GS650 Carb Pilot Jet question

[Guest]

So I needed to replace the #1 & #2 carb bodies on this old basket case I am working on. I obtained new bodies but what I am noticing that the bodies have a minor difference. The bodies have small holes (passages) from under the pilot jets that open into the carb throat. The old ones do not. After inspecting all of the old bodies a a couple have the holes, a couple dont. Can someone explain this and does it matter that the newer bodies have this small difference? I am used to the old yamaha maxim I worked on before this GS and all yamaha bodies had the passage under the pilot jet.

[Steve]

I have also noted that hole with some of the carbs in my stash. Have not yet figured out the pattern, though.

Some of my carbs have come from 850s, some from 750s and some from 650s.

.

[tkent02]

Transition ports, they help the engine go smoothly from idle to a tiny bit of throttle.

Or something like that. Google it and read all about it. Some carbs have two or three ports, some don't. Super secret carburetor engineer stuff I guess.

You should be able to tune the carbs to work fine even if these ports are not all the same.

[junkmn]

Thanks for the reply anf the hint on what to search for. Found this article/link that seems to have lots of good info

http://www.mychinamoto.com/forums/showthread.php?344-CV-carburettors-They-re-different

[tkent02]

I'd read a few more articles, that one is kind of funny...

[Steve]

Transition ports, they help the engine go smoothly from idle to a tiny bit of throttle.

Or something like that. Google it and read all about it. Some carbs have two or three ports, some don't.

Not sure we are talking about the same ports, Tom. The transition ports that I have seen are at the top of the carb throat, up near the top edge of the throttle butterfly. Usually two, sometimes three, but they are up there, in-line with the opening at the bottom of the mixture screw.

The hole that 'junkmn' is asking about is in the bottom of the throat, directly above the pilot jet. It almost looks like someone was drilling the jet and overshot, putting a hole in the bottom of the throat. If it were just one or two carbs, I would believe the "oops" possibility, but I have over half a dozen carbs with that hole.

.

[junkmn]

Yep not asking about the transition ports. The holes I am wanting to know about are at the bottom of the carb throat above the pilot jet.