Piaggio Master 500cc - 1 Year / 16000 km (10000 miles) with the 4 roller Colt conversion

the truth about my crazy experiment I

I started my Colt conversion experiment 2009.8.10 with 19.000 km, now 2010.8.22 one Year and at nearly 35.000 km so 16.000 km (10.000 miles) later it is time to see how it worked out.

If you are new to my blog, here a short recap for you.

I wanted to replace my rollers with the Dr Pulley sliders but on my way to find out if I had a 6 or 8 roller setup I had to take the variator apart. Since in the discussion groups there was always mentioned a lower weight for better acceleration I wondered what would happen if I would remove 2 rollers from my 8 roller setup. I was so amazed from the performance boost, that I wanted to know what happen if I would remove 4 rollers. Then I got into measuring and testing the 8, 6 and 4 roller setups for acceleration, RPMs and millage.

What the 6 or 4 roller conversions are doing, is moving you in a more optimum power band. Pretty much the same as all the other mods what change things at variator level.

You find the details in my older posts.

During the 16.000 km I swapped the rollers after 10.000 km with the other original 4 rollers because the plastic started to deform a bit and started to look like Dr Pulleys on drugs. The stainless steel insert did not deform in any way so the plastic was just moved into a more convenient shape. That this could happen was my fault, since I had to remove the stabilising side of the plastic when I was testing the Woody conversion and wanted to get the metal roller out of the plastic hull.

The performance or riding experience was not different, I just changes them to be on the safe side.
Now we are talking about still the original stock rollers what came with the 460cc Piaggio MASTER engine and were working 19.000 km as a 8 roller - and 10.000 km as a 4 roller setup.

After 15000 km the millage is still pretty much the same as before. I still have sometimes the slight vibrations  in the 5500 to 6500 rpm band but they are no bother at all and nothing vibrated loose or had any other effect.

I switched to synthetic oil but will switch back to normal at the next oil change.

The whooooaaaahh feeling is still with me every time I ride and watch the rpm jump from slow cruising to 7000 in an instant when I open the throttle. And this is exactly wher you want to have your RPM at the MASTER 500 because this is the max torque with max HP point.

The stragled sealion what was gone completely has come back faintly after I passed the 30000 km mark when I ride the low speed twisties in the mountains and the clutch has to reengage while hot. BUT is in no way remotely as bad as it was with the stock engine.

During the 16.000 km I tried several times to improve the colt conversion, with some 8 roller woody / steel combination. Even with the same weight this did let the engine spin much to high and with 95 gram double steel it did not work either.

In the next weeks I will look for a heavy duty plastic and will try to find out what the best 8 roller weight will be to have the same performance as my Colt conversion.
When I have that exact weight I will either find a way to make them myself or will talk to the guys at Dr. Pulley and see if they are interested in making this max performance rollers/sliders.

So for the final conclusion, did the Colt conversion was a 100% success?
Short answer is yes - without any reservations.

So to put the result in one spiffy sentence:

The Colt conversion it the ZERO money mod what brings you 30% better acceleration, eliminates the paint shaker and the strangled sealion, makes your bike feel like it has a sports bike engine, installs a fat grin on your face every time you open the throttle fast, has no ill effect on your gas bill, transmission belt or engine, gives you the extra edge in passing cars and you can do it yourself right now.

Come on, where there really no snags or drawbacks at all?

Well, come to think about it, my wife complained about that her right foot got too warm.

Now you need to understand, where I live is the whole Year between 20 and 30 degrees warm, so flipflops or open shoes are very common for us on the bike. And since Malaguti put the pillion footrest just above the unprotected exhaust pipe before it enters the muffler the combination of higher RPM, waiting on a red light and unprotected feet made it necessary to install a heat shield between the muffler pipe and the footrest.
Problem solved.

... and I like to mention you really have to watch your speedometer because in the beginning you will be over the speed limit quite often...

...and yes your gas consumption might rise a bit because it is just too much fun to rip open the throttle again and again but mine never rose more than 5%...

Folks who did the Colt conversion


Completed Joe's Colt Mod. Very, very happy. Have not had opportunity to measure the difference, but it is significant by subjective measures. Here's my initial, highly subjective take on it. Bear in mind that I replaced belt & (4) rollers at the same time, so part of the perceived difference may be attributable to the new belt & rollers.

At least a full second off of 0-60mph
Accelerating uphill radically better
Acceleration response to WOT above 50mph better
WOT from full stop brings the tach up to 7k+ very quickly, and then smoothly back down to 4-5 if on the flat under 50mph
Noise, vibration, smoothness all comparable to 8-roller setup, given the understandable pitch change for higher revs. I would say even smoother in the 3-5k band.
Acceleration drops off more abruptly upon releasing throttle
Upon coasting to full stop, a steeper and slightly delayed drop down to idle RPMs.

In short, still a very smooth machine with noticeably more punch on the acceleration. This mod is dangerously fun on twisty-hilly road.

Thank you again Joe for trail-blazing!!



  1. i have 125cc scooter. it's a kymco and its variator only has 6 rollers, can i use only three rollers? have you tried your method in a low cc scooter like 125cc? kindly please reply to me at: paul@teknixcap.com

    many thanks

  2. Nope, only with the 500cc. In your case I would remove 2 to see how it works out. - If you do, let me know.


If you want to talk to me, use the comments box at the end of the post. No need to register or log in. If you use a name it is easier to answer to you.