The Sportster and Buell Motorcycle Forum - The XLFORUM®
 

Go Back   The Sportster and Buell Motorcycle Forum - The XLFORUM® > SPORTSTER MOTORCYCLE FORUM > Sportster Motorcycle Motor / Engine > Sportster Motorcycle Motor - Top End
XLF Blogs XLF Arcade XLF Disclaimer/Privacy Statement/Terms Of Use

Sportster Motorcycle Motor - Top End Discuss Sportster Motorcycle Top End issues. Rockerboxes, Valves, Cylinders, Pistons, Rings, Lift Rods, etc...

Active Threads
0 Keep & Kill
Last Post: Graywolf
Posted On: 7 Minutes Ago
Replies: 14,287
Views: 802,878
0 opinion time (bike broke again)
Last Post: mrbreezeet1
Posted On: 1 Hour Ago
Replies: 3
Views: 34
0 OEM front brake pads vs EBC double h
Last Post: Nibelungen
Posted On: 1 Hour Ago
Replies: 9
Views: 168
0 What weight oil?
Last Post: brianbbs67
Posted On: 2 Hours Ago
Replies: 13
Views: 495
0 Grüezi aus der Schweiz
Last Post: brianbbs67
Posted On: 2 Hours Ago
Replies: 12
Views: 425
0 How much is a late 60's early 70's Sportster worth?
Last Post: brianbbs67
Posted On: 2 Hours Ago
Replies: 10
Views: 516
0 Share your Man Cave Garage ideas
Last Post: NGOT8R
Posted On: 3 Hours Ago
Replies: 28
Views: 470
0 1974 35mm fork boots
Last Post: brianbbs67
Posted On: 3 Hours Ago
Replies: 3
Views: 113
0 Seeking advice on shorter rear shocks
Last Post: Gulf Coaster
Posted On: 3 Hours Ago
Replies: 2
Views: 47
0 Hot Chicks on Hot Bikes
Last Post: hammer6315
Posted On: 4 Hours Ago
Replies: 10,383
Views: 1,816,677
0 screaming eagle cams
Last Post: 60Gunner
Posted On: 4 Hours Ago
Replies: 2
Views: 55
3 Shaky Dave Recovery
Last Post: Martysf
Posted On: 5 Hours Ago
Replies: 49
Views: 7,392
3 Wtb, Wts, Wtt, Wtg (Ironhead)
Last Post: dodgetrucken
Posted On: 5 Hours Ago
Replies: 54
Views: 240,308
0 Hottie of the day, no nudity.
Last Post: trainman
Posted On: 5 Hours Ago
Replies: 14,965
Views: 1,414,666
0 Average age of the Ironhead forum users
Last Post: Kingrabbit
Posted On: 5 Hours Ago
Replies: 448
Views: 89,009
0 Powerraythor conversion
Last Post: ferretface
Posted On: 6 Hours Ago
Replies: 2
Views: 185
0 Best Battery Maintainer and/or Booster?
Last Post: 60Gunner
Posted On: 6 Hours Ago
Replies: 19
Views: 561
0 Full face, Half or skull cap?
Last Post: mikeLI_77
Posted On: 6 Hours Ago
Replies: 502
Views: 93,273
4 The no-debate OIL POLL
Last Post: boomerguy
Posted On: 6 Hours Ago
Replies: 267
Views: 69,545
0 Official XL Forum Random Image Thread (NO NUDITY!)
Last Post: hammer6315
Posted On: 6 Hours Ago
Replies: 45,476
Views: 7,178,630
0 This week on Craig's list
Last Post: Maxeffort
Posted On: 6 Hours Ago
Replies: 4,447
Views: 543,441
0 C.O.B.B. CBD oil
Last Post: gravydog
Posted On: 7 Hours Ago
Replies: 10
Views: 210
0 “Super Quiet” or “Interconnected” exhaust
Last Post: Magneto Sportster
Posted On: 7 Hours Ago
Replies: 4
Views: 149
0 Which Battery?
Last Post: 60Gunner
Posted On: 7 Hours Ago
Replies: 41
Views: 13,424
5 HAMMER vs NRHS vs S&S Conversion Kits
Last Post: Bulpitt
Posted On: 8 Hours Ago
Replies: 58
Views: 5,316
0 Battery self-discharge
Last Post: sportsterdoc
Posted On: 8 Hours Ago
Replies: 11
Views: 1,500
0 Duplicate Sensor Plugs on my '08
Last Post: DeadeyeRich
Posted On: 8 Hours Ago
Replies: 2
Views: 64
0 Huge cock up (XR1200 Clutch Mod)
Last Post: wedge
Posted On: 8 Hours Ago
Replies: 69
Views: 2,828
0 Transformer XR1200
Last Post: Davo_137
Posted On: 9 Hours Ago
Replies: 119
Views: 10,177
0 Benelli tank on 79’ sportster
Last Post: bustert
Posted On: 9 Hours Ago
Replies: 7
Views: 260
More...
Members Birthdays
Sponsored Links
Reply
 
