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Carb jetting

Discussion in 'The Garage' started by dlabkeeg, Dec 29, 2009.

  1. figure8

    figure8 XS650 Guru

    The bike did run but very rough.

    A few problems now fixed. The float levels were set to 16mm so I adjusted them to 22mm. I put the rubber plugs over the pilot jet. My problem now is getting it started. Before I had it worked on I could easily kick it. I was attribiting my recent trouble getting it running to the carb issues. Since I have fixed those I still am having a hard time kicking it over. The plugs are clean, what could my mechanic done to make this so hard to start?
     
  2. As you have no datum now to measure where you carbs "are" put your mixture setting to thereabouts factory, check when kicking, you are getting a spark and also check there is a whiff of petrol, not to much though, don't want soaked plugs. If you have all the ingredients for fire - spark, air and petrol, she should kick into life. I have had similar issues on British single rebuilds and have had to resort to my friendly hill and bump it just to get it fired, then you can get a great handle on where "it's at". Alternativey, a sniff of easy start can help, however, I'm not a big fan of this method, as I am a believer engines can get hooked on the stuff and refuse to start without it!
     
  3. figure8

    figure8 XS650 Guru

    How can I check to make sure I'm getting a good spark?
     
  4. So, if you pop both plugs out ( makes it easier to kick over ) then attach your plug leads in the normal way, then secure you plugs to your engine block, making sure there is a good earth connection to the metal castings. I normally use little sprung clamps, however you may choose to use G clamps, croc clips etc.

    Once that's done, switch one in the normal way and give it a good kick. It helps if you can darken the work area as you can see the spark easier, also if you have a kick only, a friend to spot the spark also helps. You should see a nice white, white orange, or white blue spark at the tip of the plug.
     
    gggGary likes this.
  5. gabecustom

    gabecustom XS650 Enthusiast

    new bike to me.. question about my BS34's. disassembled the carbs and one of the main jets has a brass washer between the main jet and where it threads into the jet needle and the other didn't.. how important is it to have this washer/spacer or whatever it is?
     
  6. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Very important, the washer and jet hold the orifice in place. Well it should be there anyways, varnish holds well too.
     
  7. gabecustom

    gabecustom XS650 Enthusiast

    okay, thanks! I'll see if i cant come up with another one some how.. would replacing it with say a stainless or steel washer be okay? or should i stick with brass?
    one more for you, the needle jet is a snug fit, not threaded, correct? if so, should i tap it out the diaphragm or float side?
     
  8. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Yes a will fit washer should be OK. It is just a snug fit. You need to be yery careful tapping it out from the jet side towards the diaphragm side. A properly sized flat ended drift so you don't mushroom it or wreck the jet hole threads. There is also a locating pin in the carb body, don't let your drift hit that. WD40 or pb blaster will help loosen it, so will heating the area with a hair dryer.
     
  9. gabecustom

    gabecustom XS650 Enthusiast

    okay, thanks a ton! i'll get these puppies popped out and give them a shot of carb cleaner! thanks for the info Gary! its much appreciated!
     
  10. 5twins

    5twins XS650 Guru Top Contributor

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    I thread a screw into the main jet hole and tap on that instead of the jet. If the needle jet is gummed in there, you'll need to tap it most of the way out, so use a long enough screw, like an inch or inch and a half long. It's just a common metric thread size, M5 I think.
     
  11. gabecustom

    gabecustom XS650 Enthusiast

    good call, I soaked the carbs in Yamaha's Carb dip so i'm hopin they'll just pop right out.. any advice on how to get the float pins out? I've got new ones in the mail, should be here Friday, to replace the old ones, but the oil pins do not want to come out! i've never had trouble with them before in other carbs, but this is the first time these carbs have been apart in quite a wile, i can tell! ideas?
    thanks again.
     
  12. 5twins

    5twins XS650 Guru Top Contributor

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    I use a 1/16" pin punch and some GENTLE tapping. The head end of the pin is splined so they don't just slip out.
     
  13. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Be very careful, more than one of those little posts has been snapped off, support the post just below the head of hte float pin while tapping.
    I'm a home made tool nut but this works every time.

    [​IMG]
     
  14. littlebill31

    littlebill31 Smells of Raw Fuel

    I now use a c-clamp as Gary describes. However, I used to, with good results, use channel locks. I open them up enough to fit. With the bottom jaw, cover the end of the pin. With the top, place on the post just above the head. So it can come out obviously. Then a slight, quick, light pop to get it out just enough to get a hold of the head with something. You need, as Gary said, be very careful. I have not broken one, somehow. But it's only a matter of time.
    Also, try not to torque the pin. Get it out straight. They bend very easy, which can bind the floats when you reinstall them.
     
    gggGary likes this.
  15. gabecustom

    gabecustom XS650 Enthusiast

    wow! you guys have thought about everything!!!!!:thumbsup: thanks for the help! i'll keep you posted on how it goes.
     
    gggGary likes this.
  16. Would too rich a mixture lead to cracking and popping from the exhaust during deceleration? I have stock jets. I'm wondering if I need to lap the valves.
     
  17. 5twins

    5twins XS650 Guru Top Contributor

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    That's usually a sign of leaness. It usually indicates the need for a larger pilot.
     
  18. gabecustom

    gabecustom XS650 Enthusiast

    5twins is correct. if you've got pods or anything other than stock exhaust, you need to re-jet your carbs. stock jetting wont cut it. stock jetting is designed to work with stock airbox and stock exhaust, a very restrictive system. any modifications with either will cause back firing and poor performance with out re-jetting the carbs.
     
  19. uebe

    uebe XS Goober

    I thought the stock airboxes are less restrictive...................????
     
  20. weekendrider

    weekendrider Iron Horse cowboy Top Contributor

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    uebe do you always use the big paddle when you want to stir the pot? :wink2:
    Good question.
    Will it draw the same volume regardless of the filter system?
     
    gggGary likes this.

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