Carb ID and spec questions

[jonathacvb]

So I pulled apart my carb today to review its condition. Previous owner claimed it was rebuilt and cleaned. It appears this was partially true but was just not done thoroughly.

Using the instructions found HERE I was able to get along quite well. However, upon completion and consulting THIS spec chart I seem to not have all the parts out yet. Also, some of my parts do not entirely match the specs on the chart.

Could someone help me identify the parts in the photo below?

1. Float needle?
2. unclear
3. Main Jet? (currently all 4 are 115)
4. unclear
5. Pilot jet? (currently 37.5)
6. Pilot air? (currently 185)
7. unclear


Now, according to that chart I should still need to pull a 'Start Jet, Main Air, and Throttle Valve'. What am I missing here?

Also, does anyone have any remarks on a good way to extract a stubborn Pilot Jet?

Thanks in advance,
Jonny

[Radioguylogs]

1. Float Needle
2. Float Needle Seat
3. Main Jet
4. Emulsion Tube
5. Pilot Jet
6. Air Pilot Jet
7. Idle Mixture Screw

I thought the Start Jet is buried behind the choke plunger - not usually removable.

Not familiar with a Main Air Jet, but the numbers in that chart are the numbers you would find for #6 in the above list- must be the same thing.

I have to guess the Throttle Valve would be the brass disc (Butterfly) flapper in the throat. I don't know why there would be different butterfly discs.

[jonathacvb]

Ok, so perhaps then I have pulled out all I can and can continue with cleaning. Any thoughts on the pilot jet being 37.5 as opposed to 42.5 ?

[Radioguylogs]

I can't think of any reason one would choose a smaller pilot jet.

You don't show what year your carbs are, but it's good to go with the information in the service manual. Most are 42.5.

[jonathacvb]

I can't think of any reason one would choose a smaller pilot jet.

You don't show what year your carbs are, but it's good to go with the information in the service manual. Most are 42.5.

Unless the carbs were previously swapped, they are from a 1980 XS1100 SG.

I've been cleaning and slowly re-assembling the parts but have come to a minor impasse.

MAIN JETS
PRESCRIBED: 110(1&4) 120(2&3)
ACTUAL: 115 (all 4)

PILOT JETS
PRESCRIBED: 42.5
ACTUAL: 37.5

JET NEEDLE
PRESCRIBED: 5GL16
ACTUAL: 5GLZ18

Also, The circlip on the needle is set to the LOWEST setting (closest to needle point)

I don't know a lot about how a carburetor operates and so I am hoping to figure out if the current configuration is OK here before I re-assemble any further

[cajun31]

Unless the carbs were previously swapped, they are from a 1980 XS1100 SG.

I've been cleaning and slowly re-assembling the parts but have come to a minor impasse.

MAIN JETS
PRESCRIBED: 110(1&4) 120(2&3)
ACTUAL: 115 (all 4)

PILOT JETS
PRESCRIBED: 42.5
ACTUAL: 37.5

JET NEEDLE
PRESCRIBED: 5GL16
ACTUAL: 5GLZ18

Also, The circlip on the needle is set to the LOWEST setting (closest to needle point)

I don't know a lot about how a carburetor operates and so I am hoping to figure out if the current configuration is OK here before I re-assemble any further

Original carburetors for the 1980 XS1100 SG did not come with adjustable jet needles. Someone has swapped those carbs to an earlier version. Post pictures of the entire carb bodies, tops and bottoms and side views. We may be able to identify them from there.

[jonathacvb]

Original carburetors for the 1980 XS1100 SG did not come with adjustable jet needles. Someone has swapped those carbs to an earlier version. Post pictures of the entire carb bodies, tops and bottoms and side views. We may be able to identify them from there.

Yes, that’s what I thought based on previous reading and is why I asked.

The carbs I pulled apart from a salvage bike had the same adjustable needles

[cajun31]

Yes, that’s what I thought based on previous reading and is why I asked.

