There is a little ball inside the accelerator pump that serves as a check valve. The ball is solid and made out of some sort of plastic that is very resistant to nasty checmicals. I've even accidentally let them soak in carb cleaner only to find no damage. They seem to last forever, but if you need to check yours to see if it has worn, the size should be 3.175 mm or 0.125" or 1/8".

Air box

Print this section

The stock air box could have been designed better than it was. Although a little inconvenient from a maintenance perspective, the real problem is non-filtered air leaks. The rubber boot that connects each carburetor to the airbox deteriorates over time and does not create a tight seal, thus allowing dirt into the engine.

Greg Field provided these instructions to me:

I just silicone the boot to the box. Silicone it, weight the boot with something heavy enough to smoosh the boot's rim to the airbox, and leave the weight in place for 24 hour until the silicone is dry.

These boxes are [very difficult] to install if you don't do it right. The trick is to detach the left carb by undoing the three screws holding the manifold to the head. Put the box in place, worming the right boot spigot over the right carb's inlet. Then worm the left carb's intake into the boot, and tighten down the three manifold screws to affix the carb. Then "wiggle" everything to its best alignment and so there is minimal twisting and puckering of the rubber of the boot. Insert and tighten the three airbox screws. Tighten the hose clamps to the carbs. Also, you may want to mess with the jetting some. I found that 40 pilots and 140 mains worked better than the stock jets. Better gas mileage, too, and no fouled plugs.

I do not like k&ns because I do not believe they filter air very well. They do flow air very well and strain out the big stuff, though. The stock air filter is probly not much if any better at catching grit than the k&n individual elements or single element for the airbox would be. If you hold either up to the light, you can see right through. And the stock element doesn't even get oil to help catch stuff. Unfortunately, there really isn't a better option for the loops (a paper element for the stock box would be ideal), so I ran a k&n element in the stock airbox.

Why the box? It keeps the k&ns out of the sun, so they stay oily longer (really, they do not filter at all if not wet, and 80 percent of the individual pods I see on bikes are dry as a desert) and clean longer because dust and dirt settles on the box rather than the exposed filter. Also, it significantly reduces intake noise. This was important to me.

The airbox may also reduce performance on some bikes. On mine, it seems not to have, though I never did any dyno runs to confirm that. My bike acquired a reputation for going faster than most people really wanted to go, so I'm pretty sure the airbox wasn't hurting me much.

Greg Field's instructions were very helpful when I first installed the stock air box on my Ambassador. Here are a few additional notes from my experience:

When I first siliconed the boot in place, I weighed it down, but not enough. Only the edge got "glued" to the airbox plate and it broke off when I first tried to insert the velocity stack into it. The second time I really weighed it down so that the boot lip was flattened against the plate. I haven't had any trouble yet.
I've found that I can remove either carb without disturbing the airbox (and leaving the boot in place) simply by removing the three bolts that secure the intake manifold to the head.
I've not noticed any performance decrease on my Ambo. On the contrary, I'm quite certain it runs stronger with the velocity stacks than without. I don't believe my air intake is restricted any more with the UFI than with the K&N pods. No data here, just my opinion.
The box does make things quieter...and let's me hear other sounds the bike is making...I like that.

Air filters

Print this section

There really aren't very many choices when it comes to air filters for the V700, Ambassador, and Eldorado motorcycles. As far as I know, we are limited to the following:

Air filters for the stock air box:
- UFI part number MG# 12113600
- K&N part number MG-0100
Air filters that replace the stock air box:
- K&N part number R-0642 - This filter must be clamped directly to the carburetor body...with the stock velocity stacks removed.
- K&N part number RU-2450 - This filter may be clamped directly to the velocity stacks that originally came on the Moto Guzzi Convert, SP1000, G5, and T3 models. Alternatively, the stock velocity stacks may be turned down on a lathe and made to work (I've not done this, but I've heard it will work). If using pod filters, this set up (with the later model velocity stacks that screw right into the VHB carbs) is my favorite. The fit is good, the clamp is secure, the important velocity stack is kept, and the slightly smaller physical size of the filter allows it to fit better in the available space.
- K&N part number MG-2640 - This is a single filter that is clamped directly to both velocity stacks that originally came on the Moto Guzzi Convert, SP1000, G5, and T3 models. Alternatively, the stock velocity stacks may be turned down on a lathe and made to work (I've not done this, but I've heard it will work). K&N lists this filter as a suitable replacement for the 1000 cc G5, SP, and Convert. Thanks to Paul Linn for bringing this alternative to my attention.
- UNI MG-1 - This filter can be clamped directly to the stock velocity stacks.

