The Sportster and Buell Motorcycle Forum - The XLFORUM®
 

Go Back   The Sportster and Buell Motorcycle Forum - The XLFORUM® > SPORTSTER MOTORCYCLE FORUM > Sportster Motorcycle Era Specific and Model Specific > Ironhead Sportster Motorcycle Talk (1957-1985)
XLF Blogs XLF Arcade XLF Disclaimer/Privacy Statement/Terms Of Use

Notices

Ironhead Sportster Motorcycle Talk (1957-1985) For all those that wanna talk about Ironhead Sportster Motorcycles

Active Threads
0 1968 ex barn dweller thread
Last Post: fernf5
Posted On: 3 Minutes Ago
Replies: 155
Views: 13,253
0 Ford CEO Jim Farley nominated to Harley-Davidson board of directors
Last Post: Sasnak75
Posted On: 10 Minutes Ago
Replies: 13
Views: 657
0 Official XL Forum Random Image Thread (NO NUDITY!)
Last Post: maltesefalcon
Posted On: 14 Minutes Ago
Replies: 50,356
Views: 8,268,212
0 Hammer 1275 clang noise, slow oil feed, kinked crankcase vent.
Last Post: BestCoastXL
Posted On: 23 Minutes Ago
Replies: 450
Views: 15,129
0 What to do now? Ironhead clutch hub nut stripped
Last Post: Andy Hog
Posted On: 23 Minutes Ago
Replies: 9
Views: 370
0 Mimi the Deerslayer: the triple threat
Last Post: hbkeith
Posted On: 27 Minutes Ago
Replies: 43
Views: 3,606
0 Ironhead Exhaust Poll
Last Post: Serious Blac
Posted On: 44 Minutes Ago
Replies: 215
Views: 61,121
0 Backfiring
Last Post: IXL2Relax
Posted On: 45 Minutes Ago
Replies: 36
Views: 1,899
0 WTB 04-06 intake manifold
Last Post: beardo
Posted On: 1 Hour Ago
Replies: 7
Views: 225
0 S&S Super B help
Last Post: sungod
Posted On: 1 Hour Ago
Replies: 8
Views: 362
0 xl1200T
Last Post: SLW210
Posted On: 1 Hour Ago
Replies: 2
Views: 110
0 S&S Super E
Last Post: thecarfarmer
Posted On: 2 Hours Ago
Replies: 16
Views: 933
0 Hottie of the day, no nudity.
Last Post: cal43
Posted On: 2 Hours Ago
Replies: 28,407
Views: 3,022,855
0 Hot Chicks on Hot Bikes
Last Post: cal43
Posted On: 2 Hours Ago
Replies: 11,896
Views: 2,528,381
0 This is gonna hurt.
Last Post: Stairman
Posted On: 3 Hours Ago
Replies: 8,444
Views: 1,871,936
0 "The Blues" thread!
Last Post: Graywolf
Posted On: 3 Hours Ago
Replies: 996
Views: 113,200
0 ....1
Last Post: Graywolf
Posted On: 3 Hours Ago
Replies: 6,033
Views: 357,690
0 Corona Virus
Last Post: b0fh
Posted On: 6 Hours Ago
Replies: 1,628
Views: 159,519
0 2018 Iron 1275 Project
Last Post: Turbo Sporty 48
Posted On: 12 Hours Ago
Replies: 31
Views: 3,511
0 Keep & Kill
Last Post: Graywolf
Posted On: 13 Hours Ago
Replies: 21,387
Views: 1,265,116
0 Do you blow dry your ride after wash
Last Post: Hippysmack
Posted On: 14 Hours Ago
Replies: 176
Views: 20,855
0 final drive front sprocket change
Last Post: kitabel
Posted On: 14 Hours Ago
Replies: 6
Views: 472
0 Do you blip the throttle when downshifting?
Last Post: Ireeman
Posted On: 15 Hours Ago
Replies: 477
Views: 91,044
0 What Is the Advantage - Shovster?
Last Post: Chuckthebeatertruck
Posted On: 15 Hours Ago
Replies: 85
Views: 5,964
0 Non-Starter, Compression Test Results
Last Post: GA_Ironhead
Posted On: 17 Hours Ago
Replies: 22
Views: 923
0 Iron 1966 XLRTT
Last Post: brucstoudt
Posted On: 17 Hours Ago
Replies: 186
Views: 42,494
0 Magneto Sportster's 1964 XLH Restoration Project
Last Post: brucstoudt
Posted On: 18 Hours Ago
Replies: 53
Views: 7,708
0 Swing arm bearing change
Last Post: SportsterXLCH1967
Posted On: 19 Hours Ago
Replies: 7
Views: 360
0 Peanut, 3.3 or 4.5 gas tank ?
Last Post: IXL2Relax
Posted On: 20 Hours Ago
Replies: 261
Views: 79,553
0 What did you do to your EFI Sporty today?
Last Post: Maxwell#256
Posted On: 20 Hours Ago
Replies: 4,006
Views: 827,593
More...
Members Birthdays
Reply
 
Share Thread Tools Display Modes
  #11  
Old 13th February 2021
sungod's Avatar
sungod sungod is offline
XL FORUM TEAM MEMBER
 
Join Date: Feb 2009
Location: ny
Posts: 247
Sportster/Buell Model: sportster xlch
Sportster/Buell Year: 1970
Sportster/Buell Model #2: sportster xlh
Sportster/Buell Year #2: 73
Other Motorcycle Model: 99 inch sportster
Other Motorcycle Year: 2003
Reputation: 25936
sungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to all
Default mikuni air jet