Share Thread Tools Display Modes
  #1  
Old 22nd August 2019
60Gunner's Avatar
60Gunner 60Gunner is offline
Chief of Security
 
Join Date: Sep 2017
Location: United States
Posts: 2,109
Sportster/Buell Model: 1200/1250C
Sportster/Buell Year: 05
Reputation: 2316555
60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute
Default Bigger valves

Is there any advantage to using bigger valves than already in the xb heads? Especially on stock 1200 pistons/cylinders?
__________________
05 1200/1250C/Hammer 570 Cams/E1 clutch kit +15% spring
TC88A Gunner's V00D00 map/DCPR7E/Taylor Pro 8mm
S&S Premium Lifters/KhromeWerks HP Plus 3" slip ons
HSR42 25 pilot 2 turns Y8 needle jet 97 needle 2nd groove 170 main
Dragtron II AC K&N filter/VR1 20W50/Spectro 85wt Primary Oil

Reply With Quote
  #2  
Old 22nd August 2019
Maxeffort's Avatar
Maxeffort Maxeffort is offline
Momentary Specialist
 
Join Date: Aug 2016
Posts: 604
Sportster/Buell Model: XL1200
Sportster/Buell Year: 1996
Other Motorcycle Model: ST1100
Other Motorcycle Year: 1999
Reputation: 908882
Maxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond reputeMaxeffort has a reputation beyond repute
Default

this is a good question.

On automotive heads, bore size and head chamber size limits the effectiveness of larger valve after a point. If the valve is getting close to the edge of either it hurts airflow and CD. Some compensation is steeper valve seat angle, the actual seat and the top cuts into the chamber. Altering valve inclined angle can help. (Gets the valve away from the edge, but much more work) A bigger valve without the port work rarely is beneficial either. (Only if the port and throats are already too big for the valve)
__________________
Sleepy Labeef rides again!
Reply With Quote
  #3  
Old 22nd August 2019
bustert's Avatar
bustert bustert is offline
XL FORUM TEAM MEMBER
 
Join Date: Jul 2008
Posts: 9,628
Sportster/Buell Model: 1200s
Sportster/Buell Year: 2001
Sportster/Buell Model #2: xlch
Sportster/Buell Year #2: 1974
Reputation: 2763800
bustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond reputebustert has a reputation beyond repute
Default

ole oilfield saying
"if you can't fix it, get a bigger hammer"
Reply With Quote
  #4  
Old 22nd August 2019
60Gunner's Avatar
60Gunner 60Gunner is offline
Chief of Security
 
Join Date: Sep 2017
Location: United States
Posts: 2,109
Sportster/Buell Model: 1200/1250C
Sportster/Buell Year: 05
Reputation: 2316555
60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute
Default

I was talking to someone about this the other day when we were discussing cleaning up the heads and blending the seats on the intake to improve flow and he was wondering about bigger valves.
He has stock 1200 pistons/cylinders and I think 551 cams. Maybe N4s.
Sorry for the double threads. Not sure what happened.

My thinking is you would lose velocity.
Reply With Quote
  #5  
Old 22nd August 2019
Toejam503's Avatar
Toejam503 Toejam503 is offline
Air-Cooled Forever
 
Join Date: May 2010
Location: Dakota Territory
Posts: 2,755
Sportster/Buell Model: XL 1200 C
Sportster/Buell Year: 2006
Sportster/Buell Model #2: (Prev.Own)XLH Milw.Spec.
Sportster/Buell Year #2: 1981
Reputation: 5022919
Toejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond reputeToejam503 has a reputation beyond repute
Default

AFAIK, using larger valves depends on the head design. If the head was designed for street use, even with porting, larger valves will probably decrease air flow. Going to 3-4 valves per cyl. will increase flow. Again, head design is the major factor.
Reply With Quote
  #6  
Old 22nd August 2019
60Gunner's Avatar
60Gunner 60Gunner is offline
Chief of Security
 
Join Date: Sep 2017
Location: United States
Posts: 2,109
Sportster/Buell Model: 1200/1250C
Sportster/Buell Year: 05
Reputation: 2316555
60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute
Default

I think the valves on these heads are plenty big enough. Especially on 1200 flat tops. You would want to increase velocity not lose it. That's my amateur thinking.
Reply With Quote
  #7  
Old 22nd August 2019
60Gunner's Avatar
60Gunner 60Gunner is offline
Chief of Security
 
Join Date: Sep 2017
Location: United States
Posts: 2,109
Sportster/Buell Model: 1200/1250C
Sportster/Buell Year: 05
Reputation: 2316555
60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute60Gunner has a reputation beyond repute
Default

I just want to steer him down the right path because he's not happy. He rode my bike yesterday and I thought he was coming off the back. Now mine is nothing spectacular but it is a spunky little street bike.
I didn't ride his. He came in his car but he said mine has way more power which just made him more determined to make improvements and asked about headwork and bigger valves.
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



Sponsored Links
All times are GMT +1. The time now is 08:35.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
XL Forum® - Linson Media LLC