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ANOTHER jetting thread. I know what I'm talking about now... I think...

Discussion in 'The Garage' started by Jawknee21, Dec 13, 2011.

  1. Jawknee21

    Jawknee21 XS650 Addict

    Ok, so im going to try fixing my jetting. After a few months of 30mpg i think its time.
    Heres what i got,
    83 Sk
    Bs34s
    142.5 main
    127.5 air

    Wheres the pilot jet?
    Under that rubber plug? I had the carbs completely apart today and didnt bother looking in there...

    3 turns out on air mix screws
    1 turn out on idle screw (around 1200rpm)
    Pod filters (just cleaned and oiled not covering passages)
    Gordon scott drag pipes. Just took my baffles out.
    Pamco ignition

    I have read the whole carb guide. I plan on reading it a few more times too though. haha.

    Baffles in, plugs were black and it seemed to have decent, not good, low end but it would be around 4000 rpms at 60mph. Neutral easy to find. just Seemed slow. Terrible mileage

    baffles out, little louder, better sound, little quicker acceleration, crappy low end, i think the advance was coming early (2300rpm?), When i slowed down in 2nd to turn it stalled. Hard to find neutral.



    What else might help?
     
    Last edited: Dec 13, 2011
  2. Patches

    Patches XS650 Junkie

    Yup, the pilot is under the plug. You need to remove it and find out what size it is. Judging by your main, it may be too big.
    Sounds like you are running rich.
    Your mains seem a little big, you may want to go down to 140's and give those a try.

    How's your timing?
    Did you sync the carbs?

    Carbs generally have little effect on your ability to find neutral.
     
  3. 5twins

    5twins XS650 Guru Top Contributor

    17,657
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    Yes, read the carb guide again ..... and then again ..... and then again, lol. You're not understanding your carbs yet and how the different circuits interact. Your mains are too big and your air jets too small. Nobody really plays with air jets (although they should) because they are really a last phase, fine tuning sort of mod. You don't start there or even try them midway through a carb tune. As I said, they're a final step, a fine, fine tuning step - and only if you really know what you're doing. From your description, you're way far away from that. You don't even know for sure where your pilot jet is.

    Hopefully you haven't damaged your engine from running too rich these last few months. My buddy fried his. I gave him more credit than he deserved when I believed him telling me he did total carb rebuilds and replaced everything in there he could. When I finally had a look, I found plastic floats in '80 carbs but set to the '80 carb brass float specs. Also, totally black and gummed up needle jets. The bike ran so rich it puffed black smoke and this was with stock jetting, Mike's shorty mufflers, and UNI pods. The rich running washed the oil out of the cylinders and they scored up terribly. He needed a rebore. The simple top end for a cam chain guide ended up costing him hundreds more for oversize pistons, rings, and a bore job. All because he was carb stupid.
     
    Last edited: Dec 13, 2011
  4. Jawknee21

    Jawknee21 XS650 Addict

    Ha! im still learning. The carbs were clean inside. I didnt jet this before. I pretty much used the baffles to tune it(yea i know. dont gotta tell me). it was jetted for stock exhaust and pods. thats all. i synced carbs and did timing. If i break something i definitely learn what i did wrong. I only have the next 2 main jets up from what i have now. looks like ill be ordering from mikes soon. What should i buy? Stock jets and how many sizes up on what? Im thinking canadian needles too. Im probably going to be keeping the exhaust open. Maybe doing that washer thing instead of baffles?
     
  5. Jawknee21

    Jawknee21 XS650 Addict

    Should I buy the Heiden jet kit from mikes? Or everything separately? Needle jets? How many sizes of each jet would I need? 2 up on mains and pilot? Air jets? I'm gonna go back to stock and work from there...

    Posted via Mobile
     
  6. Jawknee21

    Jawknee21 XS650 Addict

    Whats the conversion for using main jets as air jets? Mikes says theyre the same. 85 is stock for the sk and none of the main jets on mikes are that low. I have a 127.5 air jet. Are the differences in air jets 2 1/2 also?

    Ok, just read that the Air jets are smaller diameter? My manual says stock is 85. Mikes says stock is 135. What did this guy do?! Why would he go down on air jets?
     
    Last edited: Dec 14, 2011
  7. id start at 135 mains. go back to stock air jets, provided he changed it, leave the needles alone for now. and leave the pilot alone for now. See if you can get it running good enough to drive proper.
     
  8. grizld1

    grizld1 Grumpy old man Top Contributor

    Re. stock pilot air jet: Mike's XS listing is correct (135). Buy a better manual. Right, you're running too fat. This could be caused by a number of things, and often it's more than one of them that's the source of grief. First: since stalling when coming to a stop is a common symptom of high fuel level/low float level, look up the correct setting for your floats and inspect. If you don't want to open your carbs, level your bike front-to-back and side-to-side, put a sight tube on the float bowl drain barb, open the valve, and set the petcock on "Prime." Fuel level should rise no higher than the bottom of the carb body flange that overlaps the float bowl.
     
