Modern Vespa

I've done belt and roller changes several times without issues, but this time something doesn't seem quite right.

I'm doing final prep for Cannonball and was due for new belt and rollers (they had been in for about 9K miles). I was hitting the rev limiter at 74 MPH per GPS, but I've confirmed 80-82 on my GPS previously and regularly.

My rollers had significant flat spots when they were removed. The old belt still looked in good nick, but was .02" narrower than my new one (measured with my calipers) and was replaced.

New rollers are 12.5 gram Malossi rollers (same as what I took out) and the new belt is also Malossi. I did replace the half pulley with a new Malossi part as the old one had 2 broken cooling fins. I already have a Malossi Variator and didn't need replacing - just a good clean-up.

Buttoned all back up, all nuts torqued to correct specs, and went for a longish 270 mile ride. Now the bike has a hard time eclipsing 70 MPH on the flat roads where I was previously hitting 74 and the tach shows under 9K RPM. I did manage to hit 77 MPH on a long steep downhill, but still never hit the rev limiter. Prior to the service, it would hit rev limiter on this same downhill and just barely hit 75 mph. I'm also running a 140/70-12 Pirelli Angel rear tire, not sure if that would affect hitting the rev limiter.

Any help is appreciated.

Hmm, perhaps you should sit this Cannonball out until problem resolved as you know I will be passing you!

But to be serious, not sure what the issue is, are all the guides clean, no weird markings, etc? Maybe replace the entire variator? Looks like some had more wear than others so out of balance if that is possible?

If it were me, I would take it apart and inspect everything. It *could* be the wrong belt, but that seems unlikely. It could be the new rollers sticking in the slots -- they should move freely but not too freely. I have occasionally had to sand one edge lightly to get them to move.

are you 100% sure it's the right belt?

the original GTS belt and the HPE belt are slightly different ... think it's about 7mm different in length.

Edit: Just noticed that you ride a 250, but the same point of double and triple check the belt part number applies

Agreed. This is definitely something to check.

Malossi has one belt that fits all the GTS and GTV Quasar engines, including the HPE. If you got it from someone who's not trying to sabotage other Cannonball participants, you should be fine.
Are you sure the rollers are 12.5 grams? The Malossi variator comes with 14 and 16, probably 14 and 15 when you bought yours. The 250 has a very low factory rev limiter, and lighter weights would definitely make you bounce off it sooner than before.
If it's pretty much what you put in before, definitely take it apart and go through it again. Something's amiss. And if you did other work at the same time, is there anything else that could cause it to slow down? How is your tire pressure?

So...I had ordered 2 belts (part no.6113027) and two sets of rollers (part no. 6611095 20x17 12.5 shown on the label and the rollers themselves). I think the stock OEM roller weights were 11.0 grams, but perhaps that's not applicable with the Malossi Variator. I did place each of the rollers in with the edge print facing counter-clockwise, but not sure that would make a difference.

I reused the orange variator guides as the green Piaggio ones I ordered won't work with the Malossi backing plate, and they seemed to be in good shape. Tire pressures are 26 front and 29 rear.

I opened it up again re-seated the belt as far into the clutch as I could, checked the movement of the rollers and they seemed OK. Confirmed reassembly order of the washers and retorqued everything.

Still same result, so I am a bit baffled.

The Malossi variator guides should be black, not orange.

I bought what is pictured below, and it came with orange guides. I do have a set of black ones as well, perhaps I should swap them out?