V65C carburation issue

I bought a Motoguzzi V65C but have run up against carburation problems , I replaced the old airfilter with K&N type airfilters from Gutsibits it would not run right with 105 main jets and so I fitted 115 main jets this did help but it’s still not right with backfires through the carbs , and sometimes it feels as though it goes onto one cylinder but as soon as I engage the choke it responds immediately and pulls well however it soon resorts back to poor running.
The carbs have been cleaned in a sonic bath but made no difference anyone ever experienced this and how did you cure it.

Not an expert by a long way but it sounds as if it’s running weak. Try raising the Needles a notch as I think this affects the mixture at intermediate throttle openings.

Or refit the OE air filter arrangement.

Have you tried adjusting the mixture screws on the carb, sounds like they need opening up a bit to richen it up.
Start with the needles on the middle notch and try and get it ticking over,. Start with the mixture screws at 2 turns out then wind them in and out to acheive the best idle speed, then slow it down if necessary using the tick over adjuster,
Repeat for the other side.
I’m not a great fan of ultrasonic cleaners and prefer a tin of carb cleaner spray and assorted pieces of fine wire and a footpump with a small nozzle to blow everything through.

To be honest I’ve never actually used a sonic bath and don’t trust their efficacy, ditto I would prefer to do the clean up “by hand” to be absolutely sure nothing is overlooked.

There could be a few simple things at play here.

How have you fitted the filters? Are they attached to inlet tracts, with the individual filters slid over them or just clipped on at the ends? The reason I ask is that I had a Targa which I similarly converted and it was very sensitive to the unrestricted airflow. I eventually got it right by sliding the air filter over the ‘sleeve’ of the inlet pipes half way. This sounds counter-productive but it prevented a ‘choking up’ at low revs which was present with a more free-flowing arrangement. I concluded that the relatively poor gas-flow (2 small valves) required a restricted intake to maintain velocity through the carb - but who knows?

It was alI a long time ago but I found my old notes; Main jet 135, I had to find a half-way point for needles between 3rd and 2nd notch from the top by using tiny home-made spacer washers. I used a Gunsons colourtune and lots of trial & error but the bike ran well (>100mph and 77mpg on one memorable occasion, mainly 70-ish mpg).

If you can get it to run on a larger main jet, that would be a good place to start.


There’s a bit of information on Greg Bender’s site (This Old Tractor) about the importance of keeping the velocity stacks when fitting K&N filters.
I’ve just fitted the special twin-outlet one to my Spada. This slides over the stacks but was a real swine to fit, considering it’s designed for the job.
Not run it yet apart from starting up to check for leaks etc so no idea if the carburation will need adjusting.

Have you got the float heights correct and the same in the carburettors? If not, nothing will work properly. It is “ground zero” before further adjustments.

Thanks for all the information guys.
I fitted the pod filters because I thought the original airfilter was a pain to work on, prior to this and before I bought the bike it ran just fine.
First thing I did was to increase the main jets from 105 to 115 this did help but still not as it should be the needles were lifted one notch it did help but still not right ,I tried Gunsons colour tune it did not make any real difference .
I found that one of the fuel pipes to the ns carb was bent and restricting the fuel flow, this was corrected and did make a small difference .
I then lifted the needle on to the 3rd notch and reset the mixture with the Gunsons colortune and balanced the carbs again with a set of vacumm gauges that did make the difference I was looking for, no more missing and spitting back although there is still a slight tendency to bog down at low revs when pulling away.
I tried a short run into Newcastle 20 miles and enjoyed the ride with no hiccups so to speak, going for a run tomorrow to see what the economy is like any ideas what I should expect mpg ?

The bikes fuel capacity is supposed to be 16litres but if I put in more that 15 litres I find the fuel will leak out when its on the side stand.
I did 118 miles on a run up to Kielder for a vintage vehicle show good weather and plenty to see really enjoyed it, then we went on to Newcastleton for a bacon buttie , I rode as smooth as possible trying to stick to 50/60mph it went really well no hiccups.
When I was nearly home it did start to miss like it was running out of fuel so turned it on to reserve that settled it down so called for fuel expecting to get poor mileage but I only got 9.9 litres in so 56mpg average not very economical but better than I had been getting.
When I filled up I kept the level down to about 5cm below the filler as I find if I fill closer to the top fuel spills out its the same on my V35ll any one know how to stop it, the rubber seals on the caps appear to be good with no cracks or signs of perishing.
Is it possible to fit a larger capacity tank? if I can any recommendations?

Refuel it while it’s on the sidestand.

Personally I think 56 is good! Wouldn’t sneeze at that.

Bigger tank - not sure there is such a thing to fit this model, and too much of a faff to make fit. All just IMHO.

I have tried that never spilled a drop until I closed the cap , then fuel leaked out of the cap I could not understand what happened unless it was heat from the engine expanded the fuel in the tank but I thought there was plenty of clearance between the fuel level and the cap.
I cant explain it.

Sounds like you’re trying to ‘brim’ it, i.e. fill it right to the top?

I like it full when setting off on a run, but I would not class 2inches off the top as brimming it and was surprised to see so much fuel coming out .
Or is it a motoguzzi quirk and something I have to live with.