70CC 2004 ZIP NOT RUNNING RIGHT!!!

This build has been going on for 8 months due to time and money, it's a joke and i'm at the point of chucking it in a skip.

70cc cast iron malossi kit
17.5mm carb with 65 jet
stage 6 pro exhaust
polini open airfilter

Sometimes starts and revs okay then cuts out
sometimes it wont start at all
sometimes it'll idle and rev up often but then will cut out on throttle after like 20 seconds

Someone please just tell me what to do.

 

Start with a bigger jet and air box. Sounds too lean. A 70cc kit needs the high volume of air but you need more fuel. The open air filter will run lean and be difficult to tune correctly so if you are keeping it on I suggest getting a pack of jets from 80 to 110 and try large first. Trial and error. If you can then put the air box back on, tune the carb then when its good you might consider trying the open filer with even larger jets.
Find out what your stock main jet would be, increase 10% for exhaust, increase 25% for the 70cc kit and you'll be just about in the ballpark with the jet size. Open air filter then increases even more.

 

Its sounds like the jet is to small, because you are running a 70 kit on it and only using a 17.5 carb the float bowl is to small and isnt holding enough fuel and your basically running the float bowl (carb) dry, its not producing a sufficient fuel flow to the engine, you will need to up your pilot jet and main jet or just do the easy option and buy a 19mm carb and run and high jet, i run 110 jet on a motorforce 70 kit, i used to run my 50cc with just an airfilter and exhaust on a 65 jet, so your jet is deffo to small