Next Vespa Bravo upgrade, a Polini Speed Engine. A very nice engine case with enlarged intake and bored to accept 46 mm cylinder kits. Nothing you can’t achieve on a stock engine case, but i got it for a good price from my friend Nikolaj.
I bought a special intake manifold from Italy, made for a 15-16 mm SHA instead of the normal Piaggio SHA 13 mm carburetor.
I mounted the engine with a used original crankshaft, new bearings and seals. The intake opens 130° before TDC and closes again 51° after TDC, giving me a total duration of 181°. Good for many of the cylinders that are out there. I’m not sure what cylinder i will use, maybe a Polini 46 mm. After all, it’s made for this engine case.
Stay tuned for future updates!
The Bravo is finished, drives very well. Comfortable, quiet and a bit slow 😉
A short video right after my first ride.
And more pictures:
A local guy brought me this engine, he bought it restored many years ago, but didn’t use it much. The changing temperature differences gave condensation in the engine case and caused a lot of rust damage. The oil was brown and very thick like mayonnaise.
I changed the damaged parts, did some machine work to worn bushings and rebuild the engine with new bearings and seals.
I thought i didn’t need more mopeds for now, but then a old friend messaged me. He had this Vespa Bravo that he couldn’t get done. Everything was disassembled, engine and everything. The price was ok and included delivery, so i felt it was my duty to save this (once) fine Moped.
My first plan was to assemble everything as is, but the paintjob is just terrible . Everything is sprayed over, it needs a new paintjob.
The engine got a quick cleanup, new bearings and seals. The crankshaft was a bit abused, i’m giving it a chance. I’m running a original cylinder, the inlet timing and restriction are modified a bit. Just enough to pull a grown man, no racing engine… yet!
More information is found in the image descriptions, i will update the galleries with additional pictures when i get more work done.
To get better acceleration on my Puch Maxi, I adjusted my clutch to engage later at a higher engine speed. There isn’t much bottom end in the Airsal kit, with a heavy gear ratio it needs to build up some RPM before take-off.
I started with some stiffer springs, with as much preload as possible. Then i took about 12 gram weight of every clutch shoe. I ended up taking it down to 73 gram before i was happy with the result. I wouldn’t mind making them even lighter. Remeber to get an even weight and spring adjustment on all shoes.
I haven’t used my Puch Maxi in a long time, the aftermarket wire rims and cheap tires had a bit of vibration and the engine lacked power. I bought some Grimeca cast wheels and nice Schwalbe tires. For the tuning i got a new engine from my friend and club member Esben, don’t want to race the original number match engine.
I rebuild the spare engine with new bearings, seals and a stuffed DMP crankshaft. The topend is a 45 mm Airsal 4 port cylinder with a DMP head, the head isn’t designed correctly, i will need to make some adjusting. I started with a 15 mm Bing replica, but liked the 12 mm original square Bing more. The exhaust is a Jamarcol straight pipe, doesn’t make much noise and has pretty good performance. I need to adjust the clutch with lighter shoes and stiffer springs, there is not much bottom end in this Airsal kit.
More pictures and comments in the gallery below:
I’ve made scans of the Gilera 50 engine gaskets, for the engine cases and clutchcover. You can download them here in PDF format (click the links below).
You need to print them without any scaling, 1:1 / 100%. The engine case gasket is too large for A4 paper, you need A3. You can print on gasket paper and cut it yourself.