L-twin engine vibration. Why?

[rktman1]

Before someone flames me, I do like most everything about my 03 LeMans: Handling is great, looks great, ergos are about perfect for me, lovely power band.

 

But why does the V11 vibrate compared to other L-twins? I've owned two other L-twins: VTR1000, RC51, and I currently have an 04 ST4S. These bikes don't vibrate near as much as my V11. Now, these others are all water-cooled, transverse mounted, smaller displacement (1000 cc), and have over-head cams. The V11 vibration is not terrible but I could see where it might be fatiguing on a 400+ mile day.

 

I only have 1700 miles on the bike and it does seem to be getting smoother but the other bikes I mentioned were smooth out of the crate.

 

Once again, I'm not deriding the V11. Just curious.

 

Tim

[Admin Jaap]

I think it has a lot to do with the Guzzi design being 30+ years old.

[pete roper]

I think it has a lot to do with the Guzzi design being 30+ years old.

41348[/snapback]

 

Yes, and there's the fact that there are a lot more reciprocating bits that are heavier in the old pushrod donk. Bore/stroke ratios are different and the secondary inballance factors are probably higher too. To my mind though all of the newer bikes are almost antiseptic in their smoothness compared to my old dungers, (With the exception of the hot rod but thats a super-short stroke motor with a better rod/stroke ratio.).

 

You'll find that making sure the TB's are synced and ballanced properly will make a big difference too.

 

Lets face it the Guzzi motor is almost medieval It's one of the things that gives it it's, (Nowadays.) almost unique charm. Check the tune is right and if you get numb fingers expriment withdifferent bar end weights.

 

Oh! And don't ride it at low RPMs, they much preffer a good thrashing!!!!!

 

Pete

[Lex]

I'll add my suspicion that the Guzzi parts are not well balanced and the transverse layout also contributes.

 

On the first point, anybody actually weight a good number of Guzzi piston/ rings/ rods? I would not be at all surprised to find they are like air head BMWs, lots of variation. Get a well matched set and you get a smooth bike, get a bad set (I've seen BMWs off by an ounce AKA 28 grams) any you get a paint shaker.

 

On the second point, the late, great Gordon Jennings felt that transverse engines seem to vibrate more because the chassis is more flexible from left to right (the plain of Guzzi vibrations) than front to back (the plain of a Ducati, for example) and has less mass to resist the motion we feel as vibration. Jennings wasn't wrong very often.

 

Lex

[Guest Steve_W]

...Guzzi parts are not well balanced and the transverse layout also contributes...the late, great Gordon Jennings felt that transverse engines seem to vibrate more...

Grrrrrrrrrr... Don't get me started...

[Steve S.]

(Lex @ Jan 18 2005, 09:48 PM)

...Guzzi parts are not well balanced and the transverse layout also contributes...the late, great Gordon Jennings felt that transverse engines seem to vibrate more...

 

That's what I was gonna chime in about!

 

Also that since a recipricating force cannot be perfectly balanced by the force resulting from a rotating mass, it's not unreasonable to find that the difference in forces is greater with heavier parts. Oh, and with the exception of that unfortunate "transverse" thing, Gordon was right because the polar moment of the chassis is greater front-to-back than it is sideways.

[rktman1]

Not to pick nits here but I always thought that if the crankshaft was "in line" with the forward-backward axis of the bike then it was called "longitudinal" (like the Guzzi, BMW, Honda ST1100, etc.) and if the crank was perpendicular to the forward-backward axis it was termed "transverse" (Duc, vertical twins, V-twins, every UJM in-line 4, etc.).

 

Someone chime in with correct definition.

 

Tim

[antonio carroccio]

But why does the V11 vibrate

Look it at this way, you do not need the Jacuzzi no more.

Riding a Guzzi is double pleasure now.

[Guest RossGuzzi]

Tell me to go crawl back to the Centauro site, but I recon it`s another reason the factory should develop the 4v 1000. Not to dump the 2v but to have both. The 1000 4v is Smooth!

