Romeo sprockets

Hi there, a smaller rear sprocket, or a bigger front sprocket either, won't give You more top speed, unless the engine has been prepared to supply more horsepower. If not the motorbike will just loose sprint at start, traction when climbing up hills, and will find it harder to reach top speed. That said, if the engine is untouched, one more tooth on the front sprocket is enough to experiment with: one front tooth = three rear teeth. Going from 13 to 15 seems a little too much IMHO.

To answer Your question, finding replacement spockets for Your Romeo should be pretty easy, with a google search I saw that it has a widespread Minarelli engine (I'm not a Minarelli expert, but my best guess is that it's a Minarelli P6 engine, given the name of the motorbike, but please don't take my word and double check that), and a rear drum that equipped plenty of motorbikes back in the '70s, a Grimeca drum perhaps. Broaden Your search by looking for Minarelli P6 front sprocket ("pignone Minarelli P6" in italian), and Grimeca rear sprocket ("corona Grimeca" in italian), You'll have to take the time to pull the "corona" and take the distance between the mounting holes (interasse), how many of them, if there are fitting poles, and if yes their size and interasse, and the thickness of the corona itself and the size of the main hole. The "passo" (the distance between teeth) is 415 for most of the italian 50 cc of the '70s, it should be marked on the rear sprocket along with the teeth number. You'll find plenty of sprockets over ebay.it, just jeep in mind that in italian it is e.g. z13 - z50, and not 13t - 50t. You can also post over the "Mercatino" area of the forum, I'm quite sure many will have sprockets for sale, just take a look over ebay.it first, to get an idea of the average sprockets price. As a side note, the chain, rear and front sprockets should be replaced at the same time: a worn out rear sprocket and chain will quickly worn out even a brand new front sprocket.

I'm not that much into the Minarelli engines, but the inside gear might be different, You should ask over the Minarelli section of the forum. Other than that the wheel(s) size has an effect too, but to be fully honest 13-51 seems a little exaggerated to me as well. Are You sure that these are the original sprockets? Before purchasing a blank sprocket make sure that Your Romeo is fitted with a plain sprocket with no mounting poles.

Usually the sprockets with that plate on top have pegs that fit into a rubber coupling inside the drum, # 10 in the picture.

Sorry but my technical vocabulary is limited, and I saw that google translate doesn't work that well with technical words! The studs are bolted (# 13) and the rubber thing is a sort of transmission's shock absorber, don't know the proper english name though. The Caballero sprockets (front and rear) cound be right, depending on the year the Caballero was built






I see. If I may ask, what do You mean by expensive regarding Your dealer's sprockets? Rear sprockets mostly sell anywhere from 15 to 35 euro here in Italy, but shipment to some countries may be expensive, not to mention custom duties. I'm not familiar with Minarelli's front sprockets pricing though. Before You waste Your money, double check that the peg size and placement matches!

My pleasure. Shipment to the UK has always been outrageously expensive, don't know what is like with custom duties after the brexit, what I do know is that now delivery takes a ridiculous time, I have heard of people needing a quick delivery having a runner taking a flight with the goods into the hand luggage in order to speed things up.

What is Your weight? 45 and a 15 front sprocket, so that if 13 - 45 doesn't work out nice You have the 15 - 45 option, wich is like 13 - 39ish. If money is no object get both 37 and 45!

Your doctor will always say that You're too heavy, and that You don't have to eat, drink, smoke, have sex and drugs and rock 'n roll, but if You're not skinny 13 - 39 will be perfect, and given that 39 it's the only available rear sprocket it's perfect indeed. Please post the outcome!