T3 vibes

I appreciate the fact that a forty year old bike with carbs will not run entirely consistently. I rode my T3 from Leeds to Cadwell Park this morning, a distance of about 100 miles, and it seemed happiest cruising at about 60mph, 3,000 revs. On the way back, in the afternoon, it seemed vibey until around 4,000 revs when it was really smooth. So smooth, in fact, that the mirrors were crystal clear. I’m not particularly bothered - I quite like this randomness - but is this normal? It is symptomatic of some sort of tuning issue. The bike is ridiculously low mileage - now 2,400 -is it just running in?

Not ridden my T3 for long enough to notice things like that. Every trip out is a bit of an adventure at the moment.
Have you set the valve clearances exactly right, the timing for left and right side individually and correctly, are the carbs balanced?
If yes to all she should run sweetly, maybe you could have a loosening engine mounting bolt?
Wish mine was running…!

My T3 is a 1978 one, I got it in 1979 with around 8,000 miles on it and was told by most fellow Guzzi club members that 15,000 miles was the general ‘running in’ mileage for the T3’s etc. yes that will sound odd these days but that the way it was back then.

Below a certain rpm you will get some ‘vibration’ which is actually the individual power strokes of each cylinder with a time delay in between long enough to make them noticeable. Apart from correct setting up already described other causes can be running too lean (jets partially blocked) and ignition timing too advanced, but doesn’t seem those apply here if OK at 4k.


As northwest (that fine balding fellow) says it is not run in.Once you get to 10k you will find that after you have warmed it up it wants to run higher revs and will ve smoother lower down once you have given it a blast early on in your ride.My '02 lil’Breva is exactly the same.The smooth mirrors are normal imho. T3’s out accelerate lemons up to about 35-40 mph due to the smaller carbs, then the bigger lemon carbs take over. Discuss

Yes I can see that and would agree (if no-one else can)

I spent a lot of money getting my engine internals dynamically balanced at Basset Downs and I balance the carburetors with vac gauges. It is smoother than it was before I rebuilt it but it still vibrates at certain engine speeds and the vibration is always stronger when the engine is pulling under load.

It’s just a characteristic (flaw) of the engine design unfortunately.

You will probably find that the change in vibration you describe is down to the amount of throttle you were using at different stages in your journey.

Well my bike before my lemon was a Ducati 250 mk111 so Guzzi vibration is minimal compared.

I actually like the T3 vibes. Way back, I used to ride a Z1000 which was beautifully smooth but was completely without soul. A superbly engineered washing machine on two wheels. I find it interesting that the T3 varies from ride to ride. On golden days it seems smoother and more powerful than on others, and the Lafranconis make a deeper, crisper sound. I am thinking that it is still awakening after its 37 year incarceration, and tiny bits of debris are still passing through its fuel system with varying results. I am not complaining! It is a joy to ride. It is reassuring that the (proud) engineers of Moto Guzzi built a bike for the long-term that would only reach its best after tens of thousands of miles.

My t3 can vary day to day, but always goes better if I wear ear plugs!

I got my LM crank balanced by Basset Down (twice, as I forgot to empty the sludge trap first time that I sent it… oh how I laughed re-packaging the crank and paying another £50), and for a twin mine is really smoooooth.

Once it gets going, I can just detect a very soft background vibration. As with gtmdriver, carbs are balanced and mirrors clear.

Does this make mine "abnormal?"ReggieV2013-09-30 18:34:12

4000 rpm the Guzzis do tend to smooooth out, depending on which one that is 70-85 on the road

I was thinking of getting hearing aids! The Lanfranconis look like they were made by a man in a shed after several pints but they sound fantastic. I’m looking forward to the day when the baffles finally blow out and the full glorious symphony is unleashed.

Mr Guzzibear - what happens after 4000?

Double check the carb balance and ignition

Mine gets odd vibes below 4000 when it’s out of balance

It goes quicker

I concur, also raising again the issue of partially blocked jets, I guess this is probably same as a mixture imbalance (not very likely the jets on both sides will be partially blocked exactly identically!)

Also well worthwhile checking the float heights are correct and the same both sides.

If you don’t have cross over fuel pipes you can get probs on one side caused by the tap filters

My t5 has been laid up for 15 years or so and needed the tank chemically cleaning

In other words, all the usual suspects

I’ll check all these things, the jets being first. I’ve gone through many tank fulls, and I bet some 37 year old debris has washed out. When I got the T3 the carbs were full of crud. Nigel of NBS had a fine old time cleaning them out.

Thanks Mr Guzzibear for the guidance on what happens after 4000 rpm! I haven’t been past 4000 yet and I wondering whether it got even smoother or got rougher again. I lie. I was really thinking that after 4000 the old Guzzi went to warp speed and I would be in the next galaxy before I knew it.