Basic Jet Question

[bobbfrommn]

Ok this might be really basic but when you guys talk about re-jetting are you talking about the Main jet (number 9 in service manual schematic), Pilot jet in the Jet block (number 13), Pilot Air Jet #1 (number 18) or the Pilot Air Jet #2 (number 20), or do all of them get changed?

I've been assuming it is the Main but wanted to clarify.

 

[maleko89]

That's correct. Most of the time we're talking main jet. PAJ1, PAJ2 and the PFJ rarely need to be changed. Some change PAJ2 to lean out off idle response up to 5000 rpms but is usually only done if there's a big change in altitude or stage 7 carb kit is used. Some have used Mikuni 40's or even 42.5's for the pilot fuel jet but rarely is it needed. They do it because the mixture screws are turned out a long ways....and that's usually due to a plugged or dirty PFJ or the float level is too low.

Mark
#1098

 

[bobbfrommn]

Cool. Can that main jet be done with out taking the carbs out?

I'm thinking I may eventually need to rejet. Mine is running pretty lean. The guy I bought it from said the guy told him it was jetted but from what I'm reading the cobra's require more dinking around and I'm guessing I'll need to switch jets a few times to get it right.

 

[maleko89]

You just need to remove the rack from the boots. Drain the carbs and carefully pull to the left side and then flip upside down. There's a small brass hex bolt on the float bowl cover you remove. Then, loosen the main jet and use a tooth pick to finish unscrewing. Make sure the jet is tight on the pick and remove. Use the toothpick to put the new main jet in. You'll need to sync your carbs when done.

Mark
#1098