Post your carb tuning specs!

[ignition]

Have you finally dialed in your carb settings!?! Lets start a thread listing your own carb sepcs!

Give as much specific information as you can, especially in regards to Airbox and Exhaust system. There are a lot of variables to consider, but hopefully this will become a guide in the future for certain combinations that work well.

If I left out a bullet point that you think is important, let me know and I'll add it so members can just cut and paste the spec list and enter their own info.

Admin will delete any non-conforming posts in this thread. So if you have a question about a particular setup on a members machine, just PM them directly!

Please use the following format:

• Year:
  
• Geographic Location and Altitude:
  
• Carb set: BS38, BS34, VM34, VM36, or other. List year of bike that the set is from if it doesn't match the year of your machine.
  
• Airbox: Stock, K&N, Generic Pod
  
• Exhaust: Stock, stock header w/ mufflers, drag pipes.
  
• Performance Mods:
  
• Main Jet:
  
• Pilot Jet:
  
• Needle:
  
• Needle Position:
  
• Mix screw: In turns out.
  
• How many times you've had the carbs on and off the bike!:
  
  
• Notes: List anything else that you believe to be relevant about your machine!!!
  

[detroitmuscle07]

Year: 1974
Location: Pensacola, FL
Carb Set: 1973 BS38's
Airbox: Deleted with pods
Exhaust: Drag pipes w/washer baffles
Performance Mods: Mikes 750cc kit, Pamco Ignition
Main Jet: 135
Pilot Jet: 45
Needle: Y-22 that came with rebuild kit
Needle Jet: ?
Needle Position: 3rd slot
Needle Position: 3rd slot
Mix Screw: 1/2 turn out (still running richer than Bill Gates)
I take the carbs off at least once a week and cannot get them right for the life of me.

[pamcopete]

Year: 1981/H
Location: South Carolina, elevation 700 ft.
Carbs: stock '34's
Airbox: Stock, Briggs and Stratton paper filters
Exhaust: Dunstall Replicas, 27 3/4" long
Performance Mods: 33 tooth rear sprocket, Pamco Ignition
Main Jets: 135's
Pilot Jets: Stock
Needle: Stock
Needle Position: Stock
Mixture Screws: 3 turns (Carb Guide)

Carbs off once to fix fuel T leak, again to fix the fix. No adjustments to any carb settings from stock.

Notes: Starts on first revolution, idles smoothly, low speed steady, mid range smooth, WOT smooth, no flat spots or hesitation, 60 MPG highway, 52 MPG city, plugs clean and normal color.

[pamcopete]

Year: 1978/E
Location: South Carolina, Eleveation 700 ft.
Carbs: Stock '38's
Airbox: Stock, Briggs and Stratton paper filters.
Exhaust: Classic "Kerker" 2 into 1
Performance Mods: Gerber Lid Ignition or Pamco Ignition
Main Jets: Stock
Pilot Jets: Stock
Needles: Stock
Needle Position: Stock
Mixture Screws: 2 1/4 turns (Carb Guide)
Carbs off 8 times in 12 years, mostly for routine cleaning. No adjustments to any carb settings from stock.

Notes: Starts on first revolution, idles smoothly, low speed steady, mid range smooth, WOT smooth, no flat spots or hesitation, 55 MPG highway, 47 MPG city.

[ignition]

Year: 1977D
Geographic Location and Altitude: Milwaukee, WI (634 Feet above)
Carb set: BS38
Airbox: None. K&N Pod Filters
Exhaust: Mac Header pipe with 14" welded on as straight pipes. JC Whitney 4" Baffle in end.
Performance Mods: Pamco Ignition System.
Main Jet: 132.5
Pilot Jet: 30
Needle: Stock
Needle Position: 2
Mix screw: ~2 1/8 each side
How many times you've had the carbs on and off the bike!: Several.

[10ecjed]

# Year: 1980 XS 650G
# Geographic Location and Altitude: Frederick MD about 400ft above sea level.
# Carb set: BS34
# Airbox: Stock
# Exhaust: Stock, stock header w/ mufflers, bad exhaust leaks in mufflers.
# Performance Mods:Piston's 2nd over size, heavy duty clutch springs
# Main Jet:stock
# Pilot Jet:stock
# Needle:stock
# Needle Position:stock
# Mix screw: 1 3/4 turns out.
# have had carbs off many times due to sinking floats, replaced with Mikes plastic floats, then they started sticking, repaced with new OEM brass floats, installed carb bottom end rebuild kits from Mikes.

# Notes: Runs great, clutch slipping some at high revs,I think carbs are running a bit lean. I will be readjusting soon.
I like the 58mpg

[10ecjed]

UPDATE for the 1980 XS650G
I also replaced the fuel petcock with on/off position from Mikes. This works a lot better and installed the little square fuel filter. Thaat was a pain.

[robertob]

# Year: 1975
# Geographic Location and Altitude: Los Angeles, CA approx 200 ft.
# Carb set: 1978 BS38
# Airbox: Mike's K&N knockoffs
# Exhaust: Unknown non-stock meggas, with Emgo baffles and fiberglass packing
# Performance Mods: none other than above
# Main Jet:140
# Pilot Jet: 30
# Needle: stock 78/79 (502)
# Needle Position: fourth from bottom, but it's not right. I've just moved it up one but not ridden yet
# Mix screw: 1.75 out
# How many times you've had the carbs on and off the bike!: only two or three but I did buy another set of carbs off ebay and cleaned them very, very well.

