OP
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GTS Supertech 300
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Location: Southwest Florida USA
 
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I have noticed on my 2023 GTS Supertech 300 when the rear brake lever is pulled that the engine loads up under a strain and there is a slight vibration. Anyone have any idea why?
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'23 300 Super
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@armedferret avatar
'23 300 Super
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mine does it too. i just assumed it's a power-assist off vacuum or something that causes just a tidge of extra load at idle.

hasn't caused any issues (at least not yet), so i can't imagine it's a major thing.
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Molto Verboso
Vespa GTS 300
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Molto Verboso
Vespa GTS 300
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Do you mean that when you pull one/both brake levers while stationary, the noise changes and slight vibrations may occur?

Then this is absolutely normal. Pulling the brake creates a frictional connection, the noise changes and vibrations from the engine can be transmitted (differently) to the body via the brake, brake caliper, chassis, etc. When the brake is released or applied, the path of transmission of the vibrations changes / the "oscillating" mass changes.
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2007 Vespa GTV 250ie
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@gunnut37086 avatar
2007 Vespa GTV 250ie
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UTC quote
GermanGTSDriver wrote:
Do you mean that when you pull one/both brake levers while stationary, the noise changes and slight vibrations may occur?

Then this is absolutely normal. Pulling the brake creates a frictional connection, the noise changes and vibrations from the engine can be transmitted (differently) to the body via the brake, brake caliper, chassis, etc. When the brake is released or applied, the path of transmission of the vibrations changes / the "oscillating" mass changes.
Like the OP, I interpreted the vibration as load/strain on the engine, but was told it was normal.

However, I was never told why. Your answer is very interesting, I never thought of that. Thanks
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Gigi, '13 GTS 300ie Touring
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Gigi, '13 GTS 300ie Touring
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GTS300 Super 2015 Blue, GTS300 Super 2023 Beige
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UTC quote
When the brake is applied, the pressure in the brake line forms a "solid" connection between the engine and body allowing the vibrations to get through, bypassing the suspension.
OP
UTC

Member
GTS Supertech 300
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Location: Southwest Florida USA
 
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GTS Supertech 300
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UTC quote
GermanGTSDriver wrote:
Do you mean that when you pull one/both brake levers while stationary, the noise changes and slight vibrations may occur?

Then this is absolutely normal. Pulling the brake creates a frictional connection, the noise changes and vibrations from the engine can be transmitted (differently) to the body via the brake, brake caliper, chassis, etc. When the brake is released or applied, the path of transmission of the vibrations changes / the "oscillating" mass changes.
Only while the handle for the rear brake is pulled while stationary. Doesn't do it when the front brake only is applied. It's not causing any problems, I just thought it was odd that it done that. The dealer never noticed one doing it and didn't have a clue why it does it.
OP
UTC

Member
GTS Supertech 300
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Location: Southwest Florida USA
 
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GTS Supertech 300
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UTC quote
Mike Holland wrote:
When the brake is applied, the pressure in the brake line forms a "solid" connection between the engine and body allowing the vibrations to get through, bypassing the suspension.
I never thought of that as a possibility. Very interesting and a likely reason.
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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MrTaz wrote:
I never thought of that as a possibility. Very interesting and a likely reason.
It IS the reason. The suspension becomes locked by virtue of the brake being applied, and the amplitudes of the harmonics of the main engine frequency alter relative to one another.
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1980 Vespa P200e (sold), 2002 Vespa ET4 (sold), 1949 Harley-Davidson FL
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@caschnd1 avatar
1980 Vespa P200e (sold), 2002 Vespa ET4 (sold), 1949 Harley-Davidson FL
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Location: Sparks, Nevada, USA
UTC quote
GermanGTSDriver wrote:
Do you mean that when you pull one/both brake levers while stationary, the noise changes and slight vibrations may occur?

Then this is absolutely normal. Pulling the brake creates a frictional connection, the noise changes and vibrations from the engine can be transmitted (differently) to the body via the brake, brake caliper, chassis, etc. When the brake is released or applied, the path of transmission of the vibrations changes / the "oscillating" mass changes.
^^^ This! On my old chopper (long front end) the feeling when stopped at a light changes dramatically when I apply the front brake or release it. With that long front fork, you get a lot of oscillation when the brake is not applied. Grab the brake and it goes from being an oscillation to a buzz like vibration. Changes the whole feel of the bike.
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