kirky
CB750 Addict
i am wanting to know if the main jet has anything to do with cold starting, my 750FZ has 102 main jets but they should be 75's and i find it very difficult to start it in cold weather
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main jet
- Thread starter kirky
- Start date
The main jet shouldn't be pulling any fuel at idle. The slides are closed and the needle is sticking the whole way through its needle jet, closing off the path for fuel to flow through the main jet.
Your pilot jet is the important jet for cold starting, and it's also the jet that most frequently gets dirty and clogged in a carburetor. Arguably it's also the most common starting problem for carbureted bikes. It is, however, definitely not the only problem that can cause poor cold starting. Another fairly common one is vacuum leaks.
Why are your main jets so far off?
Your pilot jet is the important jet for cold starting, and it's also the jet that most frequently gets dirty and clogged in a carburetor. Arguably it's also the most common starting problem for carbureted bikes. It is, however, definitely not the only problem that can cause poor cold starting. Another fairly common one is vacuum leaks.
Why are your main jets so far off?
kirky
CB750 Addict
hi thanks for reply. the clymer and haynes manuals i have don't mention the JDM 750FZ for the carb jets. when i had them re-furbished i thought they had the wrong jets in the mains and got the chap to put 102's in. i put all new rubbers on and my mate vacuumed them in. i later found out it wouldn't rev over 5000rpm and a lot of peoples thoughts were electrical because of a cracked coil and melted cdi's. after sorting the electrics it was still the same. by trial and error i found out that by leaving the little plate off the air filter it cured that. it was bogging out by overfueling , then i discovered the JDM air box was designed to match the 75's for emissions. the only problem i have is cold starting in winter . i have also used one of those awkward bent screw driver adjusting tools to try and get it to start more easily. when i started it a few days ago i used a hairdryer blowing hot air into the air filter
i am thinking of getting them off in the summer when the rubbers are easier to work and putting the 75's back in and setting up the screws on the bench but i am not looking forward to this job again. i just wondered if the mains came into play with the other jets like i think they can on some other carbs, cheers.
i am thinking of getting them off in the summer when the rubbers are easier to work and putting the 75's back in and setting up the screws on the bench but i am not looking forward to this job again. i just wondered if the mains came into play with the other jets like i think they can on some other carbs, cheers.
