I'm new to the forum, though I've read most of it looking for some information about the Habana / Mojito 50 reparation and tuning.
I got my 2001 Habana (as they call it in Europe) / Mojito 50 last year. No restriction ring on the variator, the silencer was also tuned by the previous owner. I was riding it for a couple of months until end of August, when my silencer broke down. It just broke on one of the weldings... Investigating the cause I found that the lower mounting point bolt was gone (due to a broken thread) and the engine vibrations caused the welding to brake. Also the upper mounting point was broken. The old silencer was rusted and clogged, so I decided to buy a new one. I've bought a Tecnigas Silent Pro (the orifice is gone) as I use my moped daily commuting to work. The side effect of the silencer problem is I had to take apart the whole engine.
And that's where it starts...
Looking at the Haynes Manual I've found that I've got the Aprilia 50 cc engine, which is based on the Morini horizontal, I think one of the most popular ones, so a good starting point. The spare parts and tuning parts are easily available.
After removing the cylinder I've found that the piston rings are not doing their job, there are marks of exhaust gases all around the piston. One of the rings seems not to expand properly to the cylinder diameter while placed on the piston... Took it to the workshop, the guys told me that at least the piston and rings have to be replaced and that some treatment has to be done to the cylinder itself. I decided that it could be a good moment to invest some money in a better cylinder kit, to get some more power / acceleration.
The other thing that has to be repaired / replaced is the standard 12 mm carburetor. The mixture bolt is completely stuck, the engine runs very rich, the fuel consumption was around 5 l / 100 km (around 47 mpg!!!). It's the standard Keihin PWS carb, which I read is crap, not worth investing in. Going through this and lots of other forums I've decided to go for a 17,5 mm carb, which is a good start. And should be enough for my needs. I've found a Dellorto 17,5 mm PHVA carb for a reasonable price and I'm planning to invest in. The next decision to take is - which cylinder kit to choose?
The most important thing for me is reliability. I do not need high top speed (although up to 10 mph more would be OK), only better acceleration and more power to manage occasionally an aditionnal weight of a small 2nd person behind.
I'm not into any of the crappy chinese kits that can be bought in EU for some 25 USD, I want something that will last! And I think I prefer cast iron over aluminium I would prefer to stay with the stock crankshaft / rod / bearing, having in mind my requirements. What should I be looking at? What about the variator rollers and spring? I would say they are stock. Will they fit the setup?
Thanks in advance for your suggestions