I know it may be to late, they should have gone for it back in 97-98. Imagine a Rosso Mandello 4v V1000 cc with single sided swing arm and modern grafics (not too modern), headlamp, gauges etc.

I read on another post that the V11 is fairly maxed out as far as engine development goes. I`m sure there is more room to develop the 4v in comparasome. A V1225 Rosso Mandello anyone?

I`m not after R1 power, but just look at what companies like BMW are doing nowdays!

I love the 2v`s but I also love the 4v. I also think there would be more new Guzzi buyers if there were some bikes like described above, being run out the factory.

Easy to say, I guess a lot harder to do!

And If anyone says 'Oh it costs a lot more to make a 4v bike', what is it going to cost them in the long run if they dont?

Regards, & ready for to be shot at!

Ross.

[antonio carroccio]

I don’t know if the selling of Moto Guzzi will go harder with the 4v engine.

When Moto Guzzi made the Centauro and before him the Rs Daytona (I will not mention the Lario) was the selling good enough to survive. Moto Guzzi have never had the aspiration to make big money with his models. That’s why Moto Guzzi is the Moto Guzzi of today.

[Baldini]

....I only have 1700 miles on the bike and it does seem to be getting smoother...

 

My Scura has smoothed out a lot after around 10K miles - exactly same as LM11 did 20yrs ago...The new bikes ain't so different after you get used to em, a bit less vibes, a bit more everything else!

 

KB

[Skeeve]

... why does the V11 vibrate compared to other L-twins?  I've owned two other L-twins: VTR1000, RC51, and I currently have an 04 ST4S.  These bikes don't vibrate near as much as my V11.  Now, these others are all water-cooled, transverse mounted, smaller displacement (1000 cc), and have over-head cams.  The V11 vibration is not terrible but I could see where it might be fatiguing on a 400+ mile day.... it does seem to be getting smoother but the other bikes I mentioned were smooth out of the crate.

 

Once again, I'm not deriding the V11.  Just curious.

 

Tim

41338[/snapback]

 

I don't have the url handy, but there's a nifty site out there w/ some animated graphics of engines & their balance factors/vibratory modes.

 

Here's the deal: V-twins of any ilk vibrate in line with the cylinders [ie, 90deg from the plane of crankshaft orientation.] Harleys, being a narrow-angle twin, vibrate like crazy - over/under/sideways/down; the animation of a 90 deg twin showed almost no up&down but a lot of front to back in the same plane as the cylinders. Net result is that in transverse 90deg V-twins like Ducs & the VT1000/RC51, SV1000/650, etc., the vibration is in the direction of motion & not very noticeable. On a Guzzi, it's side-to-side and therefore much more noticeable than it's transverse brethren. You'll note I said more noticeable, not more.

 

Anyway, that's what I made of it. So sue me if you don't like the explanation...

[helicopterjim R.I.P.]

Anyway, that's what I made of it. So sue me if you don't like the explanation...

41453[/snapback]

Can we really do that?

[rktman1]

Skeeve,

 

I've tried a couple of times over the years to understand the primary/secondary balancing in an engine and from what I've read an L-twin (90 degree V) is supposed to have perfect primary balancing but not so good secondary balancing. I believe the primary balancing concerns the mass in the pistons, rods, and crank and the secondary balancing is the mass in remaining moving (engine) parts. I could be way off-base with this. It was many years ago whan I made my last attempt to understand it.

 

The fact that the MG is a longitudinal mount (vs transverse) makes sense in the balance equation though, as far as it being more pronounced.

 

Anyway, I like the LeMans - rode it to work today. I call it my "new old thing".

[Guest Steve_W]

Not to pick nits here but I always thought that if the crankshaft was "in line" with the forward-backward axis of the bike then it was called "longitudinal" (like the Guzzi, BMW, Honda ST1100, etc.) and if the crank was perpendicular to the forward-backward axis it was termed "transverse" (Duc, vertical twins, V-twins, every UJM in-line 4, etc.).