Old ambassador fuel petcock issue

[ampm7]

I have a 1970 Ambassador and was wondering what the proper positioning is for the fuel petcocks. I rode the bike for 2,000 miles before it blew the right side piston (facing forward as seated). I changed to Gilardoni's and it was working good just not working in 3rd and 4th but that's another story. I had originally been using the left side fuel petcock in a down position and the bike worked quite well. Is the metal crossover in the fuel lines able to mix fuel for both carburetors or not? It seems to me like on my old Triumph that the left side was used for the reserve as your throttle hand did not have to leave the throttle. How do you guys do it? When I put the right hand petcock in a down position it floods the carb and comes out the velocity stack. I really don't like these petcocks and they are 2 years old because they never completely shut off! I bought them from MG Cycle which is awesome but...I also inspected them and the o-rings are fine. In other words what is the correct positioning for run mode on the Ambassador? Charlie if you are out there, I tried to find Yahoo loop frame forum of which I was a member a few years ago and then I had a major problem with accessing the forum and gave up. If you can send a link it would be greatly appreciated.

[Kiwi_Roy]

I have an Eldorado with the sugar cube style petcocks (original with parts from John Chicoine)
John supplied filters that have different length stand-pipes to allow for a reserve.

I only ever open Left side but with both sides open it will not flood, I suggest you have a bad needle valve or float has sunk.

Using the left petcock as reserve makes sense but I close it before I arrive back home, I prefer doing that with my left.
The only time I ran out of gas I found both open, if it starts to cough easy enough to open the right before it dies completely.

Might I add a link to John's latest offerings
https://ibb.co/mQnSby
https://ibb.co/bzstGy
https://ibb.co/jU8did
https://ibb.co/kYADGy

[yogidozer]

correct position for run?
disconnect the fuel line, check flow in each position, also check to make sure it stops, in the stop position.

[guzzisteve]

On my V700 I have MG cycles taps.  Same as Ambo/Eldo where down is on, back is reserve, forward is off on left one. Right one is opposite, back is off , down on, forward is reserve. Same petcock on both sides not a L & R.

[Antietam Classic Cycle]

The Loop Group: https://groups.yahoo.com/neo/groups/Loopframe_Guzzi/info

As has been posted, disconnect the  hoses and operate the petcocks to determine which way is off, on and reserve.

If both petcocks have a reserve position, then I run with both open. If they are on-off only, then I use the right as my main supply and open the left when reserve is called for.

As Kiwi Roy posted, it might be time to replace your float needles (new ones have orange-ish tips) and check that your floats aren't filling with gas. 

[Chuck in Indiana]

How many times do I have to post this?  Don't use those crossovers. I lost a fine V700 because of them.
001 by Charles Stottlemyer, on Flickr
You don't want to know what happens if one of those very lightly swaged hoses comes apart, pours fuel on the tire, and you start into a corner.
Use dual banjo petcocks instead. Trust me on this.

[Antietam Classic Cycle]

How many times do I have to post this?  Don't use those crossovers. I lost a fine V700 because of them.
001 by Charles Stottlemyer, on Flickr
You don't want to know what happens if one of those very lightly swaged hoses comes apart, pours fuel on the tire, and you start into a corner.
Use dual banjo petcocks instead. Trust me on this.

Not all of them are made like that Chuck. That wasn't original on a V700 either. The original V700 part was a square of steel with four inlets soldered into it and it bolted to the top of the breather box.

There's really nothing wrong with that style metal crossover either if the hose is replaced. Dual-inlet banjos aren't always easy to plumb in, especially when the original airbox is used

[Rod]

MG Cycle sells 2 crossovers, "economy" fabric wrap, and "best quality" rubber. Cheapskate that I am I went with economy and it immediately started leaking. Bought the rubber for both my Ambo & Eldo and they are fine.

[Rod]

I've always been curious about the reserve petcock setup. My 70 Ambassador has both sides with only open/close options, there is a "C" on both sides (no circle), clear enough. Then I took a set off my Eldorado, and one had "C" on both sides in a circle, and the other had "C Riserva" on both sides. The pipe on the Riserva rusted off, but I guess perhaps the pipe was shorter than the "C" petcock, so that's how it gave you reserve. My new "sugar cube" petcocks from MG Cycle both have a true open/close/reserve functionality, which I believe alters the level that fuel can flow into the pipe.

