Carb Jet Upgrade And Tuning

sikatri

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Been reading Jenks on tuning the carburetor and changing the jets on my 2005 Thruxton.
From what I’m understanding I should change the jets first and then see if shims are needed. Any experience with this procedure is appreciated.
1C2AD969-F99B-4340-80ED-A3BD90169E21.jpeg3BA2E119-E6CA-4ABD-9A40-64DCEF220ACA.jpeg
The airbox has been deleted and no AI. Essentially bare system.
 

sikatri

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One of the questions I have is does the pilot mixture screw require any specisl tool? Will a screwdriver work?
 

sikatri

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Is a “D tool” necessary for the air fuel mixture adjustment?
 

sikatri

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Step one, get the carburetors in position.80805108-E718-4C56-88BF-62476BE70950.jpeg
 

sikatri

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sikatri

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Both bowl seals look like this, not sure if I can clean them up or...
0140B38D-59A5-43A1-A77B-0C511A4740BC.jpeg
 

sikatri

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Cleaning...78057191-D72C-4E62-A0C6-2A12E214DDCC.jpeg1D08756D-6C7E-4D8B-9D68-FD8E84388867.jpeg
 

sikatri

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I have a question on what an item is on the twin carburetors. There’s a black T-fitting which a black rubber hose connects to. The hose just dangles down and doesn’t connect to anything else. What’s its function? Here’s a parts diagram, it’s 25 on the diagram. The T-fitting is seen in my enlarged photo as well.
329F15C5-AB60-40F1-A9BB-931425F3FB5A.jpegB6EAF960-35BA-4ED1-9EB4-1B48BF66E77B.jpeg
 

sikatri

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I removed the old jets. From what I can read the main jet was 110 and the pilot jet 45. Stock pilot jet should have been 40. Not sure of the manufacture of these jets, picture attached if anyone recognized them.162956B3-4752-4B37-8D71-BB917D478048.jpeg
The jets that came with airbox removal kit are either 35 or 42 pilot jets and a 140 main jet. Since there was a thread here with jet sizes from different manufacturers that showed they are not all the same by number. I don’t know if these are actually comparable, I suspect they are.
 
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sikatri

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One of the jet pairs had more patina/oxidation. Is there an explanation why one pair is different from the other?
070B8D7A-44CF-4381-ABB1-548CDEA9DADA.jpeg
 

Greyfell

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I would like to give a direct answer to your question, but I would be stepping beyond my knowledge level. Instead, let me share the video of a tour of the Holley carburetor plant in Alabama. The tour leader gives a pretty good explanation for two sizes of jets.

 

sikatri

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I’m contemplating what to do with the pilot jets since what I found installed was larger than the one in my new jet kit. Do I go with a 140 main 42 pilot from the kit or do I go with the new 140 main and the old 45 pilot jet? The previous owner had removed the AI and free flow type exhaust. Why 45 pilot jets were installed is still a mystery. I wouldn’t be surprised if the slide was drilled to 3 mm already.
 
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sikatri

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Night ramblings, I’m leaning toward installing the jets from the kit, 140 and 42. I’m also thinking about not looking into what’s in or done to the slide. In other words I’m going to leave it alone until I do the jets and test them out.
 

sikatri

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I need to scrub some spots with a few nylon brushes and see what I can get cleaned. Contemplating which cleaners are the best for the task. Carburetor cleaner or perhaps lacquer thinner...WD-40 too.
 
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sikatri

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New 140 and 42 jets in place. Cleaned as much as I think necessary. Need suggestions on how to clean the bowl seals. I have new seals coming, but it might take a week or more. Both seals have some crud.
8EB082B5-E4AD-4BF9-8D9A-089E9DA55C43.jpeg

2BB8E838-2C54-4FEB-B44F-DBCF8742DD80.jpeg
 

sikatri

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I tried to avoid spraying cleaners to where rubber seals are still inside. The bowls are being cleaned, soaking a bit.
 

sikatri

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Zero’d both pilot mixture screws with the D-tool. I’ll turn them 2.5 turns. It had also been set 2.5 turns.
0A327622-4C82-414F-B5C6-4330ABFA7C33.jpeg
 

Hippy67

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Hey, like all your pics! I'm going through something similar on a 2006 T100. Bought last winter with 8200 miles. Installed Toga silencers and a Uni filter, AI removed. Still have the air box. The bike actually ran pretty good after I ran some Seafoam through the carbs. Opened up the carbs for further cleaning. There were no markings on the jets and I bunged them up some, removing them. Got a 42 pilot and 140 main from Bellacourse. The 140 was way too big, way too rich, the bike wouldn't hardly run above 4500 RPM at full throttle. Put the original main back in and it's back to normal. For me, the 42 pilot seems too big also (again not sure what the original pilot is) So, now I'm waiting on a new 40 pilot jet and a 120 main. I'd be interested to know how the 140 main works for you. With no airbox, it might be just the ticket.
 

sikatri

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Hey, like all your pics! I'm going through something similar on a 2006 T100. Bought last winter with 8200 miles. Installed Toga silencers and a Uni filter, AI removed. Still have the air box. The bike actually ran pretty good after I ran some Seafoam through the carbs. Opened up the carbs for further cleaning. There were no markings on the jets and I bunged them up some, removing them. Got a 42 pilot and 140 main from Bellacourse. The 140 was way too big, way too rich, the bike wouldn't hardly run above 4500 RPM at full throttle. Put the original main back in and it's back to normal. For me, the 42 pilot seems too big also (again not sure what the original pilot is) So, now I'm waiting on a new 40 pilot jet and a 120 main. I'd be interested to know how the 140 main works for you. With no airbox, it might be just the ticket.
From what I’ve read, the 140 main is recommended when you remove the airbox. The airbox removal kit came with a choice of two main jets, 135 and a 140. I’m going with the 140 based on Jenks articles. I’ll keep y’all updated. Your jets were 110 and 40 at factory.
 
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