Hi, I have a Malaguti Yesterday 50cc which has the 50cc Minarelli engine that most of the big make scooters have. When I got it, it had a 76 main jet in the standard 12mm carb. The scooter was bought as a project to do up and keep. It’s a retro looking bike and that’s how I would like it to remain. The original exhaust was shot so I bought an aftermarket exhaust that looked the same as the original to keep it looking standard. I have changed the main jet to an 80, took out the rubber reducer from the airbox, changed the filter to a Malossi red foam one and put an unrestricted CDI unit in it. I’ve done some tuning and the scooter is running fine, no stutters and pulls throughout the rev range. The problem is the 43mph (says on speedo) top speed. I’m looking to get about 55mph out of it so I can keep up with traffic on a 50mph dual carriage way I use frequently. I’ve done some research and I was thinking of a 17.5mm carb and a Polini 70cc big bore kit. To start with I’m just going to try changing the carb and see what top speed I get. My question is if I’m going from a 12mm carb with a 80 jet what should I start with on a 17.5mm carb? Ive seen carbs selling with anything from 75 to 98. Is there a general rule of thumb when upgrading carbs only? I don’t want to change the exhaust or airbox, worst case I could add some more holes to the airbox where they cant be seen to get more air in. Thanks
have a look on pedparts blogs about the polini/malossi big bore kits.they used a few different carbs and gave a few jets a run through too.polini and a 19/21mm would be a good set up and you wont be disappointed.standard exhaust might restrict the final top end but your get easy 50mph once its set up.standard carbs are restrictive.
HI Thanks for reply. ill have a look tonight. Im in the process of taking the old carb off. Its a Gurtner PY and ive found a hose that looks like its not meant to come off. It runs to behind the fan. Any idea what it is and can I cut it off and attach it to the nipple of the new carb?
that pipe is meant to be like that.you could make it longer and tuck it away..cant remember if its a breather or over flow but its extendable.
Cheers for the help hairyjim. Just found out ill need a new throttle cable as fittings are different and the seal on the auto choke unit is shot.
well it sounds like you need a call to peds are us or some where and get a new one.be surprised what a good carb can do.quality17.5 and set up right your love it.