There is nothing wrong with the stock UFI filter, but it would be nice if a quality generic replacement were available. The "performance" choice alternatives are pretty dissapointing as K&N and UNI filters - although highly touted by their respective marketing departments - flow very slightly better but filter out less than paper filters. For interesting reading, check out:

If you are aware of any additional air filters that fit (especially filters that will fit the stock air box), please let me know by sending an email to greg>at<thisoldtractor.com

Amal carburetor information

Print this section

Contributed by Joe Jump on the Yahoo! Loopframe_Guzzi news group.

Joe describes the Amal carburetors used on the late Eldorado models.

Those Amals are 930's - same stuff used on Nortons, BSAs and Trimphs post 1967-68. The numbers following the dash (after 930) defines the specifics with respect to main/idle jets, slide cut-away and needle taper/position. Don't worry about that - just replace hat you remove with the same parts which have indivual IDs. The nylon screw that broke off in your hand is a bowl drain/main jet acces screw. Parts for these are plentiful. There is a shop somewhere in Florida (Tampa area) called MAP (Made Across the Pond). They will have everything you would need. Do a Google search. And I'm sure you could find the parts in Daytona if you looked in the Yellow Pages.

I run 930s on my Norton. I had the carbs done by AMR in Arizona. Instead of sleeving the slide, they bored the body to accept Mikuni slides which are hard chrome plated brass. You loose the choke but I've found them to be unnecessary with the ticklers. I've put 20k miles on them and they still work great. Amal needle jets and needles are known to wear kinda fast - recommended replacement every 10k miles for precise metering.

One other thing to watch - the float hinge pin can vibrate (British twin) and actually wear an indentation into the bowl gasket. When this happens, the float can buzz around a bit more than normal and cause the fuel in the bowl to splash out through the tickler button and perhaps affect mixture too (too high of a fuel level in the bowl). I had this problem and resolved it by slightly pinching the tabs in the bowl adjacent to the float hinge pin to keep it captive in it's slot.

Lots of people curse Amals. They are simple units and once they are sorted with dissimilar metals between the body and the slide, updated with viton tipped float needles, and the idle jet is opened up/cleaned (bread wrapper twist tie and Gummout spray works great for this), they work good and last a long time. Just my opinion.

Carburetor balancing/synchronizing

Print this section

Contributed by Patrick Hayes on the Yahoo! Loopframe_Guzzi news group.

I presume you have the more common Dell'Orto square slide carbs. There are some early loops with round slide Amal carbs and these comments will be all wrong for them.

I presume you have plenty of slack in the "choke" cables so that they close fully and are NOT hanging off the end of the taut cables.

I presume you have vacuum tap ports on your intake manifolds. Again, early loops did not have these ports. They can be added easily. Later loops all had them.

I sure hope you have some form of vacuum measuring tool. Forget about doing it by ear, or feel, or counting rotations before stall, or sticking toothpicks in the carb throats. Those techniques are all horribly crude as related to vacuum measurement.

I hope you do not try to do this with analog gauges. It is impossible. It is far easier to read and far more intuitive if you use vertical column manometer vacuum measuring devices.

I like CarbStix the best, but they do have the danger of spilling toxic mercury. Mine are 25 years old and intact (tap wood). There are modern copies which use steel rods instead of mercury. That would be my choice if I were starting anew. There is an electronic TwinMax. Not as intuitive. But very small and portable as long as you learn how to read it. For about $2 you can make a tool out of fish tank air hose and ATF oil.

Get the bike running and warm and hook up the vacuum.

Begin by setting the idle speed. This is the big, exposed, knurled screw. DO NOT TURN THE SCREW!!! When the slides rest on the pointed tips of these screws there is a lot of contact load. You can damage the screw or the slide. Even for slight adjustments, always crack the throttle ever-so-slightly as you turn this screw so that it is not loaded while turning.

You probably will not have equal idle vacuum readings. They certainly won't be steady as they pulse up and down with each cylinder suction. You can visually and mentally average out where there center positions are. Whichever column is averaging lower, that side is open too far in relation to the other and that cylinder is working harder than the other. Depending on your idle speed, you can choose to slow down the harder working side (and its mercury column will now rise slightly on average) or you can open and accelerate the non working side. It doesn't matter if you choose to open one or close the other, you need to get them pulsing in average parallel. Remember to crack the throttle as you adjust this screw. Counterclockwise drops the slide, slows the cylinder, and raises the mercury column. Clockwise is opposite.

Once you have the idle speeds equal (showing equal pulsing vacuum) you can adjust the mixture. This is the smaller, recessed screw. Turn it inwards clockwise until you hear the motor stumble. Turn it outward counterclockwise until the stumble eases. Back out at least an additional 1/4 turn and maybe even 1/2 turn from this non-stumble point. You want the idles a little bit rich.

Go back and look at your idle speed balance as it may have been altered. Repeat the above two paragraphs.

