Get the main jet right, then knit pick the rest of the fuel delivery. The other major part of carb tuning is the pilot jet. In basic terms the pilot jet is responsible for maintaining a constant level of fuel to the engine while its running. At idle for instance when the needle is either all or almost all the way in, and not allowing the main jet to supply fuel to the engine — it still needs fuel.
This is where the pilot jet kicks in. In most cases, the factory pilot jet can be left alone. The pilot jet also acts as a sort of reserve of fuel for the engine to have ready for when throttle is rapidly opened.
This is because there is a short delay in supply when lots of fuel is suddenly required from the main jet, as it needs to travel up the fuel feed, past the needle, ect.. Panicking and changing 5 things to try to fix a tuning issue often leaves you worse off than you were originally, and you have no idea what change did what.
Maybe one of the changes was right, but the other four changes were wrong and hid the benefit made by the right one? Tuning is alot of trial and error.
Changing one part at a time is the only way to distinguish error from correction. As stated above, the main jet is the most important tuning aspect to get correct. If the main is too lean, you run the risk of seizing the piston. If its too rich, the plug will foul and the bike will make alot of smoke and not go far. Theres a reason for this huge difference in jet, you guessed it too — its carb size.
Bigger carbs require a smaller jet, as a general rule. This is normal. For this reason, the best port of call generally is to start with the standard jet included in the Malossi Carb kit. Its often pretty close. That does NOT mean you can bolt the carb in and expect it to ride well without further tuning, but as a starting point its a solid start. The other big sign is the burn colour on the spark plug.
Start the bike up, rev it on the stand to see how it sounds. Make sure its revving keeping in mind the choke will effect things in the first couple minutes of running. If its spluttering and not going anywhere fast, trying going down in the main jet.
When you get back, check the plug against the above chart. The plug check is only really to confirm what you already feel, the way the bike feels under acceleration is your main guide. The correct way to go about changes in jets and needle is ONE setting at time — by this I mean if you ride the bike with a 70 jet and it feels a little lean, go up to a 72 or a Dont jump to an 80, baby steps.
The bike for instance may only be slightly lean on a 70 jet, but an 80 is far too rich. The needle has a small circlip at its flat end the non pointed end which acts as a stopper, as the needle slides through its hole int he end of the slide.
The needle has a number clip settings at its flat end, to which the circlip can be moved to change its setting. Number 1 is a breather between the engine and airbox. It needs to be attached or you'll get problems. Oh right, how is it ment too attach because since I started using it again its just been hanging there..
I took the hose off a little while ago, and the moped felt so much better. Accelerated fast and I could use more throttle before it would feel like its going too flood. Anyone else got any ideas? Really interested too see if anyone knows what the numbers i wrote in the pic are.. Thanks for the reply. How would I go about removing the EGR system?
Is there a step by step guide anywhere? Other Motorcycle Parts. Complete Engines. If your rating is revoked you will lose karma Have you read the ratings guide? Read the Terms of Use! Resend my activation email : Register : Log in. Piaggio zip 50 help with engine. View previous topic : View next topic.
This post is not being displayed. Posted: - 09 Mar Post subject: Piaggio zip 50 help with engine. Back to top. You must be logged in to rate posts. N cee thirty. Ashley Hannah , Oct 1, I have a 76 jet and can ride for 10 mins and then I get the exact same problem. Rich , Oct 2, Any idea what it could be mate? Ashley Hannah , Oct 3, Rich : Ashley putting on exhausts requires an upjet in the carb , its not a put this size in and all will be handy dandy , all scooters will be different due to area they are in the weather and likes all these factors impact the jetting at that time.
There is a sweet spot, its when you have a pull away with a nice crisp mid range and a nice top end , throttle transition should be smooth through this range, no surging , no stuttering - bogging - no holding back then going like the clappers. IF YOUR NOT UPTO THE JOB do not carry on , if you do not jet correctly and the scoot runs to lean you will damage the cylinder - piston - rings or even start to damage the crank and bearing due to the heat produced when running to lean , a local motorbike shop should charge you a couple hours labour and the cost of a jet , they will jet your scoot so it runs correctly , you will need to tell them your having overheat problems due to wrong jet size and you require an up-jet.
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