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:
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.
Post by detroitmuscle07 on Sept 4, 2008 13:56:48 GMT -5
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.
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.
Last Edit: May 29, 2010 8:37:42 GMT -5 by pamcopete
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.
Last Edit: Sept 29, 2008 10:13:24 GMT -5 by ignition
# 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
# 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.
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.
Last Edit: Mar 4, 2009 23:34:08 GMT -5 by mashermoto
# 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.
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
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.
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.
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
75 XS650B with 79 forks and dual disc, braided lines, disc brake on back, Pamco ignition, Pamcopete's reg/rec mods, kill switch relay, home made harness, all LED turn, brake and tail lights, tapered head bearings, bronze bushes in swing arm, soon to get shock and fork upgrades
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
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
Last Edit: Oct 29, 2009 9:27:35 GMT -5 by xcbullet
r80rt: :)This is a splendid write up, THANK YOU!!!!
Dec 26, 2015 16:54:05 GMT -5
mashermoto: What the what is this shoutbox for? Or should I shout, WHAT THE WHAT IS THIS SHOUTBOX FOR!
May 12, 2016 22:22:21 GMT -5
motormike: Good Day ...just a FYI.. Wild Cat is this Labor Day weekend. Still go'n on. A few 650's still make the scene. Various rides at different skill levels each day.. awards dinner sunday eve. BS in the park'n lot after dinner.
Aug 23, 2016 7:57:01 GMT -5
lsettle: First post in over 6 years!
Aug 28, 2016 19:45:17 GMT -5
kardon: Wow quiet here, where did they all go.
Oct 7, 2016 2:18:13 GMT -5
gggGary: XS650.com LOL
Feb 16, 2017 20:49:02 GMT -5
buell88: Anybody have any idea who built the xs650 tracker used in the Draggin Jeans Ad on Pipeburn?
May 16, 2017 16:24:09 GMT -5
joshua: The regulator/rectifier unit I got from Mikes PMA has closer hole spacing than original. Are we supposed to mill the holes to fit?
Jun 7, 2017 19:25:58 GMT -5
joshua: My bad. I found the bracket they supplied to mount the rectifier/regulator... Uh oh. How is this meant to work? Which way is it meant to mount? Looks like I have to use some spacers or something. Good instructions would be nice.
Jun 7, 2017 22:09:52 GMT -5
craig8johnson: Not sure if this is the right spot or not but oh well...
Jul 11, 2017 18:04:15 GMT -5
craig8johnson: I'm checking the charging system. I'm afraid I might have fried the last battery. With the solid state regulator (after market) what should it be charging at. The book says, I think, 15 volts. I'm hitting 17 when revved. Is that too high?
Jul 11, 2017 18:06:19 GMT -5
gggGary: Yes 17 volts is too high, about 14 volts is max, sounds like you don't have the right regulator or it's wired wrong.
Jul 13, 2017 6:54:33 GMT -5
dean: Just saying Hello, new member who is going to fix up a 79 XS650 that has seen its better days. I will definitely have lots of questions coming up.
Jun 23, 2018 16:45:32 GMT -5
tt650: Trying to breathe life into a 1980 that's been stored (indoors) for 25 yrs. Air filters are dry rotted. Have cleaned carbs but she only runs briefly on choke then stops. Need jet setting info and other ideas that might help her idle and rev.
Jul 3, 2018 19:15:19 GMT -5
trix13: Hey everyone! New to the forum and am fighting those gremlins!! New charging system, ignition switch, coil and fuse box. Resistance is higher than normal on the ignition pick up so I'm trying to find one. No such luck yet.
Aug 16, 2018 8:50:48 GMT -5
trix13: Also, even though all of my connections are clean, I cannot seem to find out why , when at higher rpms, I hit the signals and the rpms pulse with the signals...hahah. same with the brake light. I appreciate all input!!
Aug 16, 2018 8:55:08 GMT -5
bob99: how do I post a question. I am new to the forum
Jun 6, 2019 10:52:10 GMT -5
adlpc: Hello all! Been enjoying your edifying posts and discussions - and as a fan of the XS650 since my early teenage years happy that I now own a 1980 Special which I plan to turn into a vintage half faired racer. Thank you all for being here!
Oct 1, 2019 0:58:56 GMT -5
jimothyj: Hello everyone, I just joined & wish would have known about this site in 2014 when I brought my 1974 TX650A back from the grave. I have spent a good deal of $$ and alot of time on it. Just painted it and working on electrical, I will post pics soon,
Apr 10, 2021 2:14:13 GMT -5
louisvan: trix13 - I had a problem with my 1975 SX650. When I got to highway speeds, the engine lost power. The problem was in the connectors. At a certain vibration and the wind pushing on the wiring loom, the connector lost continuity. A bad crimp to the wire.
May 20, 2021 1:19:09 GMT -5