I have a piaggio zip 2t ac with a malossi 70s, 17.5 carb with a 65 jet, malossi variator, malossi belt, a yasuni exhaust and a stage 6 foem air filter, it runs alright at 3/4 throttle but bogs at full throttle do I need a bigger jet? If so which correct jet should I get?
I would say a lot bigger jet. While i cannot tell you what jet size you need, as every engine is different, its just a case of trial and error. But what i can tell you is i have a Piaggio NRG (so basically the same engine) with a standard cylinder kit, Polini HI-speed variator/clutch kit, Tecnigas Q-tre exhaust and im running a main jet in the 80's! Start with a bigger jet than you think you will need and work your way down, following the many carb tuning guides that can be found all over the internet. Thats all i did. I would hazard a guess that you could be needing a main jet around the 100 mark. Someone else more knowledgeable than me will likely be along soon that can give you some better advice than i can mate.
65 jet is to lean , please do not be running hard like this , it will ruin your top end quick try around the 90 mark get a set of jets from about 78 0 90 in 2 size increments ie 78 -80 -82 -84 start with the largest first, if its to rich its gonna run like a bag of shit, infact may not even tick over-start then you drop down by a size jet ( 2 sizes for you ) on every test until you find the area where its kinda just sweet. you should do a hard run flat out for a couple mins then chop the ingintion off when max out on throttle, coast to a stop with the motor off. remove plug and check the colouring , we chop the ignition off when flat out to preserve the state of burn at that very time . colouring of plug tip area: white - off white creame = to lean need to go up in jet size cabon sooty black = to rich need to come down a size in jet chocolate brown = perfect not to lean , not to rich its just right , aim for this colour all the time
Cheers mate I'll take note, but what if I got a 21m carb with this same setup, then what jet should I run?
21's usually come with larger jet pre installed , my old 17.5mm came with a 90 jet installed . try find out what jet is in it, its a good chance your going to be down jetting slightly
I have just fitted a 21mm universal carb, atm it has a 90 jet in but it is running horrible bugging of 1/4 throttle, I think it's either getting the mixture screw and idle screw correct so it's air and fuel balance is good or it's just that I need a bigger jet, I have got a 102 jet, it screws in but not tight, It is a open air filter which is installed btw.