I have around 5 Mikuni vm38 carbs and all have .5 air jets. The air jet adds air to the high range of throttle opening when the main jet is active. Multiple sizes are available. The jet is very small and easily stripped if the wrong screwdriver size and/or tip profile is used.Gunsmith style screwdrivers work best.
Reply With Quote
  #12  
Old 13th February 2021
kitabel kitabel is offline
Chief Harley Engineer
 
Join Date: Oct 2019
Posts: 549
Sportster/Buell Model: 883 Evo
Sportster/Buell Year: 1989
Reputation: 169470
kitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant futurekitabel has a brilliant future
Default

1. use the .5 (it's .5mm or .020"), it partially controls the A:F curve with rising RPM.
2. A Mikuni requires a strong vacuum (behind the slide) to pull fuel/air mix from the starter jet.
Reply With Quote
  #13  
Old 18th February 2021
ryder rick's Avatar
ryder rick ryder rick is offline
Senior Master Custom Bike Builder
 
Join Date: Jun 2008
Location: Cornelius, OR
Posts: 9,627
Reputation: 1215694
ryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond reputeryder rick has a reputation beyond repute
Default

So this jet is in the air horn?(down at the bottom)

That jet supplies air to the emulsion tube and will control the fuel curve. just like the air bleed on a S&S.
I believe the smaller jet is richer/sooner
__________________
Ryder Rick "I know right from wrong, but sometimes, wrong feels right"
Reply With Quote
  #14  
Old 19th February 2021
Scuba10jdl's Avatar
Scuba10jdl Scuba10jdl is offline
Senior Chief Harley Engineer 1st Class
 
Join Date: Dec 2010
Location: Columbus, Ohio
Posts: 1,394
Sportster/Buell Model: XLH883/1250
Sportster/Buell Year: 2002
Sportster/Buell Model #2: XLCH 1000
Sportster/Buell Year #2: 1972
Reputation: 549790
Scuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond reputeScuba10jdl has a reputation beyond repute
Default

Quote:
Originally Posted by ryder rick View Post
So this jet is in the air horn?(down at the bottom)

That jet supplies air to the emulsion tube and will control the fuel curve. just like the air bleed on a S&S.
I believe the smaller jet is richer/sooner


The air jet is number 12 in that picture. And yes, smaller air jet correlates to richer mixture. Less air allowed through the air jet creates a higher vacuum at the emulsion tube, thus pulling more fuel.
__________________
[IMG]http://i.imgur.com/Oe4Ttw0.png[/IMG][IMG]https://i.imgur.com/AFv3AMo.jpg?1[/IMG]
2002 XLH883/HAMMER1250 - 1972 XLCH 1000 - Few things in life are as satisfying as riding a Sportster with no destination in mind.
Reply With Quote
  #15  
Old 24th February 2021
sungod's Avatar
sungod sungod is offline
XL FORUM TEAM MEMBER
 
Join Date: Feb 2009
Location: ny
Posts: 247
Sportster/Buell Model: sportster xlch
Sportster/Buell Year: 1970
Sportster/Buell Model #2: sportster xlh
Sportster/Buell Year #2: 73
Other Motorcycle Model: 99 inch sportster
Other Motorcycle Year: 2003
Reputation: 25936
sungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to all
Default mikuni air jet

The air jet mirrors the main jet and enhances fuel emulsion at full throttle. Starting is all about the pilot jet and float level and of course slide opening (need that vacuum).
Pilot jet selection should be done on a hot engine at 1/8 throttle position.
Adjust air screw for highest rpm if:
less than 1 turn out= lean remedy larger pilot jet
more than 2 turns out= rich remedy smaller pilot jet
Raise float level 1/2mm and check starting
As stated slide closed.
Reply With Quote
  #16  
Old 24th February 2021
Serious Blac's Avatar
Serious Blac Serious Blac is offline
Flat Track Champion
 
Join Date: Aug 2017
Posts: 610
Sportster/Buell Model: xls roadster
Sportster/Buell Year: 1982
Other Motorcycle Model: Oh yeah!
Reputation: 108620
Serious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud ofSerious Blac has much to be proud of
Default

The air jet controls the fuel slope AT WIDE OPEN THROTTLE in the same way the main jet does. Getting it right will make your carburation sweeter but you could probably get along with the wrong one. It would be nice if someone who has a Sudco kit could tell us what air jet they use. Most of the info on the internet is confusing to say the least.
__________________
The Devil is in the detail.
Reply With Quote
  #17  
Old 24th February 2021
sungod's Avatar
sungod sungod is offline
XL FORUM TEAM MEMBER
 
Join Date: Feb 2009
Location: ny
Posts: 247
Sportster/Buell Model: sportster xlch
Sportster/Buell Year: 1970
Sportster/Buell Model #2: sportster xlh
Sportster/Buell Year #2: 73
Other Motorcycle Model: 99 inch sportster
Other Motorcycle Year: 2003
Reputation: 25936
sungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to allsungod is a name known to all
Default mikuni air jet

I found the Victory Library Mikuni Tuning for Harley Davidson much more informative than the other manuals. A real in depth examination of tuning the VM 38 and by the way a recommended air jet size of .05.They sell a PDF for I think $10.
Reply With Quote
Reply

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT +1. The time now is 16:08.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
XL Forum® - Linson Media LLC