OP
@kimpossible avatar
UTC

Addicted
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
 
Addicted
@kimpossible avatar
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
UTC quote
I know that too many miles at flat out starts to limit a scooter's top speed. And I understand this is because a groove forms. Would that also affect the speed at which the rev limiter kicks in?

After 3 days of solid interstate driving I noticed that the rev limiter was kicking in earlier and earlier. The last I noted it was kicking in at just under 75 mph. If it isn't caused by the groove, what could cause something like that.

Thanks!
@jess avatar
UTC

Petty Tyrant
0:7 And counting
Joined: UTC
Posts: 36935
Location: Bay Area, California
 
Petty Tyrant
@jess avatar
0:7 And counting
Joined: UTC
Posts: 36935
Location: Bay Area, California
UTC quote
Yes. The groove effectively alters your gearing -- only it’s not actually gears. The principal is the same, though. For the same RPM (which is what the rev limiter is based on) you will be turning the rear wheel more slowly. Thus, the rev limiter will kick in at a lower speed.
@jimc avatar
UTC

Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43408
Location: Pleasant Hill, CA
 
Moderaptor
@jimc avatar
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43408
Location: Pleasant Hill, CA
UTC quote
The rev limiter works on revs, not speed. Several things will affect the relationship between revs and speed when in top gear, especially after some long days at WOT.

The tyres gradually get a smaller diameter, so top revs mean a lower top speed.
The belt gets worn. It can't go so far out in the variator, so effectively you're in a slightly lower gear - less top speed at top revs.
The variator may get a groove - effectively reducing how far out the belt can go in the variator - see above.
The rollers (or Dr P sliders) can wear down. Rollers especially can get flat spots. This will reduce top speed as above, as the variator won't push out so far.

So they all conspire in the same direction, giving you less top speed at top revs.
OP
@kimpossible avatar
UTC

Addicted
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
 
Addicted
@kimpossible avatar
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
UTC quote
That's good. I've got a new variator, belt, and rollers to get the scooter back into commuter shape. Glad to know for sure that there isn't a separate issue to chase down.
Thanks!
@jess avatar
UTC

Petty Tyrant
0:7 And counting
Joined: UTC
Posts: 36935
Location: Bay Area, California
 
Petty Tyrant
@jess avatar
0:7 And counting
Joined: UTC
Posts: 36935
Location: Bay Area, California
UTC quote
KimPossible wrote:
That's good. I've got a new variator, belt, and rollers to get the scooter back into commuter shape. Glad to know for sure that there isn't a separate issue to chase down.
Thanks!
How much top speed have you lost?
@vintage_red_matthew avatar
UTC

MV Santa
GTS250, 1975 VBC, 1980 P200E cutdown
Joined: UTC
Posts: 4742
Location: Sedgwick, Kansas
 
MV Santa
@vintage_red_matthew avatar
GTS250, 1975 VBC, 1980 P200E cutdown
Joined: UTC
Posts: 4742
Location: Sedgwick, Kansas
UTC quote
I noticed the same thing on my GTS. The rev limiter was kicking in 3-4 mph lower than normal.

A week later the belt broke.

In my case the pulley was not groved and the rollers were not flat spotted.

It had been 9,500 miles since my last belt change. It looks like I pushed it a little too far
OP
@kimpossible avatar
UTC

Addicted
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
 
Addicted
@kimpossible avatar
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
UTC quote
jess wrote:
How much top speed have you lost?
It would only get to 67-68 on the flat. But the torque took a major dive. I know the poor scoot was overloaded, but that was in comparison to the same overloaded state.
vintage red matthew wrote:
A week later the belt broke.

In my case the pulley was not groved and the rollers were not flat spotted.
Did changing the belt fix the problem?
@max6200 avatar
UTC

Banned
2006 GTS 250
Joined: UTC
Posts: 10590
Location: KS USA
 
Banned
@max6200 avatar
2006 GTS 250
Joined: UTC
Posts: 10590
Location: KS USA
UTC quote
KimPossible wrote:
It would only get to 67-68 on the flat.
Indicated per speedometer or GPS?
OP
@kimpossible avatar
UTC

Addicted
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
 
Addicted
@kimpossible avatar
Tethys - 2012 GTS 300
Joined: UTC
Posts: 761
Location: Bowie, MD
UTC quote
Those particular numbers are GPS, as compared to 75 on the flat GPS. The before and after speed ratio is similar if I go by indicated.
@jess avatar
UTC

Petty Tyrant
0:7 And counting
Joined: UTC
Posts: 36935
Location: Bay Area, California
 
