Modern Vespa

Vespa px125 with DR177 and sip road 2.0. It's a 2003 UK MY model with the soft pull clutch. On gps I hit 64mph but it's screaming it's tits off. Acceleration to 50 is very rapid and it's pretty good getting to 60mph. So around local roads it's great for overtakes but on dual carriageways where traffic going 60mph it's an uncomfortable drive as you feeling like you're going to blow up due to high revs and lack of higher gearing. Appreciating the compromise of changing clutch cog between acceleration and top speed , shall I go 21 or 22 cog? 22 cog will be 10% upgear . My aim is to be travel at 60mph without the screaming engine . Can I also ask whether 21 and/or 22 cog will fit from a 20. What's your experience of changing cogs? Too high gearing so can't pull anymore , problems with wind, hills. I'm going to stick a road 3.0 pipe on too. Thanks all

At some point the DR kit will give out. The old technology copes very badly with wear and higher rpm.
If stock you have a 68 helical ring gear. I would fit a DRT 40mm 23 tooth. It will be fine for now and a modern kit and a molle clutch can also use the same cog later on.

But does a DR have enough power to drive a 23 cog? That's a 15 percent upgear ? Thanks

My Stella has a 22t clutch cog and I'm running a Polini 177 with a 60mm crank. 60 feels pretty reasonable. Definitely not screaming.

I just went to the 22 tooth on my '05 Stella for that exact reason, it was unnerving the way it was screaming at highway speeds. It still pulls great, but cruises at 55-60 MPH at 6000 or so RPM's. Big improvement over the 21. Mine has the Pinasco AU kit.

P150X
DR177 with Malossi head
Mazzucchelli racing(? ) crankshaft
24/24 drilled to 2.5mm
SR2/Polini Box
Sip touren flywheel

22/68 was really nice
23/68 was nice before you need shift from 3 to 4. I need to rev 3 really high to scream to get proper dynamic on 4th.

With the 22t, 4th is very usable and not a big jump from 3rd, like on the 200. It feels pretty well matched to the power band and never like it's lugging. I can imagine that 20t really would be screaming and the 21t, not much better.

Mine uses a 23T clutch cog + the 68T primary. It's brilliant and I'm 75kg for reference. PX150 2012 + Jasil 57mm crank + DR177 + VMC zero squish head + 1.0mm base packer + 24/24e + BB Touring. I love this setup so much I've left a BGM 177 kit on the shelf and also have the option of a stock PX200 engine for this scooter. When something works this well, I don't want to mess with it.

That's good to know. I might give the 23t a try in a spare clutch at some point. Easy enough to switch back. I live in a mountainous area and worry that that I would end up lugging a lot on hills, but it's worth checking out. I have yet to try one of the newer kits and might be a bit partial to old school cast iron.

Thanks for all the replies . I'm just after a simple change and I think the 22 cog is best option for my setup. I appreciate I can hit 64.5 mph gps as is but just want to be able to comfortably go 60 mph to work and back. Most of the time my px used to potter around local where speed limit is 30/40 . I have a 24mm carb and Im hitting 60 mph gps with 3/4 throttle . The road 2.0 kicks in at 55mph and it's hard to keep the speed back. It's here it's in it's power band and just wants to pull and pull so that 22 cog will tame the revs down. What make do
You recommend? I'm looking at a BGM which is about 50 quid.

Just bear in mind that mine is somewhat tuned, not a bolt-on DR177. I think you'll struggle with a 23T clutch in a hilly area, unless you've gone the extra mile. By that I mean cases and cylinder ported/matched, cylinder lifted to raise the transfers, squish reduced, inlet lengthened. All easy to do.

Sorry for the assumption that DR kits are always slapped on. Just because they're old tech, doesn't mean they're not worth the trouble of going the extra mile.

My engine has tame timings, big squish, not matched, so the 22t seems about right unless I revisit all of this at some point.

Nailed. Exactly what I got when try my bolt-on DR177 with 23/68 primary. Then I went back to the 22T. It also seems that short 4th gear is the solution in my case.

Long primary, 2+ tooth shorter 4th