Carb velocity stacks Quiz

My old Ambassador is now up and running.
Under the black boot thing which connects the carbs to the air box, each carb has a sort of velocity stack screwed in. As with nearly everything on this ‘Triggers broom’ of a bike, nothing seems right and they are diferent on each carb. Is this right? If so which one is located on which carb. Also the carbs were set up really oddly. Left hand size 145 main and 50 pilot same on the right but the slides were different 6 on the left 4 on the right. 5 onboth sides now and running 130 main and 45 pilot. Still runs a little rich but I’m a bit nervous about running any leaner as I just spent the nation product of a small country on the barrels.

No experience of the loop frames myself, but it is quite likely one is longer than the other as the left cylinder sits further back than the right one so different lengths is likely to reach the air box.

Not sure how it may apply to Ambassadors, but I have seen this sort of thing before. Where there’s an air filter box, each carb has a little bit of tube or ‘velocity stack’ added to it and sticking back into the interior of the air filter box, and they are different lengths on purpose. Can’t remember the details but it’s usually about straightening out the power or torque curve. So, some people think they can be clever and junk the air filter box altogether, or cut holes in it, or change to pod filters or do something else, to get more bhp, and yes it does, at ONE engine speed (at the top of the rev range usually), BUT it sacrifices ponies in the mid-range or lower, so real world performance is actually worse, and the power curve can get quite lumpy. In other words, the manufacturer has already been down this path, and what they ended up with is what works best …

I’ll try and find a picture of mine, but have you tried the on-line parts books to see what the part numbers are? You can get them in a few places e.g. Teo Lamers, Stein Dinse.

As Don said it is because the left hand pot is further back (shorter inlet duct) than the right. This is because the main bearings are one behind the other on the crank shaft, and in my opinion has nothing to do with torque curves on a low tune engine on a touring bike.

Hi David, assuming that your motorcycle is a V750 Ambassador then the two air intake tubes should be the same part. They are part number 12 11 44 01. The one on the left in your photo looks like the correct one to me. As many have pointed out the cylinders are displaced with the right hand cylinder being forward of the left. In the case of the air intake tubes this difference is taken up by the rubber connector to the air filter box. The right hand rubber stub is longer than the left hand one.
The air intake tubes are very scarce parts, and difficult to find. It took me some time and a kings ransom to find the pair I needed for my Ambassador.
Hope this helps, Phil

Phill you are spot on, the parts are identical (number 11) and the rubber sleeve (number 67) is eccentric. If you used the two you have you would have to cut the rubber sleeve to suit.

Thanks all for the reply.
Phil, Chris, I think your right as the black boot never seems to fit right. The stack on the left of the photo is the one that’s right and it has a concial run in. The one of the left has a straight internal path. On the bike this one always runs rich. Next question Has anyone got one for sale. Otherwise I might try and machine it as near as I can to match the other. Thanks again for the help.

If you do a Google search for guzzi 12114401 it brings up a few options…
Ducati Paddy shows a pair on the website, assuming it is up to date