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Hello everybody,
I am Nikos from Athens Greece. I just bought a 1992 Piaggio Si for my 17 year old son and i would like your help in the following. The moped is completely stock and i would like to know if i can improve the torque and the speed, with any of the cylinder kits available ( i am thinking of the DR 43 KT00066 KIT) without having to make any milling or other work on the crankcase and the crankshaft .If this is possible, what would be a good setup with maybe an exhaust, a mallossi or polini variator and possibly a carburetor without exceeding the amount of 250 euro for all modifications.
I would like to hear your suggestions on this and by the way i have to clarify that i am not looking to make this a racing bike but rather to have an adequate gain/improvement in torque and speed of less than 65km/h.
Thank you all in advance for any help
Piaggio SiHi Nikos and welcome to the site,
The DR 43 is a good option, paired with a Polini variator, a 13/13mm carburetor and possibly the Gianelli Original power exhaust,
That would make a good basic tuning ssetup for the Si and will manage to do 65km/h
Most of the cilinderkits dont need any miling or drilling of the crankcase. Only if you go higher than 43mm or want to improve performance even further thats when you start milling.
Leave the crankshaft as is. The Original piaggio crankshaft is one of the strongest out there and will do just fine on this setup.
Good luck tuning the Si and have fun!
Hello Niko’s, and welcome to this forum!
I don’t know how easy it is to find secondhand parts in Greece, but I’m sure you will be able to find something.
My personal suggestion would be to increase the size of the inlet of your carter to 12 or 13 millimetres and to use a 13 millimetre dellorto carburettor.
I would replace the cilinder by the DR evo 43mm cylinder, and replace the exhaust by a Giannelli citypower exhaust.
you should be able to find all these parts second hand, and that way you will be able to stay under €250 and increase the speed and acceleration of your sons Si. Optional you could install a Variomatic but they are quite pricy.@ SuperSi and @ Coenio111
Thank you both for your replies and suggestions. I have a question regarding the 13 millimeter dellorto carburetor, which is in order to drill the inlet of the carter, i must first remove it from the moped and then disassemble it ? otherwise the excess material will fall inside the carter ? Am i right in this assumption ?
Also when installing the DR evo 43mm cylinder kit is there anything specific that i have to do or it is just a simple replacement. Will it help if in addition to the cylinder kit, i also install a new cylinder head like POLINI Ø43mm cylinder head
Thanks againPiaggio Silook at this how to:
this is what you’ll have to do.
Yeah you’re right.
You have to take the engine out your moped, then disassemble it, then drill your inlet to 13mm(make sure to drill no deeper than 20mm , measured from the tip of your drillbit) and then you have to file it wider inside your Carter where the crankshaft opens and closes your inlet. Make sure to keep at least 1mm of ‘flesh’ on all 4 sides. There is a ‘how to’ on this forum that explains everything, that might help.also, while you have got your engine disassembled, I would put new bearrings on your crankshaft and a new seal ring in your carter and a new flywheel forelock .
you can add the 43mm cylinder head, it will improve your mopeds performance a tiny bit, but it’s not necessary. You can also drive with the original 38.2mm head.
I think Jelle might mean this how to:
You guys are great, what more to expect, this is excellent information tutorials. Do you think it is a bad idea if i try fitting the 13/13 carburetor first without drilling just to see if and how it works or it can do some damage running with less air/fuel
Regards
NikosPiaggio SiYou can do that but it won’t work.
the current size of your inlet is just not big enough to let the 13mm carb do it’s work. It will be limiting the carb so you’ll have the same results as with your 12/10 carb.Okay i understand your explanation, it is just that i want to avoid all the work for removing and disassembling the crankcase. So i will first install the DR 43 evo cylinder kit and the Giannelli exhaust and make some trials with the stock carburetor and if i am happy with it i will stay as is. Otherwise i will proceed with the 13/13 carb and all related work including bearings and seals as suggested. Thanks again everybody for all your help. If i run into problems i will come back
Piaggio SiGood luck!
Nah, you can easily run a 13mm carb without the drilling and milling.
When i bought my first moped, also a si, the 13mm carb alone made my speed go from 37 to 42.
Dont forget to jet up though!!The 43mm head will be a good choice, although the Original head can be used.
If you decide to go with the Original head you will still have to install a 43mm headgasketGood luck and keep us updated on the progress!
Thanks for the info SuperSi, i found out that my Si has a 12/12 carb on it, so for now i will stick with that to avoid further costs and as i said, if i am not happy with the results i will then buy the 13/13 carb. Also noted for the 43mm headgasket.
Piaggio Si
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