Petcock use on old Ambo

[ampm7]

I have a 1970 Ambassador and just put new petcocks in and want to know what is the proper usage of them. Both on at same time, right or left on separately; as it seems when I use both of them the left cylinder gets too much gas. Charlie can you chime in? Thanks

[Antietam Classic Cycle]

Do the new petcocks have a reserve position? If so, I'd run with both on. A word of warning: several of my customers have had issues with the new square petcocks: the rubber seal inside rotates and restricts fuel flow and/or won't stop fuel flow when they're off.

 

[ampm7]

Charlie, I took off those square petcocks as they would not fully shut off. So, if I left the bike on the side stand the left cylinder would flood over a period of time and when starting would foul the plug plus, it probably put gas into the cylinder. I got the later ones that MGCycle sells which need to have the strainers removed before they can be inserted into the adapters. They work quite well as they don't leak and they are the same orientation on both sides. So, you are saying to keep both open at the same time?

[Kiwi_Roy]

I resurrected the original square ones on my Eldorado I only turn one on and the other acts like a reserve.

[Antietam Classic Cycle]

Charlie, I took off those square petcocks as they would not fully shut off. So, if I left the bike on the side stand the left cylinder would flood over a period of time and when starting would foul the plug plus, it probably put gas into the cylinder. I got the later ones that MGCycle sells which need to have the strainers removed before they can be inserted into the adapters. They work quite well as they don't leak and they are the same orientation on both sides. So, you are saying to keep both open at the same time?

Okay, you bought the V65 type petcocks and adapter kit? With those, I run both open at the same time as long as you retained the main supply "standpipe" on both.

[ampm7]

Yes, it has the "X" fuel mixing metal fitting on the fuel lines as original.

[Tom H]

I have wondered about this for the last 40 years. I have always just run the right side so I could keep my hand on the throttle while opening the left. I think both Loops ran fine this way?

Charlie,
Are you saying that the V65, as you called them, vales do not deliver enough gas with only one on? What about the sugar cube with reserve?

Thank you,
Tom

[Antietam Classic Cycle]

Yes, it has the "X" fuel mixing metal fitting on the fuel lines as original.

By "standpipe", I mean the plastic "straw" through which fuel flows when in the "on" position. If you don't retain the standpipe you'll have no reserve.

Charlie,
Are you saying that the V65, as you called them, vales do not deliver enough gas with only one on? What about the sugar cube with reserve?

Not at all! I'm just saying it really makes no difference with any petcock that has a reserve position. Run with one open or both open, really makes no difference as long as the carbs get adequate fuel supply. Of course, a crossover or dual-inlet banjos must be fitted for this to be true.

Some original petcocks were on/off only and one usually had a standpipe and the other didn't. The one with no standpipe was the "reserve" petcock and was usually installed on the left side of the tank. They were marked "Riserva". That way, as you wrote, one could keep the throttle open and flip the reserve on with their left hand.

Later, some original petcocks had on/off/reserve. At this point, the rider could turn both on and when reserve was needed turn both to reserve. Or just run with one open and have a larger reserve. These are marked with a "C" on one side (closed) and "R" on the other (reserve).

The update kit that MG Cycle sells has two (small-block) V65 petcocks with on/off/reserve. Same as above. the rider can turn both on and when reserve was needed turn both to reserve. Or just run with one open and have a slightly larger reserve.

[Dave Swanson]

And by the way, John Chicoine does a great job of rebuilding the original petcocks. 

[Chuck in Indiana]

I have wondered about this for the last 40 years. I have always just run the right side so I could keep my hand on the throttle while opening the left. I think both Loops ran fine this way?

Charlie,
Are you saying that the V65, as you called them, vales do not deliver enough gas with only one on? What about the sugar cube with reserve?

Thank you,
Tom

Yeah, that's what I do, too. Out in SoCal you don't want to be reaching down with your right hand to turn on reserve. As you are slowing down while fuel runs in the carbs you'll get run over by a 3 ton SUV running 90. 

Yes, it has the "X" fuel mixing metal fitting on the fuel lines as original.

Make absolutely sure the crimp connections are secure. You may be able to just pull them apart. They caused my infamous crash and burn.

[Tom H]

Charlie,
AFAIK, they have had enough gas to run properly at freeway speeds. They both started out with the on/off sugar cubes. Upgraded the Ambo to the on/off/res cubes and the Eldo to the V65 setup with adapters.

My Ambo has been upgraded to roundfin 1000 complete engine , VHB30's, Ambo dist.. Maybe I should try both sugar cubes open and see if it makes any difference. It "seems" to run fine fuel wise down the freeway.

Thank you!!!!
Tom

[Kiwi_Roy]

And by the way, John Chicoine does a great job of rebuilding the original petcocks.

+1 He sold me a couple of kits that I used to restore my sugar cubes, they give tight shutoff and zero weeping.

[ampm7]

I left the standpipes in as instructed.