85 GS 450 carb question, rubber plug in each carb blocking a jet?

[83Rabbit]

Hi all, new to the GS's. Have owned and worked on plenty of bikes but just picked up my first gs the other day.
It has a bad intermittent hesitation that comes and goes under load, similar to that of a clogged jet or improperly adjusted carb.

I pulled the carb down and theyre in need of a good soaking and cleaning.

My question is, what are the rubber plugs for that are plugging off what looks like a smaller jet immediately beside the main jet??? One of the carbs had a plug the other didn't. I'm assuming there should be a plug in each? What do they do? and what would the repercussions be of not running them in the carbs? (could this be part of my missfire/hesitation problem?)

Any help would be greatly appreciated. Ive never seen rubber plugs blocking a fuel passage before...

Thanks in advance!!!!

[Steve]

First of all,


Second, yes the rubber plug is VERY necessary.

The pilot fuel jet (the one hidden by the rubber plug) obviously needs that area to get threaded in and out, but it receives its fuel supply via the main jet, which is right next door. If you look carefully, you will see a small hole between the two areas. If you do not put the rubber plug back in, the bike will start and idle just fine, it might even work OK at low throttle openings, However, once you open the throttle to the point where you get into the needle circuit (which also draws its fuel through the main jet), it will also draw fuel through that transfer hole, which is unmetered, causing too rich a mixture. When you finally get to wide open throttle, you will be drawing fuel through the main jets and the transfer hole, again, too rich a mixture. Simply installing the rubber plug makes it all happy.




.

[83Rabbit]

Makes sense... Was wondering why my new plug looked VERY clean in that cylinder.... like it was being washed with fuel....

Gotta love previous owners who pay no attention to small bits while tearing things down!

Thanks for the quick reply! Ill pick one up from the local cycle salvage yard along with the tach cable I need and hopefully get this bad boy running well asap.

[Steve]

Thanks for the quick reply!

Yet another one that thinks 18 minutes for a response is "quick".

.