Air box

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models

Created: 2005 October 28

Updated: 2015 August 19

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 probably 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.

Contributed by Charlie Mullendore of Antietam Classic Cycle on the old Yahoo! Loopframe_Guzzi news group (which has now moved to Groups.io). In Charlie's own words:

I install the boot onto the carbs, position it so that the surface towards the airbox is straight, clean the boot edge with solvent, apply the Ultra Black, attach the assembled airbox to the frame by it's top bolt only - holding it back away from the boot, then swing the airbox down into position and install the two bottom bolts.

I do a dry run first to make sure everything is positioned correctly. Sometimes the top mounting tab needs to go on the right of the frame tab and sometimes on the left. Only when I'm satisfied with how everything fits do I apply the Ultra Black.

Tried doing it once with the cover plate and boot off of the bike and could never get it to fit like it should.