fit the internally vented Cali tanks.

Venting is essential if you want to ride for more than a couple of minutes.

So... what tank do you have?

[ParcNHawk]

So I can either try to put a small bend in the opening of the new tank, or grind down the notch on the cap.

Making the cap fit might not mean making the cap work.

A vented cap on a vented tank will function.

A non-vented cap on a non-vented tank will cause fuel flow issues.

A vented cap can be identified by a little black valve on the underside while a vented tank can be identified as having a fuel outlet (petcock) a large bore (but smaller than the fuel outlet) water/spill drain AND a (I want to say) ~⅛" vent nipple. A non-venting tank lacks this smallest nipple.

[ParcNHawk]

[69Falcon]

I ran into this with the Revere tanks, they don’t have the little notch either. I run a cap from gascapdude.com

[ParcNHawk]

Without having my Hawk here or a parts cache I can't advise on what to do BUT I did use a vented CBR tank with a cap with the extra casting on that tank. It initially didn't fit so I pounded it down with a big rubber mallet to dent the tank do it would fit. It worked.

If the OP had a Cali tank then it's fair game to do that.

[Alex_V]

Thanks for a detailed explanation. Appreciate it.

Looks like I am trying to fit a vented cap on a Cali tank. Way to make things easier - California.

I think I will do the mallet hitting idea. My usual way of fixing things.

If anyone needs a non-dented, non vented tank, I would be looking to trade for a aftermarket exhaust.