Modern Vespa

Silly question of the week?

Is this normal, a quirk with my bike ,or...

If normal why?

Yes it's normal.


FAQ: Why does the engine sound different with the brakes on?

Well silly me.

There IS more load on the engine, when the brake light goes on. Presumably, with a good battery, the change is slight, presuming the stop is short-term, but still there.

Content deleted by tenders. A forum where management/moderators repeatedly quash and delete well-intentioned, constructive concerns about governance issues raised by multiple users does not deserve my participation.

I don't believe it is an electrical load issue, but mechanical. When the engine is idling, there are certain harmonics and vibrations throughout the various parts. When the rear brake is engaged, shoes or pads, that creates a stiff-hitch between the swing arm and the drum or rotor, thereby changing the harmonics.

To an old retired engineer like me, that sounds like the most plausible explanation. Anything you do to stiffen or loosen the coupling between all the vibrating parts of the scooter will change the balance of the harmonics that make up the overall cacaphony.

Today's exercise is to see if applying the front brake alters the tone of your Vespa.

This.

On the 250 the rigid link makes the whole bike shake as well.

On our GTSs the front brake doesn't change the idle, but when we engage the rear, the idle speed increases.

No it doesn't. The higher harmonics (mostly 2nd and 3rd) of the frame vibrations are louder, so it *sounds* a higher speed - but if you had a rev counter you'd notice zero change.

Had an old Airhead BMW with a voltmeter. You could see a bit of a drop on the voltmeter when the brake light came on. But then, the alternator on that bike didn't make much power at idle, so you were running on battery voltage at idle. I expect our scooters are better.

Blummin heck.

It's as above.....mechanical.

Revs don't change either.

Front brake is too remote/distant to create the extra vibration.

The rear brake is right at the engine, you apply it and your removing any/most damping you had between you and the floor.
So you'd notice a small amount extra vibration.

Simples

BV350 has a volt meter and voltage drops when brake is applied at idle too. From 14.0 to 13 or 13.5

+1

The Mechanical guys blame it on the electrical. Electrical hardware guys like me say it can't be electrical, has to be a software bug. Then the software gurus blame it on Social Engineering. In the final analysis it's due to operator error!

Iiiiiiittttttsssssss mechanical. Even if the revs did raise or drop it wouldn't make the bike shake more.

Put it another way. Apply the rear brake and try and bounce the suspension......it's either impossible or travel is reduced.....thus the vibration is sent through the shock and into the frame.

Simples (with an eastern block accent)