  9. littlebill31

    littlebill31 Smells of Raw Fuel

    Did you just set the mix screws at 3 turns out or is that how they are set after doing the dead cylinder method?
     
  10. Jawknee21

    Jawknee21 XS650 Addict

    I just set it. And I have a Haynes manual. I'm still trying to figure out the dead cylinder method. I learn by seeing/doing not reading. I haven't set float height either. Still working on that too...

    Posted via Mobile
     
  11. 5twins

    5twins XS650 Guru Top Contributor

    17,657
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    You can't set or tune your carbs until you verify that the float height is correct. If it's off, it can throw the whole state of carb tune off. There's no sense even trying to tune your carbs until you can check and properly set the floats.

    I would get 2 sizes above stock for the mains (135 and 137.5) and one size up for the pilots (45). I wouldn't bother with needles for now. If you decide to in the future, I would stay away from that Heiden kit. Reports are not very good about it and many report it just plain doesn't work. If you get the Canadian needles, you must get and use the Canadian needle jets along with them. The 2 are a matched set. The Canadian needle alone will not work well with the stock needle jet.
     
  12. Jawknee21

    Jawknee21 XS650 Addict

    ha. ok. ill try no needles. other guys are doing it. i should be able to also. thanks for all the help. not gonna get any time to work on it today. tomorrow is all mine though. might do a compression test too.

    as simple as it is, this thread http://www.xs650.com/forum/showthread.php?t=9102 just helped me a lot. i learned even more. thanks guys. gonna order today maybe.Stock air jets, one up on pilots and 2 on mains. it takes mikes a week to get to me and $10 for shipping. Im impatient and broke. Not fun. Cant wait til summer...
     
  13. littlebill31

    littlebill31 Smells of Raw Fuel

    As most will agree, you have to get those carbs tuned as close to stock (depending on your bikes mods) and only then start to think about upgrades. Your bike needs to run tip top before doing other things. If you can't tune the stock stuff you will have no hope of aftermarket upgrades.

    And always do a compression test. There are several things that can make a bike run like crap, but for some reason everyone goes right for the carbs. There is an order to follow. Cam chain tensioner, valve lash, timing (if applicable), then the carbs. Poorly adjusted valves or no compression can throw a bike way off.
     
  14. Jawknee21

    Jawknee21 XS650 Addict

    Yep. Did timing and everything. It was jetted for pods and Stock exhaust. I just did the floats and put a bigger jet and it still runs like crap. Way louder and It almost wants to die. Haven't gotten to ride it yet though...

    Posted via Mobile
     
  15. you put in a bigger jet? smaller man smaller.
     
  16. littlebill31

    littlebill31 Smells of Raw Fuel

    +1on the smaller jet.
    If you are running too rich you need a smaller jet.
     
  17. Jawknee21

    Jawknee21 XS650 Addict

    I just had the carb apart to check the pilot and floats. Im waiting on jets now...

    Posted via Mobile
     
  18. Jawknee21

    Jawknee21 XS650 Addict

    This is probably why my max speed is 70?
     
  19. littlebill31

    littlebill31 Smells of Raw Fuel

    There is a lot to these carbs, but once you get to know them, they are easily tuned. You just have to do things a certain way.
    With my '81 with cut exhaust and pods I was running a 145 main and a 45 pilot. The mix screw, after doing the dead cylinder method is set at 3 turns out, stock air jet. Runs like a bat out of hell and pulls hard all the way. But it took me a while to get it right.
    If it's running too rich then you can do a minor adjustment with the mix screw, but if it's too much, then the pilot needs to come down a size, maybe 2. Opposite for a lean mixture. Once you get it idling and running ok, then take it out and do the mid range and main jet adjustment. Jumping around is not going to do it.

    The carbs work off of throttle position, not engine speed. So, idle to 1/4 is pilot circuit (pilot jet, enricher), 1/4 to 3/4 is the slides (needle jet/jet needle) and 3/4 to full throttle is the main jet.
    With an '83 you need to have those floats at 22mm +/- 1mm. If it's off, then the carbs will flood or starve.
     
  20. Jawknee21

    Jawknee21 XS650 Addict

    I did the floats yesterday 21mm with the gasket. I didn't even realize that would affect it. I'm going to have to figure out the dead cylinder method. Never done it before. I'm pretty sure I gotta go up on my pilot. Its idling bad and my idle is only 1 turn out. I thought a 145 would be way too big? I'm at about 3500ft. My plugs still look white. Would I have to redo the idle air screws every time I change the pilot?

    And I saw the spark plug someone made to ground while doing the dead cylinder. Why is the wire on the side instead of by the electrode? I just want to make sure I'm doing it right. Looks like I'll have my jets before Christmas. Thanks for your time and patience. I'm really learning a lot...

    Posted via Mobile
     

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