Silver Wing Shifting into Overdrive

I have a 2003 Silver Wing 600.  When I excellerate to around 55 to 60 mph my Wing shifts down dropping RPMS down about 400rpms.  It actually does this twice dropping about 800 RPMS totally.  Like having 2 over drives in the transmission system.  It cruises nicely at about 4900 RPMS at 60 mph.  I have asked a couple of dealers about this and they don't know what I'm talking about, not surprising.  Does anyone know how this works and where?  In the CVT? The clutch?
The previous owner put in 26gm Dr Pully sliders too.

Sorry, I can't quite wrap my head around what you're experiencing. However it's late in the evening and I've spent the day riding in 90+°. So my brain is pretty fried.

Here's a link to a CVT explainer from the Modern Vespa forum. Vespa CVTs are slightly different than our Silverwing CVT transmission in that the clutch bell and clutch shoes are on the "inside" rather than outside but the basics are the same. Hope this helps your understanding. 

http://modernvespa.com/forum/wiki-cvt-principles-how-it-works-how-to-improve-it-

Tim

There are no shift points, CVT drive, headed out for a ride this morning just might play with throttle position and note speed vs RPM. How many miles on your S'Wing?

Good Morning Dibber. I haven't paid much attention to the "shifting" on my 08 SWing. I also have 26 gram sliders in mine. About the only thing I've noticed with mine is that when taking off the rpms get up to around 4,000 sort of quickly then slowly climb as I accelerate more and the speed goes up. But I haven't noticed any drop in rpms like kicking into overdrive.

If what you are saying is it that the RPMs increase as you rapidly accelerate then once you've achieved that desired speed and begin cruising the RPMS seem to drop, then that would seem pretty consistent with the way Dr Pulley sliders function. Though an 800 rpm drop seems to be a lot. As far as "shifting" two times, ya got me.

Dr pulley sliding weights do act differently than roller weights

Tim

My Wing has a little over 4000 miles. The previous owner replaced the tires, belt (because of age), and added the Dr Pully sliders at 2700 miles. I haven't pulled the CVT to see what it looks like. Will do soon.

I have a Vespa GTS300 Super and had a Buddy125. I do most of my work, but never had experience this action before so I asked the Wing pro's and thank you for your help. I thought it had to do with the CVT.
Dibber

I just returned from a ride, steady throttle level road the only time RPM would go over the Speed / RPM norm is when I throttled up hard, same for a long uphill haul.

There's no designed in "overdrive" shifts in the CVT system. It sounds to me that there's something preventing the belt or rollers from moving smoothly in and out.
I would suspect there's some wear or belt material on the pulley faces or a problem with worn rollers. The normal operation of the CVT is a smooth change in ratio with power changes. Any friction in the system could cause a belt to stick at one ratio and not change until the power was increased enough to overcome the resistance.
It would be worth looking at the CVT to check the belt, clean up the pulley faces and remove the black dust from the belt. Possibly the belt is in need of changing.

exavid wrote:

< Snip >The normal operation of the CVT is a smooth change in ratio with power changes. Any friction in the system could cause a belt to stick at one ratio and not change until the power was increased enough to overcome the resistance. < Snip >

 Hmm... Could it be that the Guides & Pins on the moveable face of the Driven Pulley are binding? Given the lack of use vs age it might warrant stripping the Driven Pulley to regrease those pins, etc and insure that the moveable face is operating smoothly. Could be that that old grease has dried and caked up.

Two videos of the legendary Stephano Bonacasa refurbishing the Driven Pulley:

https://m.youtube.com/watch?v=szWjD9fDUy8

https://m.youtube.com/watch?v=82MUIwzfCPo

Well it has been raining all day so far, which we need. So I put on Wild Hogs in my DVDs player and opened up the CVT. Man was it dirty. Some of the ramps had a lot of belt dust caked on them. So I cleaned everything up put a little of Gunk silicone spray on the slider ramps and it made a big difference. The Wing is running very smoothly. Problem is solved and a new lesson learned.
Thanks again for all your replies and support.
Dibber

Glad to hear you got it straightened out. We can't have people think SW CVTs are anything but silky smooth.

I notice a bit of hesitation when I roll on the throttle. My 2007 was stored in a heated basement for some years before the owner decided to part with it. I am going to take the driven pulley assembly apart as soon as I have the parts in hand to do a basic clean-up and re-grease etc that it probably needs. I did not see anything more alarming than belt slap marks inside the cover and some black powder by the bearing in the outer case.
But after reading Dimond's posts in another thread I figure it's best to play safe and take things apart and do some basic maintenance.

Jay.