Piaggio Master 500 cc - Washer and Dryer performance mod Test

Optimizing the Piaggio MASTER 500cc CVT part IV

A few weeks ago I stumbled over a post about a washy fuzzer or so... ;)

Digging deeper and finally googling "fuzzy washer" brought some more confusion.
At Modern Vespa it became a bit clearer, a guy nick named Fuzzy added a 1 mm washer to the factory installed 2 mm washer (between the driving pulley) to increase take off performance of the Piaggio Master 500 cc engine of his MP3 scooter. link, link, lotsa links

That I wanted to try for myself, hey for the price of a washer a better performance, you can´t beat that! Except with my 0 cent Mustang and Colt conversions.
Since a 1 mm washer in that dimension is very hard to find and I read about a 3 mm washer what would fit also. I wrote down the dimensions I needed and went of to the ferreterias. No big hardware store where I live.

I need a 22mm x 36mm x 3mm washer
a typical M20 washer should be: 
diameter internal 22,6 - 22,0    diameter external 37,0 - 35,8    thickness 3,6 - 2,4

The only one halfway fitting was a 20.7 x 36 x 3 mm washer I found in the last ferreteria. For 60 cent I gave that a try.

top 2 mm original washer - bottom 3 mm shiny new washer
First let´s check how important the outside diameter is

Ample space we can go up to way over 40 mm without a problem

Now let´s check how wide the washer has to be inside

21.6 mm is a absolute minimum

So we need to make the inside bigger.

A high percision and professional  Dremel knock off will be our friend there.

After reducing the grinding stick (you can tell that English is not my first language, can you?) to dust we have a fit.

Seeing that the belt had left its scratch marks inside the transmission case I decided to remove a bit material here too just to be on the safe side since I read that some people had problems with belt scraping after the washer mod.


you see where the flapping belt left it´s mark

grinding away

all nice and shiny now

To see if there is new scraping I used a permanent marker to paint the surfaces.

The indicator that the new washer is installed - the 2 mm washer nut secure locked marks do not line up.

4 days later I had to remove the washer again.
The MASTER engine was not happy with this mod.
The belt was scraping (you do not hear that) so badly that the engine died often when cold and idling. The idle was 1000 rpm cold.
There was no noticeable performance enhancement with my 6 roller Mustang conversion mod.
I hoped that I would get higher low speed rpm but it seems the contrary is the case. It does not make sense but that is a cvt for you.

Normally the Colt conversion should not work at all - but she works beautiful. Can´t really blame the folks when they don´t believe me. You have to experience it for yourself to believe I guess.

So where was it scraping?

I also noticed that the flapping belt left his marks. I had more flapping than without the 3 mm washer to my surprise.

So why was this mod a bust?
My theory is that my belt is too worn.
At around 30000 km I noticed that the engine was dying once a while when idling. I thought it was because my spark plug has reached it´s service life and in fact it got better when I installed a new spark plug.
Now I think it is because the belt stretches slightly over time since it did not got thinner in 16000 km of my Colt conversion test and I did not do any changes on the transmission.

When the belt is scraping it will remove some metal and parts of itself to fix this situation after a while.
But it puts a shear strain on the belt as the lower part of the belt gets moved in the pulleys the upper part gets permanently braked from the transmission case brackets.

If this strain gets too high, the belt begins to separate the top from the bottom layer since this is the weakest part where the anti stretch cord is between the layers.

And this is then the result:

So for now I will put the washer test on hiatus until I put a new belt in. Then I will try the 3 mm washer mod again.

... BUT since I have a new belt sitting around, I just decided when my new rollers come in a few days I will put in the new belt with the 3 mm washer to see if my theory is right and test it with the new rollers and the Colt conversion.
I will also try then to include a dryer somehow as promised in my headline ;)

Installed the new belt with the 3 mm washer and since even my old belt with the 2 mm washer already scraped on the lower metal part again (old photo) I used up 2 more of the sandpaper rollers to remove some more material. I also shot a video from the open cvt in action.

After a test ride I noticed that the new belt was smoother than the old one but did not feel noticeable improvement from the 3 mm washer in the Colt conversion.
With the extra removed material there is now a nice gap between the belt and the old "scratching post"
shot at idle speed

Maybe I will try it with a 4 mm like Fuzzy did also.


Since I did not have a 4 mm I combined the 2 and 3 mm to 5 mm and checked with the new belt.

There was instant contact from the belt to the "scratching post"

upper area the same

and in idle speed there is no improvement.

and this is when I decided to terminate the washer mod test, since 3 mm did not show improvements with the Colt or Mustang conversion. Since the 5 mm is rubbing already in idle speed the 4 mm would be a bit to close to rubbing when the new belt deteriorates for my taste.

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