Somewhere I saw a claims that with those new petcocks you can actually have 3 reserves. But I'm not so sure. When my Ambassador (2 open/close) ran out and I tried switching over, I promptly ran out again and had to push about a half mile to the gas station. So if the level is low on one side, it seems the gas would find the same level on the other, assuming you hadn't leaned the bike too hard??? Needless to say I've never tested it again since. Maybe that was a refit on my old Ambo and someone should have put a Riserva on the other side.

[Antietam Classic Cycle]

MG Cycle sells 2 crossovers, "economy" fabric wrap, and "best quality" rubber. Cheapskate that I am I went with economy and it immediately started leaking. Bought the rubber for both my Ambo & Eldo and they are fine.

I don't trust the hose on either. There's a reason I use the lemon yellow Tygon hose...

I've always been curious about the reserve petcock setup. My 70 Ambassador has both sides with only open/close options, there is a "C" on both sides (no circle), clear enough. Then I took a set off my Eldorado, and one had "C" on both sides in a circle, and the other had "C Riserva" on both sides. The pipe on the Riserva rusted off, but I guess perhaps the pipe was shorter than the "C" petcock, so that's how it gave you reserve. My new "sugar cube" petcocks from MG Cycle both have a true open/close/reserve functionality, which I believe alters the level that fuel can flow into the pipe.

Somewhere I saw a claims that with those new petcocks you can actually have 3 reserves. But I'm not so sure. When my Ambassador (2 open/close) ran out and I tried switching over, I promptly ran out again and had to push about a half mile to the gas station. So if the level is low on one side, it seems the gas would find the same level on the other, assuming you hadn't leaned the bike too hard??? Needless to say I've never tested it again since. Maybe that was a refit on my old Ambo and someone should have put a Riserva on the other side.

The one with just the "C" on both side should have a "standpipe" approx. 40 mm long inside the filter screen. The "C Riserva" one should have no standpipe at all. So, when the fuel level gets down past the pipe on the "C" petcock, the "C Riserva" will still have some fuel to draw from.

[Rod]

Well no pipe in the Riserva makes perfect sense, but I definitely have a broken off pipe in mine for some reason. So I think I'll put that one on the left side of the Ambassador this winter as a proper reserve.

[ampm7]

When I put the bike back together after installing the new cylinders/pistons and since I had taken off the tank I marked the tank with the correct markings that are on the petcocks. Closed, open, reserve. The right and left are the same in only one way in that down is "open". However, closed and reserve are opposite from left to right side. Since I had left the bike sit for some time, I removed the carbs and rebuilt them (again). The unfortunate thing is I thought I had kept the original floats but somehow they have gone missing. So, I replaced them with the new white ones but I did alter them somewhat and that might have been the problem with them leaking. So, I ordered some more and installed them. They are not leaking now. The problem I have is that the spark is very weak from the coil. The coil was replaced by Cyclegarden (Bosch blue) as I had unfortunately cracked the the top black cover trying to remove the spade connectors on a Bosch blue that I had bought so that I could use ring terminals with the previous wiring harness. It still worked but didn't pass Cyclegarden muster. I have since replaced all the wiring with Greg Bender's wiring harness. Everything works, turn signals, horn, lights, clean wiring in the headlight bucket, starter etc... My thing for today/night is to pull a spark plug, ground on the cylinder and see what kind of spark it is displaying. It is very weak at the points but does show some spark. Then if it is a weak spark I am going to run a wire directly from the ignition "on" switch to the + side of the coil bypassing the resistance of the handlebar mount starter button. This is my third Moto Guzzi and unfortunately I have had problems with them. This is a simple bike and it should run well...Thanks for your input.

 

[Kiwi_Roy]

Welcome to the forum AMPM7, if your spark is very weak perhaps try a new or different old condenser, there was a time when you got no spark at all from a coil without one.

[ampm7]

I replaced the one that I had on there with a new one and then changed back to the Mallory which was also a fairly new replacement. The trouble is with condensers (electrolytic) is that years ago when condensers were used on all the cars they were new but nowadays since they are not new how long have they been on the shelf? From my past experience in electronics, condensers/capacitors have a tendency to crystalize. I saved the other condenser and will put it on after my experiment tonight. Thanks