Petty Tyrant
@jess avatar
0:7 And counting
Joined: UTC
Posts: 36935
Location: Bay Area, California
UTC quote
That’s more than I would expect from the groove alone. I don’t think it warrants concern, but it may be a combination of wear factors, as Jim articulated.
@jimc avatar
UTC

Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43408
Location: Pleasant Hill, CA
 
Moderaptor
@jimc avatar
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43408
Location: Pleasant Hill, CA
UTC quote
Also, if there was extra luggage on the scooter, that would add to the drag. As the power needed to overcome drag is proportional to the cube of the speed, this also might be a factor.
@berto avatar
UTC

Molto Verboso
2006 LX150 (carbed) | 2007 GT200
Joined: UTC
Posts: 1920
Location: Toronto
 
Molto Verboso
@berto avatar
2006 LX150 (carbed) | 2007 GT200
Joined: UTC
Posts: 1920
Location: Toronto
UTC quote
jimc wrote:
Also, if there was extra luggage on the scooter, that would add to the drag. As the power needed to overcome drag is proportional to the cube of the speed, this also might be a factor.
I think drag force is proportional to the square of speed? Power would be proportional to force, so also square of speed. Or am I missing something?

(Not that it changes the point you were making)
@jimc avatar
UTC

Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43408
Location: Pleasant Hill, CA
 
Moderaptor
@jimc avatar
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43408
Location: Pleasant Hill, CA
UTC quote
Yes, the drag force is proportional to the square of the speed. Power is proportional to the force times speed. Therefore proportional to speed cubed.
@vintage_red_matthew avatar
UTC

MV Santa
GTS250, 1975 VBC, 1980 P200E cutdown
Joined: UTC
Posts: 4742
Location: Sedgwick, Kansas
 
MV Santa
@vintage_red_matthew avatar
GTS250, 1975 VBC, 1980 P200E cutdown
Joined: UTC
Posts: 4742
Location: Sedgwick, Kansas
UTC quote
KimPossible wrote:
Did changing the belt fix the problem?
Yes. YMMV.
@amateriat avatar
UTC

Ossessionato
2015 GTS 300 Super (Melody: 2015-2021, RIP), 2022 GTS SuperTech (Thelonica; bit the dust 02-22-23)
Joined: UTC
Posts: 3920
Location: Asbury Park, NJ
 
Ossessionato
@amateriat avatar
2015 GTS 300 Super (Melody: 2015-2021, RIP), 2022 GTS SuperTech (Thelonica; bit the dust 02-22-23)
Joined: UTC
Posts: 3920
Location: Asbury Park, NJ
UTC quote
vintage red matthew wrote:
I noticed the same thing on my GTS. The rev limiter was kicking in 3-4 mph lower than normal.

A week later the belt broke.

In my case the pulley was not groved and the rollers were not flat spotted.

It had been 9,500 miles since my last belt change. It looks like I pushed it a little too far
In fact, this is a good warning sign to get the belt replaced. I found this out the hard way a bunch of months back, but my belt gave up roughy 1k miles before yours did.
@waspmike avatar
UTC

Ossessionato
LXV 150 3v ie. Midnight Blue (Sold) Now Honda Zoomer X
Joined: UTC
Posts: 4109
Location: Kingdom of Lanna
 
Ossessionato
@waspmike avatar
LXV 150 3v ie. Midnight Blue (Sold) Now Honda Zoomer X
Joined: UTC
Posts: 4109
Location: Kingdom of Lanna
UTC quote
jimc wrote:
Yes, the drag force is proportional to the square of the speed. Power is proportional to the force times speed. Therefore proportional to speed cubed.
I think the horsepower is subject to the cube root. Sorry I'm not a mathematical genius.

Top speed = Aerodynamic constant x the cube root of horsepower. I think
or TS=Cx (HP ^1/3)
UTC

Hooked
vespa gts250
Joined: UTC
Posts: 246
Location: chicago
 
Hooked
vespa gts250
Joined: UTC
Posts: 246
Location: chicago
UTC quote
If it’s an older bike and it’s a very spooky feeling it might be the engine cut off switch on its way out. I had one of those go bad, they don’t go all the way bad every time, mine would randomly kick on and off while driving highway speeds, not a fun feeling
DoubleGood Design banner

Modern Vespa is the premier site for modern Vespa and Piaggio scooters. Vespa GTS300, GTS250, GTV, GT200, LX150, LXS, ET4, ET2, MP3, Fuoco, Elettrica and more.

Buy Me A Coffee
 

Shop on Amazon with Modern Vespa

Modern Vespa is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com


All Content Copyright 2005-2024 by Modern Vespa.
All Rights Reserved.


[ Time: 0.0296s ][ Queries: 3 (0.0030s) ][ Debug on ][ 313 ][ Thing One ]