Plugs in my pilot jets and other jet questions

[Jethro]

Pulled apart the carbs tonight and found something I didn't expect- my pilot jets (fuel not air) all had nice little plugs covering them. Whats that all about? They were definitely put there on purpose, but why? Also, the 125 mains are the stock jets that come with my bike correct? 1981 GS1100EX. Thanks.

[frosty5011]

There was a post on that last week, I think. Yes, the little black plugs are supposed to be there. They prevent fuel from being pulled up through that "tube" in which the pilot jet resides. Instead, fuel is drawn through the other "tube" in which the needle jet is and from there can enter the pilot jet through the little hole which you can see drilled between the two "tubes".

It is supposed to pull fuel through the larger, longer needle jet tube because that one is placed in the exact center of the float bowl.....which guarantees that the fuel level will always be same, no matter if bike is upright or leaning.

That may not have been exactly correct, but that's the jist of it. If I'm wrong, there'll definately be enough folks here to correct me.

[Jethro]

I thought the pilot jet was what maintained the slow speed system?? How does the bike idle if not using the pilot jets? I'm still a little confused.

[Anonymous]

It is using the pilot jets - if you look really carefully (remove the rubber plug) you'll see a tiny hole connecting the tube containing the main jet with the tube containing the pilot jet. The pilot draws its fuel through this.

I recently had carbs apart (3 times!) trying to cure what I figured had to be blocked pilot jets. First time, I thought "Of course they're blocked! Look at those rubber plugs!". Took me a while to spot that little connecting hole. I suppose the pilot jet has to be accessible somehow and the plug is to block off that access.

[frosty5011]

It's kind of hard to visualize without the carbs off, but if the rubber plug was not there to block off fuel access through this smaller tube (in the front), then if you did any prolonged riding downhill.....the bike would run far too rich because the fuel level is higher up front. By the same token, prolonged uphill riding would then be too lean because now the fuel level would be lower in the front area of the fuel bowl.

Only the larger, middle tube is supposed to allow fuel to enter. Since this tube is located in the middle of the bowl.....the fuel level (which is so critical, or else we wouldn't have to adjust our float heighth to within +/- 1mm for bike to run right) is theoretically pretty much the same, regardless of the bikes attitude. Yes, the pilot jet is responsible for the slow speed system, but it draws fuel through the larger tube via the interconnecting little hole which is drilled between the two tubes (about 1/4" down in the larger tube). The big hole at the end of the tube (blocked off by the plug) is really just there to allow you to remove the pilot jet, but plugged during use.

[Jethro]

So then should I replace these plugs during the carb rebuild? The plugs seem dry and if they are supposed to block the fuel, then they are probably not doing a great job of it.

[sharpy]

Plugs

If you look closely on the float bowls there is a step that holds the plugs tight when the bowls are down up tight.

[frosty5011]

You should be okay with the "plugs". Even though they might be a little deformed, they are held in place by the step/potrusion in the bowl that Sharpy mentioned. So, they definately will not fall out.....and once immersed in the fuel-filled bowl for a while, the rubber will swell and seal the hole.

Unless really grossly deformed or dissolved (as from some super industrial strength carb cleaner), I really wouldn't worry about replacing them.