Yamaha Riva 180 Repair & maintenance information

That can happen, but doesn't HAVE to. If you install weights which are so light, that they cannot overcome the spring within the effective RPM of the engine, then you are right. In that case you would need a "softer" spring.
But let's assume that we are keeping everything else original and just reduce the weights about 10%. If at the original set-up, the sheaves are fully squeezed together at 65 kmh, now with the leighter weights this state is being reached at 70-75 kmh (?). From that point on we are traveling again at the top transmission ratio, independent of the weights, all the way up to the same(!) top speed.
Actually, you can get the very same effect of increasing acceleration RPM if you keep the same weights and just stiffen the spring.

Get ready for a completely non-fact based opinion.

I have always assumed the change of weights would change the rpm for a given speed, lighter weights would result in a higher rpm. Because power output of an engine varies depending on rpm, lighter weights might give the feeling of more power at slower speeds, so more rapid acceleration in stop and go traffic. On the other hand, if the lighter weights don't exert enough force to overcome the counter spring completely than you'll never get the variator fully closed and you'll never get the "highest" gear (lowest gear ratio) at the rear wheel. Lighter weights give peppy performance but lower top speed; heavier weighs potentially give higher top speed because you wouldn't hit a rev limiter so early, but the design of the CVT system has solid built in limits. You would have to increase the diameter of the variator or decrease the diameter of the center of the driven pulley to go faster. You could also change the gear ratio in the rear reduction gears.

If you want to read the long, long story of trying to get past the structural limits of a CVT system read the story of Craig Vetter and his Honda Helix and his attempt to create a machine that would go 70 mph, get 100 miles a gallon and bring home 4 bags of groceries. He failed.

http://craigvetter.com/pages/470MPG/Index to making the Last Vetter Fairing.html

"If you want to read the long, long story of trying to get past the structural limits of a CVT system read the story of Craig Vetter and his Honda Helix and his attempt to create a machine that would go 70 mph, get 100 miles a gallon and bring home 4 bags of groceries. He failed."

Lol...I am definitely reading this article.

Craig Vetter is definitely an interesting guy who has a lot of ideas and a very interesting history. I am not sure what to think of his scooter streamline fairings, I personally think they are somewhere between cool and ugly as hell. And while i see what he was trying to do with the streamline design, it just seems like a lot of work for little gain. But this is by far my favorite piece of the link so far.

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Propeller driven Go Kart of 1961

I am sure that some of you have thought that it might be a good idea to use a propeller to move you along. In 1961, I carved a prop for my Homelite chainsaw engine and built a go kart for it. Here's what happens:
It blows oily, stingy stuff in your eyes

It accelerates very slowly.

You don't want to do this.

Hooking it up to the rear wheels made it go a lot faster.


Craig Vetter Wikipedia:
https://en.wikipedia.org/wiki/Craig_Vetter

Again, what you are describing can of course happen, but only under certain circumstances. Such as if you are getting carried away with changing only one factor. Like only the weights.

"I have always assumed the change of weights would change the rpm for a given speed, lighter weights would result in a higher rpm."

I can not say this for every scooter, but on the Riva using lighter roller weights definitely increases the RPMs. I noticed this when I was experimenting with different roller weights, but I also noticed that you really want the RPMs at the peak in the power band. When I tried using the 5g overall weights I was getting up to around 7300 RPMs max throttle (its a cheap Tach, so its not 100% accurate), and it felt VERY sluggish, when I went to 5.5g it got the RPMs to around 7000 and it felt like it actually had some power (I haven't really paid much attention at my full throttle RPMs since installing the Dr Pulley 6g sliders since my daughter won't let me go on a ride without her anymore). I could not find a definite power band for the Riva's and what I did find showed max power output (peak Power) at roughly 6800 RPMs.

Since this thread is all about the Riva, I would like to return to that original subject.
Have you tried the trick with the horn button and the switch Illumination?
That is only one feature signaling, that Yamaha had spent quite a lot of effort to deliver the state of the art of luxury that was available at the time with this model.
One may ask themself then, why did they use drum brakes, if that was their intention, to create a hi-tec scooter?
A possible answer could be; because they thaught it was better!
Discs do have their advantages. They are self cleaning, better cooling and supposedly better to control. But since the whole of the friction is applyed at the outer circumference of a drum break, it can actually provide more breaking power.
Moreover, you may have noticed, that the rear drum is actually BIGGER than the front one. I suppose the engineers designing the Riva/Cygnus actually believed that, due to the scooter-typical weight bias towards the rear end, the rear breaks applied by a strong foot should also provide the majority ot the breaking power.
Were they really rong?

