V50 troubles


I’m Josh from the Cornwall branch of the motoguzzi club (currently living in London) this is my first post on the guzzi forum and sorry its such a monster …

I would like to ask for advice about my recently restored V50 which seems to be fairly ill.

Ill give as much information as i can about the issues and the lead up their occurrence as i can. I should also mention that i am still fairly inexperienced as a both a rider and DIY mechanic but am looking forward to improving in both areas in the near future.

My dad and I restored his old V50 MKII this summer and had it running pretty well. It had a few trips to the garage to totally overhaul the charging system and check the electrics + get and MOT and have a carburation tuneup. We did a full carburetor overhaul using the wonderful guides on thisoldtractor (am i allowed to do that) and gave it our best with the electrics and the cosmetics.

I decided the day after it was all legal to take it from Cornwall to London to live with me at university. This was its first real ride out however since being restored. It had only done short 5-10 mile stints leading up to that trip. A few days after i had arrived in London i started it up and started to ride of, it stalled a few times and i put it down to needing to warm up/bad riding and persisted on my journey. However after 500 meters i realized it wasn’t getting any better, maybe even worse i couldn’t get over 20 mph and this engine thumping laboring was occurring along with jumping uneven revs. it finally conked out when i was trying to escape a bus up a hill at about 10mph coming back home so i pushed the rest of the way.

So summerize - The current problem is as follows: the bike starts and idles OK (perhaps less perfect than it did a few weeks ago right after the restoration) however when you put it under any load it has no power, the revs jump around large amounts at the same acceleration, and you can feel some kind of ‘jumping’ pulsing trauma coming from the bike. It moves but is impossible to ride and when i have been fiddling and ride it around the car park nearby it feels very much like i should be so i push it home …

I have taken of an checked a carburetor which had a minor leak from the inlet and filter area (which seems to still be occurring)

Taken of the plugs and tried to clean them up a bit, they where and are still very black

Checked what electrics i can, pushed in the fuses and checked earthing points that i can find.

Ive asked around wherever i can, a couple of people think it could be carburation, others fuel supply and others electrics and ignition.

I am hoping to ideally solve this problem myself but i have got RAC rescue as an option to get the bike to a garage. But even then i would like to be present when the works are happening or informed of what was wrong so that i get a better understanding of the bike.

If anyone can offer advice, or recommend a good mechanic in the north London area (in N88AE crouch end) i would really appreciate it.

If you made it this far down the post thankyou and i look forward to any responses !

Kind regards


First of all check that the cold start (choke) cables have slack in them. If they are caught up then you will have a super rich mixture all the time. Also worth pulling out the plungers on each carb and checking that the neoprene seat at the bottom is not damaged.

i agree whith brian plus it could be a coil brekin down.

I bought new floats for mine and they both filled up with petrol after a year or so.

Have you checked the oil level, my son had a V50 dint check the oil, it ran low, the bike started but when you tried to open the throttle it had that death rattle from below … hope it is not that mate…

I’m fairly confident the Carburetor floats are ok we checked them both for leaking when we overhauled the carbs. And i would be surprised if the carbs are being problematic as we did a really thorough job of redoing the carbs with new parts for everything that could be replaced new needles and a complete set of o rings.

I didn’t change the fuel filters on the carbs which i assume act as a seal as well. Ive had the one carb apart that was leaking to tighten the fuel inlet (it was the awkward side) This is the circular rotateable inlet on the side of the carb with the ring shanked pipe for the fuel hose.

I will check if the choke is stuck partially engaged …

My oil level is fine at the moment although i can see a little bit on the road under the blow off pipe.

All of the issues we’ve had so far have been electrical, the charging system has been removed and replaced with a simplified alternative (although i cant recall the details) but im not sure about the coils.

Could ignition and coil cause this ‘bumping in the engine’ and general nastyness but still let the bike idle fine?

Cornwall to London on a bike that has just been put back on the road the day previous is a brave first ride!Try taking a plug out, connect it into the cap and hold it on the cylinder head, then turn the engine over as if trying to start it. You should get a nice fat blue spark. If not you have ignition problems. The electronic units can fail on these models but unlikely that both would fail at the same time. They do control the advance retard so might allow it to run at low revs but not pick up power, even one cylinder cutting out would loose you a lot of power.Is it running on two cylinders? Are both header pipes getting hot at about the same time?You mention possible air leaks on the inlet. If they are on the carb to filter bit then this won’t cause too much trouble but a leak on the inlet from the carb to the cylinder head will give you a lot of problems.Have you just filled up with fresh fuel? Water in petrol has been a problem to one or two people lately. Filling with diesel is also bad news and would probably make the plugs black and wet. Is the fuel getting through to the carb OK? Try removing the fuel pipes from the carbs one at a time and running some off into a jam jar, make sure you get a good flow of fuel and then check for water at the bottom.Few ideas to try, let us know how you get on with it.

Did you check the ignition timing when originally working on the bike? Just possible that one of the sensors behind the alternator has worked loose.With these, the air gap is critical,and both must be exactly the same,as it controls the advance point and you can get a flat spot just off tickover.

Are they new plugs also have you fitted new HT leads they break down over time and can give the same symptons
if you have points ignition try replacing the condensor
coils likewise as noted above can fail

have you flushed the fuel tank out and fitted new fuel supply pipes to.the carbs as modern petrol dissolves old pipes and crud in the tank thid could get into the carbs and cause flooding
is the air filter clran and no rags or tools blocking the inlet tract
check battery voltage same symptons if you have a charging fault

Silly question time ~ re that the carbs have been overhauled, are the needles at correct height, or the correct type number even?

I note Brian’s mention about leaking float(s) ~ I was going to mention it but forgot with new floats height always needs double-checking, might be they’re too high (?)

Thanks for the feedback on the problems everyone, ill do my best to try all the other suggestions tomorrow if i can, if not then around the weekend.

I have a good flow of fuel and it looks clean. Ive checked the connection between the carbs and the cylinders and apart from what looks like a little surface cracking they are good and tight. The needles have been set for allowing in the maximum amount of fuel, this was done at the garage after we had set them in the middle notch. they did this in order to get it running correctly saying that modern petrol is now so different the engines don’t run on it so well. This rich running could be why the plugs are black …

In reply to Don-Spada - London was a long trip but it was either that or leave it to never get used for a year back home… the plan was it could save me time and money commuting and taking small trips ralted to my studies … i see now that may have been a romantic idea. As for checking for a blue spark can you confirm that you mean removing the plug from its socket connecting it and then touching it on the rocker box cover (or any other part of the cylinder) while i try to start … this sounds rather exciting … should i not wear a watch for this for example to remove the risk of ARC death ?

For the plug check, take the plug out of the head and reconnect it to the plug cap on the end of the HT lead as it was when in the engine, lay the plug on the head and spin the engine over on the starter. There should be a spark across the end of the plugJust don’t hold onto the plug itself or you might resemble one of those scenes from Casualty.

Don-Spada2012-10-15 23:53:53

Sorry, but I don’t believe all that about modern fuel requiring a much richer mixture. Set everything back to what the book says. My V50 is set to that, and runs perfectly well. Choke size 24mmThrottle valve 40Atomizer jet 260AHMain jet 105Idle Jet 40Easy starter jet 60Taper needle E2 2nd notchFloat 14 gmIdle screw open 1.5 turns.
Brian UK2012-10-16 09:31:41

Older Guzzis are very forgiving of many settings and rubbish fuel. Most run ok on unleaded crap without having valve seat problems.

Go for standard settings and work from there it is far easier that way.