'86 500 tank on '84 500

Hey all, new to the forum. I just purchased an '84 Interceptor 500, and the tank on it was pretty dented up. The guy had a spare tank off of an '86 that was in decent shape, so I swapped them out. The fuel pump on the '84 was faulty, so I just removed it and plan on going with the gravity-fed route. My question is, how do I route the vacuum lines for the fuel petcock on the '86 tank to make it function correctly? It looks like it has two vacuum inlets/outlets on the petcock but I can only find one vacuum line from the motor. HELP!

 

Only the nipple on the very back of the petcock is the vacuum. The one on the bottom middle is a weep hole.

 

So does the one on the bottom need to be capped, or can it just be let open?

 

Open. You can run a drain tube if you want out the bottom of the bike, but you shouldn't need it if your petcock is good.

 

Okay thanks! Now my only issue is getting an adapter to get the fuel line from the tank down to the size of the inlet into the carbs...

 

I ran an 86 tank with 85 carbs on my race bike. I found a y-fitting that had the big size split down into the perfect size of the fuel line into the carbs. I just pointed the capped off one up and the one to carbs down. Worked perfect even under low fuel loads to save weight and full throttle. I think I just happen to have had the splitter in my "junk" drawer. I'm sure you can find a suitable adapter.

 

If I understand you correctly... you dont. You take the vaccum hose and loop it to the atmospheric vent next to it. Then you capp the vacuum port on the left side of the motor.

If you are running gravity fed, you need to do this mod to your petcock... instructions for the vacuum line are in there...

Daugherty Motorsports - Tank Valve Petcock Modification

:hi2:

 

But this tank is an '86, and as I understand, came gravity-fed from factory. The tank has vacuum ports on the stock petcock. I've read the Daugherty modification page, but I though that was only for the tanks that were factory fuel-pumped being switched to gravity-fed..?

 

Do you have pics of the 86 tank? if it's in great shape, I'm in the process of snagging up a clean 84 and would swap tanks with ya.

 

No sorry I don't have any pics at the moment, but I'm eliminating the fuel pump so I figured that it would just be easier to use a gravity-fed tank than to try to modify a fuel-pumped tank to run gravity-fed.

 

I ran mine (86 tank to 85 carbs) gravity feed with the vacuum operation still functional with zero problems. Not to say the mod isn't a good idea, but it's not needed.

And I've ran an 85 tank (vacuum operated) gravity with no problems either. The nice thing about the 86 is it's nice big outlet.

 

Oh... yea I forgot the 86's were gravity.