Modern Vespa

Hi there.

I recently replaced the front fork seals on one tube of my front forks because it was leaking oil pretty terribly. I have the factory manual downloaded for the 2007-2012 Piaggio Fly 150, and originally ordered the oil and dust seal in accordance with the specs in the manual.

HOWEVER, when they arrived they didn't fit. After doing research, I discovered Piaggio used a slightly different fork tube on the 2006 year version specifically. After getting the right seals, I was able to complete the seal replacement, and they no longer leak oil !

PROBLEM: I used the 2007-2012 manual which states, and I quote, "30cc (+/- 1cc) 20W fork oil" for the forks (see actual image from manual, it's a pretty terrible service manual IMO)

I used a graduated syringe to add the stated amount and put it all back together, but the suspension is WAY too squishy and bottoms out just coming to a normal stop.

So, obviously I need to add MORE oil (because it isn't going 'on block' and compresses easily), but I now have no clue HOW MUCH more... and of course I did the dumb(smart?) thing and also changed the oil in the GOOD tube with fresh oil to clean out all the gunk and make sure they had the same weight oil and volume, so I don't have anything to reference anymore.

Does 30ml (30cc) sound wildly incorrect to you all? How much should I try next? How do I know if/when I add TOO much?

What was the OEM code of the correct seals??

And a photo of the fork would help cause they had 3 different forks during production (Escorts, MVP, Wuxi Top)...

30cc is only an ounce. When I do the fork oil in my 50cc Yamaha it takes 45cc/per . I use a Nyquil cup. I would guess that 30cc is not near enough for your 150.
This might help at 5:40

Good seal was part # 599201 (31.8x42x7)mm, pictures attatched. I dont have a ruler/calipers on hand where I'm at right now, but standard size card for reference on travel distance (about 4/5 of the card length is shiny = 2.7 in = somewhere in the ballpark of 68-72mm travel?)

EDIT: Also the 2007 Manual does mention the Wuxi forks, so perhaps mine are one of the other two types?

(Ignore the oil streaks on wheel lol, I cleaned the front brakes when I did it)

OK. Fork was made by MVP. Unfortunately, as you have already figured, there's no updated info from Piaggio. Last fork they installed on the "old" Fly and still used on the newer model was made by "Wuxi Top" and manual said 96cc of 10W fork oil...

While the tube is fully compressed, is the valve in the bottom fully covered by the oil??

What I always do when replacing seals is to keep the old oil in a cap so I can have a "guide" for the new oil going in...

Unfortunately, now it's just trial and error. I'd up it to 50cc and test...

Yeah, Unfortunately I was a bit lazy after already having wasted my time the first time I took all the damn plastic off to be able to reach the retaining ring on top of the tubes to pull them out, didn't feel like getting any of my indoor glassware dirty and didn't have anything disposable on hand except a big old oil pan.

I will try 50ml and see how it feels. I'll be happy as long as it isn't bottoming out, don't really need it that stiff (maybe 20W oil was too thick?), maybe find a local speed bump and take it at a slow speed until it can handle it?

You should be happy Piaggio used the same brand of fork on both sides of the scooter.

The MVP front forks were pretty common on the Gilera Runner. Maybe one of our European friends can tell you how much oil they take that way.

Runners had Sebac, Escorts and Kayaba forks. They took 125cc of 7.5W oil in each leg...

*Ahem* well, I wasnt going to mention this, but the internals for each fork were a bit different... one side had a guide rod with 2 holes in the bottom and a slightly different looking piston-thingy... so yeah...