Now to acceleration balance. Many will write to you about mid-range and high range balance. Hooey!! At big throttle openings and higher rpms, your engine cannot possibly detect minor vacuum imbalances. The place where it is CRITICALLY important is at a stop light or traffic light when you are feathering the clutch and adding throttle to accelerate away. Cylinder imbalance is one of the biggest aggravators of the famous loopframe grabby clutch. It doesn't grab at 75mph, it grabs at 3mph when you are pulling away from a light.

If you did the above idle work accurately, the two carbs are drawing equally at idle and the two cylinders are producing equal power pulses. Now, when you open the throttle it becomes critically important that BOTH sides open and draw simultaneously and both cylinders increase their power output equally. Crack the throttle open. Not a WFO twist, just a 10% crack. Look at the vacuum columns. Just as you crack the throttle, one side suddenly drops or loses vacuum before the other. That side has a tighter cable and is starting to work harder first. Again, you can either loosen that cable or tighten the other.

The effect you want is two equally pulsing vacuum columns at idle and then they both drop simultaneously and equally as you begin to open the throttle. Everything else is superfluous.

You will never get perfection. You are talking lots of sliding parts in the carburetor and the cables and the throttle handle. Its all sloppy stuff and it will look a little different each time you blip the throttle. You will be amazed at how nicely the motor runs when it is in sync and how easily or quickly it goes out of sync. You will soon learn what it looks like to have these columns perfect and also what it looks like to have these columns close enough for everyday smooth operation without being fanatic about it.

Carburetor balancing/synchronizing without carb sticks

Print this section

Even if you don't have mercury carb sticks, you can still do a pretty good job of synchronizing the carbs by hand (both of the following methods are performed with the engine off). And, since the factory didn't include bosses in the intake manifolds to which mercury carb stick could be attached, they expected (and provided explicit instructions in the manual) the carbs to be synced without them.

One method (recommended by the factory) is to put a thumb and a finger into each air inlet and feel when each slider starts to move when you very slowly open the throttle. The goal is to make both sliders open at exactly the same time.

An easier and more sensitive method is to create two 6 inch straight pieces of wire. Place each wire in the air inlet with the end under the slider. The other end of each wire should come pretty close to meeting in the middle. Now, when you open the slider very slowly, you can simply view which wire moves first. Thanks to John Schwartz for this tip.

Regardless of which method you choose, use the throttle cable adjustment screw to synchronize the movement.

Carburetor float bowls - checking for leaks

Print this section

Contributed by John Prusnek on the Yahoo! Loopframe_Guzzi news group. In John's own words:

Another way to test floats for leaks is to put them in the freezer overnight, then submerge them in a cup of hot water, look for bubbles as the air inside expands.

Carburetor - setting them up

Print this section

Thanks to Charlie Mullendore of Antietam Classic Cycle for providing the following information on the Yahoo! Loopframe_Guzzi news group. In Charlie's own words:

I don't use the old "pull the plug wire off" method to set the carbs. Here's the (likely a bit backasswards) way I do it instead:

If you don't have vacuum ports to hook some sort of balancing device to, you'll need to remove the airbox and sync. the carbs by measuring the height of the slides (from the bottom of the slide to the base of the carb throat). You can use drill bits or other similar objects as measuring tools.

As a "base setting", I usually adjust the throttle stop screws (on the square area of the carb body) until there's an approx. 10mm wide (semi-circular) opening showing at the front (towards the engine) of the slide when I look into the carb throat. Measure the slide height at the back (towards the filter) with a drill bit and set both carbs the same.

Make sure you have a little (3 mm or so) slack in the throttle cables where they go into the carb. top. If your throttle twistgrip has a "friction screw" that you can turn in to hold the throttle open, turn it in to do just that. Or if not, figure some other means of holding the throttle open (assistant, duct tape, etc.). Open the throttle slightly and acting on the cable adjusters on the carbs tops, set both slides to the same height. Make sure you still have slack afterwards.

Turn the idle mixture screw (small screw, recessed into the carb body, near the float bowl)in until it seats lightly and then back the left one out 1 1/2 turns and the right one out 1 3/4 turns.

Release the throttle holding device, start the engine and let it warm up. If it's idling too high, turn each throttle stop screw out an eighth of a turn. If too low, turn them in an eighth of a turn each. Try to turn them in or out precisely the same amount to avoid disturbing the balance you set earlier. Next turn each idle mixture screw in until the engine speed drops (listen carefully as it can sometimes be difficult to tell) and then back it out 1/2 turn. If necessary, adjust the throttle stop screws again to achieve the desired idle speed.

Alrighty then. Clear as mud? Best job I can do right now with only 5 hours of sleep last night and after doing some sort of weird triathlon today (ride 4.5 hrs./200 miles to lunch in Keysville, VA, ride 5 hrs./210 miles home, push mow grass for an hour!).

Carburetor - single manifold

Print this section

Tom Short provided these pictures.

Pinging

Print this section