Butterfly seal question

[spivey]

Im rebuilding the carbs on my 78E. I know I need to replace the butterfly seals. Here's the question if the seals were leaking which I'm sure they were would that affect the main jet choice. When I broke the carbs down the main jets were 41 40 45 45. The shop that worked on the carbs last were the one's that jetted it. What is the best way to know if I've got each cylinder jetted right. I know I'm going to have to sync the carbs but are there any other tuning tips. I'm also running a kerker header and k&N air filter in the stock airbox.

[Tat2demon]

It would effect everything if its leaking air in. Replace the seals if you think theyre bad then its just a matter of riding and reading the plugs.

http://www.xs11.com/forum/showthread.php?t=85

[donebysunday]

Im rebuilding the carbs on my 78E. I know I need to replace the butterfly seals. Here's the question if the seals were leaking which I'm sure they were would that affect the main jet choice. When I broke the carbs down the main jets were 41 40 45 45. The shop that worked on the carbs last were the one's that jetted it. What is the best way to know if I've got each cylinder jetted right. I know I'm going to have to sync the carbs but are there any other tuning tips. I'm also running a kerker header and k&N air filter in the stock airbox.

Go back to stock jetting and start from there. If you don't know we can help ! What year carbs are these ? How about some pics please ?

[ccogswel]

If I understand what you are saying about the jets I wonder why they put 41/40/45/45????? And I thought the mains for a 78E were bigger then the 40's you have in there now. Or do you mean the pilots? Cause those's sound like pilot jet numbers to me.

[ccogswel]

Ok after checking this http://www.xs11.com/forum/showthread.php?t=73
Your bike should have 137.5 Main Jet and 45.0 Pilot Jet.
If you are sure your talking about main jet size's and those are the numbers on them then I wonder what brand jet they used? Cause every manufacturer that makes jets have different numbers for their jet's. Like the K&L kits from a few years back had the correct number jets listed for our bikes but the holes in the jets weren't the same and caused troubles with idling issue's and such.

Guess we need to know what your bike is doing I.E. like idling issue's or won't rev up. Stuff like that.

[WMarshy]

Im rebuilding the carbs on my 78E. I know I need to replace the butterfly seals. Here's the question if the seals were leaking which I'm sure they were would that affect the main jet choice. When I broke the carbs down the main jets were 41 40 45 45. The shop that worked on the carbs last were the one's that jetted it. What is the best way to know if I've got each cylinder jetted right. I know I'm going to have to sync the carbs but are there any other tuning tips. I'm also running a kerker header and k&N air filter in the stock airbox.

As previously mentioned, they jets you describe are likely the pilots unless you made a typo and meant 140, 145..? The pilots are accessible at the bell mouth of the carb, the main jets are accessible by removing the bowls and are the large round ones. For a '78E the correct jets are 45accessible pilot and 137.5 mains.

[motoman]

As previously mentioned, they jets you describe are likely the pilots unless you made a typo and meant 140, 145..? The pilots are accessible at the bell mouth of the carb, the main jets are accessible by removing the bowls and are the large round ones. For a '78E the correct jets are 45accessible pilot and 137.5 mains.

Correction for ya' WMarshy.......pilot jets are beside the mains inside float bowel.........jets at rear or bell of carb are air jets and are in the 180-210 range depending if early or later carbs.

[WMarshy]

Thanks for the catch, its been a few years since I've been in mine on the bike. My snowmobile pilots are in the bell mouth.

[bikerphil]

Those removable jets in the bell are the air pilot circuit jets, the main air jets in the bell are the pressed in ones.

[skids]

and those pressed-in jets tend to plug-up. I believe they feed air to the sides of the emulsion tubes. Plug it up and your carb is rich in the mid-top end.

[Schming]

and those pressed-in jets tend to plug-up. I believe they feed air to the sides of the emulsion tubes. Plug it up and your carb is rich in the mid-top end.

Correct, and easily missed whilst cleaning