Notes:
- Midrange was almost perfect with just the baffles, but it was too loud, so I added some 'glass packing. Now midrange/high rpm is a little too rich and stutters. I moved the needle down one more notch, but haven't ridden it yet.
- Ideal might be needle up a little and down one jet size to 137.5 or something.

[mashermoto]

Year: 1981 Special
Location: Yukon, Oklahoma
Carb Set: Mikuni VM 34 Round Slides
Airbox: MikesXS pods
Exhaust: Stock headers with MikesXS shorty reverse cones
Performance Mods: MikesXS 750cc kit, WebCam 59, heads ported to clean up casting flaws and reshape the valve guide boss area, valve job, elephant foot tappets, modified crankcase breather, MikesXS high output coils.
Main Jet: 190
Pilot Jet: 22.5
Needle: 6F9
Needle Jet: P6
Needle Position: 3rd slot
Mix Screw: 1 and 1/2 turn out
Air Jet: none

I took the carbs off quite a bit to setup the pilot jet, needle and general fitting.

The slide cutaway is a 2.0, which works Ok, but would have liked to have the leaner 2.5 cutaways.

Here is an update. The bike started showing the signs of being rich during full throttle roll offs. I moved down to 175's because that was all that was available. It cured the rich condition, but plug were reading a bit lean. So now I'm running 180's. Also, mixture screw is more like 2.5 turns out.

[Bodhi]

# bike year: 81
# Altitude: Blue ridge Mtns @ about 2,000 ft
# carb: BS34's
# Airbox: Pods...K&N knock-offs
# Exhaust: Drag pipes mildly baffled
# Performance Mods: none
# Main Jet:135
# Pilot Jet:46
# Needle: XS Johns
# Needle Position:stock from manufacturer
# Mix screw: In turns out. 2.5
# How many times you've had the carbs on and off the bike!


When using the Heiden needles, more times than there is sand on the beach, when I switched over to XS John's needles, only once with some minor fine tuning.

# Notes: List anything else that you believe to be relevant about your machine!!!

Let me re-emphasize, I played with the Heiden needles for weeks using multiple combinations, none of which worked well. Johns needles worked first time out and the bike runs like a raped ape.

[browder]

Year:1972
Location:S.E. Michigan
Carb set:1979
Air box:K & N's
Exhuast: stock head pipes-Emgo trumpets
Performance Mods: Pamco ignition
Main: 135
Pilot: 30
Needle: stock
Needle position: stock
Mix Screw: 2 turns
How many times off: more times than i'll admit too

had trouble with the 72 carbs and scraped em for a set of 79's i had-- those gave me pretty much the same problems of fouling plugs no matter how i jetted--put new seals on shafts along with choke plungers re jetted twice since and all seems good so far-plugs look great--synched using dead cylinder think i can get it a little better but bike is running hard as is

[imcgyver]

Year:1981H
Geographic Location and Altitude: Littleton, Colorado 5200+ feet
Carb set: BS34
Airbox: Stock with new factory filters
Exhaust: Stock
Performance Mods: None
Main Jet: Stock
Pilot Jet: Stock
Needle: Stock
Needle Position: only 1 position, stock
Mix screw: 2 turns out.
How many times you've had the carbs on and off the bike!: 4 times for cleaning, kit, float level 22mm and new mixture screw orings, messed up new orings found putting spring , washer then oring on needle pointing up and intalling it with carb upside down I never had a problem, JB weld vacume barb back in holder no leaks now, non vacume petcock.

[skidro]

Year:1979
Geographic Location and Altitude: Silver Spring, MD 200+ feet
Carb set: BS38
Airbox: MikesXs K&N knockoff pods
Exhaust: MikesXS 2 -1 with taper tip muffler
Performance Mods: None
Main Jet: 137.5
Pilot Jet: 32.5
Needle: Stock
Needle Position: 3rd notch
Mix screw: 2 1/4 turns out.
How many times you've had the carbs on and off the bike!: 3 times for cleaning, float level 24mm,etc. Need new orings on idle mix and needle float.

The bike runs good but it will pop/hesitate coming off idle or when I decel and then hit it. All low end. It may be running a little lean and I may go up to 140 on the main. That may require dropping the needle one notch.

I have adjusted the cam chain, valves, cleaned/lubed ACU, plugs, new points but I need new coils (stock and old) and plug wires.

[xsleo]

75 XS650B
Earlville, NY about 1200 feet
bs 38 from 76 or 77 with 74 internals
K&N pods
stocks headpipes and mufflers with baffle plug knocked out
First over pistons and rings, minor cleanup of ports. higher output coil, opened the plugs to .038 gap. Power brake valve in breather hose
130 main
45 pilot
4N8 needle clip in #4 slot
Z-6 needle jet
about 1 1/2 turns out on mix screw.
Runs well, a few pops on coasting.
Carbs off, I've lost count

[xcbullet]

Year:79 SF

Geographic Location and Altitude:med. Michigan 1,000ft ?

Carb set: BS38,
Airbox: Stock W/better flowing foam from work
Exhaust: Stock,
Performance Mods: .02 over,oil cooler

Main Jet:137.5

Pilot Jet:went up to 30

Needle: stock
Needle Position:lowered needle 1/3 shim(.013inch) in 3rd

Mix screw: 2 1/4

How many times you've had the carbs on and off the bike!: plenty but just changed the pilots with out removal


Notes: Lowered one tooth on rear sprocket to 33 & like it.Used clips for shim's ,ground out center part.With the needle change had to go up on the pilots.Went up one on the mains for safety.Runs more snappy & plugs look better than the black had before.

Update after pamco E.I. , the green monster & cut out back side of air box

Main 142.5
pilot 27.5
3rd