1978 GS550E Mystery Jet Question.

[TheRustySpoke]

Hey all! Wonderful forum full of great resources!! I recently came in possession of a 1978 GS550E! She's in pretty good shape and has about 20,500 miles on her.

I'm an automotive and Motorcycle mechanic out of Medford, MA and I disassembled and dunked the carbs in my ultrasonic cleaner for quite a while. Every channel has been thoroughly cleaned and inspected. I ordered new carb rebuild kits from K&L and the carbs are all put back together, good as new.

She started right back up but im still having a bit of an issue with the fine tuning. There is a mystery jet at the bottom of the Mikuni VM22ss and no matter where I look I cannot find how many turns it needs to be tuned. I originally set them at 2 turns out, the same as the Pilot Air Screws and that doesn't seem to be doing the trick... I got the Shop Service manual after I ripped the carbs apart and i found out that the bottom jet that looks like a secondary pilot air screw is not to be tampered with

here's a pic of what i'm talking about...


any input would be greatly appreciated!

Thanks,
Andy

[7981GS]

This would be the member to send a PM to: http://www.thegsresources.com/_forum/member.php?u=1969

[Pendulum]

That's the pilot fuel screw. And they suck. Really hard.

If your screws haven't been broken off in the body, you're in really good shape. If they have, let us know. There's hope

Screw it in until it GENTLY bottoms, and go 1 turn out. Final adjustments will be made based on plug readings. Turn it out to richen the pilot circuit; in to lean it out.

[TheRustySpoke]

Awesome. Thanks so much for the quick replies! the screws are still in one piece haha. Thanks again guys, I'm gonna get to work on fine tuning this beast.

[OldVet66]

One turn out from lightly seated should get it started. They will most likely end up between there and 3/4 turns out. Tootle around under 25MPH for 15 or 20 min. and take plug readings. Adjust Them a little tweak in-lean out-rich depending on the plug color.

[Pendulum]

You're lucky they weren't broken! Just to be sure, they should be pretty sharp at the tip. If they're not, then make sure there's nothing in the hole.