Modern Vespa

Kit is the usual DR177. This is actually a pretty good kit. The piston is the weak point. It uses thicker piston rings and these can't take high rpm without snapping and making a mess. If the cylinder is adjusted to keep the rpm under 7500, it will be very reliable.

On a 57mm crank if you set the TDC to be 1.50mm short of the top of the cylinder the port timing will be good. The challenge for you will be to get the squish to 1.00mm. Going to need to either shorten the cylinder or get the head turned down to slip inside the cylinder.

I recently got an MMW head turned to slip inside a 200 cylinder and the guy in the machine shop only wanted £30. I gave him £40 but I was expecting £50, so everyones a winner. This is the easiest option for sure.

You might need to grind the exhaust port but leave that until you have run it in, as it might be ok. It has the 3 exhaust ports and these really help with additional blowdown capacity.

Thank you very much. I'll see what I can do with it. I'm having difficulty finding a GS piston though.

https://www.sip-scootershop.com/en/products/piston+grandsport+177+cc+_12037000

If you are putting the Pinasco on in the Winter, the original DR piston will do until then.

What gearing options you have? Any spare clutch cogs? Can't be doing those kind of revs at 70mph on a DR177.

Hello Jack.
Thank you for your advice. I want to be able to maintain what my scooter can do on a good day, no more.

I started to tune the engine a bit when I had the chance in December when it was in bits. Given the time I would have done the whole job on it. I have ridden over 1500 Miles since the quick rebuild.

What I love: I can overtake Lorries just about. It always starts second or third kick and runs until I'm finished. (Apart from the odd Gremlin).

What I hate: I can overtake Lorries. I try to cruise at 60 MPH but given the level of the Terrain, I hit 65 and a couple of Miles later I'm doing 55 and the Furious Lorry drivers overtake again.

Thanks for the link to the Piston. I paid £150 for the Kit. Is it worth throwing another £100 in the Hat?

As this is to be a temporary change I would just run the original piston. If you can keep it under 7500rpm it will stay in one piece. I guess you have a 20/68 primary. If this was 21/68 or 22/68 it will keep the rpm lower. You'll need higher gearing for the Pinasco anyway, so this money won't be wasted.