The carbs I pulled apart from a salvage bike had the same adjustable needles

Those are an early version of the later carbs, if that makes sense. The needles that you say are adjustable, although I can't really see it well, but one picture you posted has the top of the needle With the plastic ring on it. I don't believe that ring can be adjusted. It is simply attached to hold the needle in place when it is all put back together with the plate on top of it and screwed down in place. The reason I say these are the early version of the later carbs is because of the plugs in the pilot jet towers. The jets get their fuel from the main jet towers. You will find a small hole bored between the two towers and is the reason your pilot jets are 37.5 rather than 42.5. Clean them, pre synch them with the bread tie method posted under maintenance and then synch them on the bike and you will be good to go with what you have.

[jonathacvb]

Thanks for the info, this is helpful. Here is a closer look at the needle..

[cajun31]

Thanks for the info, this is helpful. Here is a closer look at the needle..

It does look like it can be adjusted. Try it like it is now not making changes because that was the way it was before. Cleaning the carbs is probably all you need.

[Radioguylogs]

Those are an early version of the later carbs, if that makes sense. The needles that you say are adjustable, although I can't really see it well, but one picture you posted has the top of the needle With the plastic ring on it. I don't believe that ring can be adjusted. It is simply attached to hold the needle in place when it is all put back together with the plate on top of it and screwed down in place. The reason I say these are the early version of the later carbs is because of the plugs in the pilot jet towers. The pilot jets get their fuel from the main jet towers. You will find a small hole bored between the two towers and is the reason your pilot jets are 37.5 rather than 42.5.

I added one word to the above for clarification.

Someone correct me if I am mistaken:

I think the size of the pilot jet is same regardless of the tunnel between the main jet tower and the pilot jet tower. I still think 37.5 doesn't make sense.

Of course the main jet is bigger if there is a tunnel between the main jet tower and the pilot jet tower (137.5 vs 110/120), since the pilot has to drink through the main jet. The pictures above must have this tunnel since the pilot tower has the rubber plug.

Regarding the needle, I would put the e-clip clip back in the middle slot to restore the factory needle setting.

[cajun31]

I added one word to the above for clarification.

Someone correct me if I am mistaken:

I think the size of the pilot jet is same regardless of the tunnel between the main jet tower and the pilot jet tower. I still think 37.5 doesn't make sense.

Of course the main jet is bigger if there is a tunnel between the main jet tower and the pilot jet tower (137.5 vs 110/120), since the pilot has to drink through the main jet. The pictures above must have this tunnel since the pilot tower has the rubber plug.

Regarding the needle, I would put the e-clip clip back in the middle slot to restore the factory needle setting.

I have run across these carbs one time. I can't really remember what size the pilots were on those. I was just rebuilding them just to resell them. Which I did. I wish at this point I could remember but it has been too long. I was rebuilding several sets and if memory serves me correctly those carbs were essentially the same as the others other than the plugs over the pilot jet towers. It will all boil down to how the bike idles and whether they can be properly tuned. I wasn't sure about the needles.

[jonathacvb]

Thanks for the input fellas, it’s gonna take me reading it all a number of times to understand it clearer. However, does it make sense that the needle has been adjusted to compensate for the smaller pilot jets?

also, thinking about it. All the jets are brand new (from what my limited experience tells me). However, one of the jets was seized and so it never got replaced. I was able to extract it and have any extra from a salvage bike I was planning to use. I’m not sure this plays into it at all but it begs the question.. do jets need to be replaced occasionally or can you use them for a long time provided there maintained well?

[Radioguylogs]

Jets never wear out as long as they not cleaned abusively (drill bit, hard wire, etc.)

[Tonyxs11]

looks like the needle clip is in the middle slot, but check the plastic spacer under the clip if it has a spike coming off it ? if it does make sure when you fit it the spike goes in the hole in the piston slide, if it doesn't go in the needle will be lifted too high and run way rich.