V50 Monza

I’m new to this and am a first time Guzzi owner having come over from Morini,s.
I have a 1981 V50 Monza, seems a decent bike but am really struggling with the carbs. The bike wouldn’t tick over so I very stupidly fiddled about with the two screws, all to no avail then noticed a kink in one of the fuel lines, so replaced that. Now the bike at first has a tickover but a bit slow then after a while just races away, also the bike really over revs when you try and change gear, not good at all, especially for any semblance of image I may have left.
I live in Northamptonshire and tried finding a mobile mechanic as I really don’t want to ride it like this.
I would really appreciate any help, I did with the idle screw put it right back then backed it up one and a half turns.

Thanks Charles

Hi Charles, I have moved your post into the tech section, where it was is the area that members advertise services for other members.

My thoughts would be start with basics.
Check the timing.
Check the tank and fuel lines for flow and the fuel is not old.
Make sure the carbs are not full of sediment and the jets are not blocked.
Check that the floats in the carbs work.
Set the mixture and throttle stop screws as standard and as each other.

I hope you get an answer soon.

Thanks Chris
The tank fuel and lines are now all ok, the carbs were meant to have been set when I got it.
I think resetting the screws is best, I know the idle ones default position is full in then one and a half turns out again, but is it the same for the other screw?
You may have a point about the timing as before it was back firing a little, but since I sorted the restriction on the fuel line that seems to have gone, so I assume it was that.
Thanks again


Hi Charles
Welcome to the forum.
The pilot air screw should be adjusted to suit your engine. One and a half turns is a reasonable starting point, but then normally needs to be fine tuned from there by ear to get it running best. There is a second screw that is the tickover adjustment. That just needs to be wound in or out to set the desired tick over speed.
Have you checked the throttle cables are operating freely, a bit of 3 in one oil never does any harm.
Where abouts in Northamptonshire are you? I’m just over the border in Market Harborough, or may be able to suggest someone if you are at the other end of the county.

Hi Charles, have a really good look at the manifold rubbers. If they are at all perished, change them. Air getting in will cause all sorts of running problems including those symptoms you mentioned as the mixture weakens…and eventually damage.


As well as the inlet rubbers check that both carb slides are closing, easy to do without engine running, just open the throttle and let it snap shut, there should be a discernible click as both slides shut together. If there are two clicks then slides are out of sync, if there is only one click from one carb then the other could be sticking and not allowing the throttle to close. With engine running check that moving the handlebars from lock to lock has no effect on the engine revs, if it does then cables need rerouting.
My Monza had one throttle cable sticking which caused all sorts of peculiarities and was only resolved by replacing both cables


Hi Charles,
You do need to work methodically through the procedure in the manual.
I did invest in some gauges (Carbtune). Don’t use it very often but it’s invaluable when there are problems
I am probably a bit far away but if you want to come to Durham (others have) :smiley:

I live just out side Corby, so quite near. Thanks to everyone for the advise , I’m most impressed with the help.


Your not far away at all, about 20 mins so could pop over and take a look if you want. Send me some contact details on a private message if you want.

Hi Don,
Sorry I’m a techno phobe so haven’t a clue how to private message you.


I’ve sent you my phone number. Give me a ring to sort out a time to pop over.

I use a pair of old feeler gauges one in the back of each carb under the slide, so when you slowly turn the throttle you can see them move and then adjust the cables until they move together (not to be done with the engine running!) :unamused:

Don is your man if he is in your area, make sure the kettle is on!

Under the name of the person you want to send a PM (personal message) is the word contact with a speach bubble. Click on that and then there are two icons that drop down, click on the left hand one and that takes you to your messages, it creates a message with a quote to their post. Type in what you want and press send. When they have read it it will leave your outbox and go to the sent items folder. You will be notified when you gat a PM in the top right of the screen (below search) or by email (if you have that set up in your profile) click on the PM icon to read the message.

Best of luck!

All sorted and running a million times better.
The left inlet manifold wasn’t seated quite right and was probably allowing a bit of an air leak. The carbs were tricky to get fitted just right between the rubber & the air filter box, but got there in the end.
It wasn’t firing on the right hand side, I removed quite a bit of muck from the fuel line and carb filter. Once that was cleared she fired up well, tickover and pilot air screw adjusted to about (2 turns out on the air screw) and she was sounding good. Charles came back from a test ride with a big grin and the bike sounded good so all should be well.
It might be an idea to have a look at the plugs to check the colour after another run out and about.
Thanks for the coffee.

Oh yes, the delights of the V50 airbox. I remember them well.
Still, the V50 is still one of the best bikes ever…

Roy Green from the Forest of Dean

Hi again Don,
Sorry about cutting off short , my fat fingers pressed the wrong button. As I was saying it’s so good to have the bike running so well once more, I’m off to get some Vaseline for those stiff side panels as you suggested, I hope you finished your pond and once again many thanks.


Well done Don, a combination of problems, air leak and fuel starvation, not easy to spot without working through the set up thoroughly.

MGCGB membership, buy one get Don free! :smiley:

Spoke too soon. text from Chales, the inlet manifold has moved and not running on the left side now. I suspect rust coming through from the tank is causing problems.

Just a quick update on my Monza, after de-rusting the tank all is well and it now fires on both cylinders. Sadly the sppedo has now stopped so I ordered a new tang from Gutsibits only for the Post Office to loose it and another package, needless to say Gutsibits are now out of stock of the tang so I was wondering if anyone had a spare.



I got one from Nik’s Euro Parts via ebay, or try Reboot Guzzi Spares.
They are repairable if you have both bits to braze together or make a new tang and braze or solder to the disc.