Thursday 29 August 2013

Cagiva Mito 125 Carb jetting

Cagiva mito 125 for sale here on Ebay UK

Cagiva mito 125 parts for sale here on Ebay UK

see what Carbs are for sale on Ebay UK Here 

jets are M6 on the dellorto 28mm 

A simple equation for figuring you main jet is to multiply dia of carb by 5
and then multiply buy 0.85 for stock 0.9 for bike with sports air filter fitted
0.95 for air filter and exhaust .

28 x 5 x any of 0.85 - 0.90 - 0.95

                                     Cagiva Mito 125 Carb jetting

cagiva mito 125 PHBH  28mm bd card

115 main jet
55 idle jet
55 diffuser jet

rejet to these after you derestrict

120 main jet
60 idle jet
60 diffuser jet

Cagiva Mito 125 Carb jetting

Cagiva Mito 125 Carb jetting

Cagiva Mito 125 Carb jetting


 its always advisable after any change to do a plug chop test (see below) to test combustion conditions , this will give a clear indication of the jetting state , also its recommended to increase jets size 5 points for any sports airfilter or exhaust fitted again do the  plug chop test to ensure correct running conditions 

the purpose of the carburettor is to provide your engine with the correct ratio of fuel and air. Although the carburettor can’t provide the ideal mixture at all loads, the different parts of the carburettor work to try and create this ideal mixture for proper combustion.

The cagiva mito 125 carburettor consists of the following parts:

  • Fuel bowl

  • Shut-off needle

  • Floats

  • Main jet (provides mixing above 1/2 throttle)

  • Pilot jet (provides mixing from idle to 1/4 throttle)

  • Jet needle (regulates flow of the main jet as the throttle is opened; 1/4 to 3/4 throttle)

  • Needle jet (passage to which the jet needle resides)

  • Air screw (adjusts the amount of air from idle to 1/4 throttle)

  • Idle screw (adjust the idle speed)

How does the carburettor mix air and fuel?

Fuel from the tank enters the bowl through a small passage until the floats rise up enough to force the shut-off needle into the passage (prohibiting any more fuel from entering the fuel bowl). The main jet is usually found near the bottom of the fuel bowl. As the piston moves down, it draws air into the cylinder. This air flows through the throat of the carburettor and creates a vacuum which sucks fuel into the cylinder via the main jet.

The mixture screw is able to adjust the air in small amounts in order to fine tune the mixture (usually at idle). Most carburettors require adjustment of this screw and a jet change. When you change a jet, you are simply giving the fuel a smaller or bigger hole to flow through, thus changing the amount of fuel that reaches the cylinder.

What is meant by running rich or running lean?

These terms refer to the amount of petrol being delivered to the engine. If you are running lean, then the ratio of fuel to air is too low, that is, there isn’t enough fuel reaching your engine for the amount of air that is reaching the engine. This can cause the engine to run hotter and leave you with a seized piston. Running rich means that there is too much fuel reaching the engine for the amount of air that is reaching the engine. Running slightly rich is generally acceptable and protects the engine as the excess fuel helps to carry heat out of the engine. If you are running very rich, you will have a very smokey exhaust and performance will suffer.

The ideal ratio of air to fuel is called the stoichiometric ratio.


other jetting articles


How to check Jetting 

    Mark your throttle housing and grip in 1/4 turn increments. Use a marker
    Now get the motor to operating temperature by riding around.
    Once the motor is warm, ride in 2nd and 3rd gear from the low RPM to high RPM. This puts a good load on the motor and is an accurate test of performance. Try to notice if the problem gets worse or better as the motor heats up.
    Now try to locate the throttle opening at which the problem exist.

plug chops are the key to fine tuning the main jet once the other circuits are set:

White to Porcelain / Chocolate / Mocha Brown to Black-Wet
Lean / Perfect! / Rich

Cagiva Mito 125 Carb jetting

A plug chop simply means looking at the sparkplug to determine how you are jetted at a particular throttle stage. The only tricky part is in isolating the throttle stage. Before starting, clean your sparkplug and filter and warm the bike up.

To check the main jet, which operates from 1/2 to full throttle, get the bike up to a steady full throttle or near to it for a good few seconds, then simultaneously pull in the clutch and kill the engine. Don't let the motor drag you to a stop, or fall to an idle, because you want to isolate the plug colour at full throttle.

Get off and check the sparkplug colour It should be a light chocolate colour. If it's white, the air/fuel mixture is too lean and you need a bigger main jet. If it's black or really dark brown, the air/fuel mixture is too rich and a smaller main jet is needed. If you need to change jets, change by one size, and do another run.

You could just dump it all in your ultrasonic cleaner , get one they are excellent 

Cagiva Mito 125 Carb jetting

see more cagiva mito 125 posts here 

BUY our ultimate Cagiva Mito 125 workshop manual bundle HERE 

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