No, sorry I have not tried the horn button trick.


Motorscooterguide made a mention of the drum brakes and I tend to agree. It was common to have drum brakes back in the 80's and they probably used them because they were both cheap and easily available.

"This scooter unfortunately used drum brakes front and rear. While not uncommon at the time, at least a front disc brake is now the norm so these big Riva’s don’t offer excellent braking. The front drum does the best job it can, but performance is still lackluster." (http://www.motorscooterguide.net/Yamaha/Riva180/Riva180.html)

The European Cygnus featured a bigger tire (4.00-10) at the rear. It looks nicer and maybe contributes to a better ride. But also should be factored in when concidering the total transmission ratio. It may reduce the RPM quite signifficantly.
Have another look


Interestingly, Honda provided the Helix, that was introduced a year later, with a bigger wheel at the FRONT. Different engineers, different attitudes...

I know when I changed my tires both front and rear were 3.5x10.....it makes me wonder if they were 4.00x10 from the factory? I wouldn't be surprised at all if mine was changed to 3.5x10 cause it was in pretty bad shape when I got it.

hmmmm…..makes me wonder why they did 4.00x10 in the rear on European models when American models were 3.5x10 front & rear?

Maybe for that very reason, to reduce RPM, noise and emmissions in the simplest way.

Edit: and while we are at it, why did they call your Cygnus (Latin for swan) Riva (beach)?

Maybe. I also wonder if it was a different model thing.......Yours seems to be a deluxe model, while most were just the standard like mine. There isn't much difference between the models that I can find, looks like the Deluxe model mostly had cosmetic differences like different seat and a factory installed aftermarket windshield (both of which yours seems to have). Makes me wonder is all deluxe models came with 4.00x10 rear tires? Or as you stated....it could be just to reduce noise and emissions. I know mine had 3.5x10 tires in both front and rear, and the motorscooterguide website shows the tire size as 3.5x10 front/rear but they don't get into much differences between models.

The early Honda 250 Elites had a little green light under the bars that lit up the key area when the horn button was pushed with the key in the off position or not in place. I had mine for years until I accidently discovered it.

Damn.....now I am going to have to push the horn button on every scooter I come across.

As much as I am informed, the Cygnus for the european Market hasn't had different specification levels. The version that you see was the only one available, and also only in this color. It doesn't have the king and queen seat nor the floor carpets of the top specification model for the US market.
I also received a wind screen with it, an after market screen if I know correct. the bracketts for it are still installed on the mirrors, but I never tried it on. I prefer the laminar streaming of air around my head over the turbulences behind a screen. But something tells me that the screen my just help gain a kouple of kmh top speed.
Any experiences with this, please?

I have not tried it with a Riva, but the Honda Elite 80 I used to have definitely got a few more mph in top speed from having the windshield and I would imagine it would be the same for the Riva/Cygnus. It was nothing major, with a windshield it would get up to 45 mph (top speed) and without it around 42 mph. I would assume it would be a slightly bigger difference on a Riva/Cygnus, because that was a 80cc scooter but I am just assuming

The marketing decisions made by Yamaha and Honda in the '80s were strange, with different names for different countries and different mechanical specs. Honda put disc front brakes on the Elite 250 in Japan and Australia, maybe in Europe, but not in the US. Car companies still put different names on the same cars in different markets.

That little light over the ignition switch is kind of nice to have in the dark, but most people never knew it existed. Now I just use my cellphone flashlight.

I'm not a windshield user, so I can't say this for sure, but to me windshields feel like they upset the handing of the scooter, with a big effect in windy conditions. And at speed it feels like the scooter is pushing hard through the air. With a full face helmet I'm happy with no windshield at all.

I haven't checked this thread in a long time, and have never owned a Riva, but I am a firm believer in repair rather than replacement. I was just wondering how hard it is to find parts for these scooters?

Compared to other scooters, not really too bad. Ebay has a lot of the general parts for them. The big problem that was killing these Riva scooters off was there was no replacement drive belt and every website out there said that the rollers were special and you would have to custom make them. But we have overcome both of those problems with finding a gates replacement belt and figuring out the rollers are 17x12 which is not a common size, but also not impossible to find either. The Rivas are pretty fast and generally compared to 250cc scooters instead of the 150cc's and I tend to see them sell for pretty cheap. In fact, I was looking today and saw one with 6500 miles on it selling for $550 on craigslist, post said it only need fuel lines replaced (but almost guaranteed it also needs rollers, they always do). In perfect condition they tend to go for between $1500 and $2500 here in Norcal.