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Carb questions from another new guy! - New (to me) 78 cs650

Discussion in 'The Garage' started by Kubes42, Jun 8, 2020.

  1. Kubes42

    Kubes42 XS650 Member

    Carbs are synced as of today! Honestly the bike is running great now. Starts on first crank. Idles very steady right at 1200 rpm. No more pops or backfire. Pulls strong all the way through the rpms. doesn't bog down or sputter. slight lag to return to idle when revving in neutral, but when riding, it doesn't feel noticeable. Maybe running a tiny bit lean as I returned it down to a more modest jetting, but im gonna give it some time so I can get a better feel for it before playing some more with jets now that im confident its ridable and not gonna die down the street every few minutes.

    I'm super happy with the progress so far, being this is my first attempt at an older bike like this!

    But now im just curious, Why can the bike run fine with the right spark plug disconnected (while trying to do the dead cylinder method after balancing carbs), but die immediately when the left is disconnected? Why can the right side not continue to run?
    (it did have the lower of the two pressures when balancing them today, but they are now spot on even)
    grizld1, Mailman and gggGary like this.
  2. gggGary

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

    you might have a dirty idle circuit or partially plugged pilot jet, a leaking or plugged choke circuit.
    Check plug wires plug caps spark plugs swap sides see if the problem follows the ignition parts. Have you done a compression test, set valves, set cam chain?
    Kubes42 and Mailman like this.
  3. Kubes42

    Kubes42 XS650 Member

    Honestly i swapped in some new iridium spark plugs and had no issues running on each cylinder individually after that so i could fine tune each fuel mixture screw. Looks like problem solved! And it seems like the bike pulls noticeably stronger now with the iridium plugs (or I finally just tuned it right... idk haha). either way it's good!

    Engine is running super smooth, could not be happier with all the help, thanks! :cheers:

    Now that it runs great, it's time to change gears and go learn about all the wiring. Bike has some LED lights that are wired up but the rear are steady on when the turn is selected (solid yellow, no flash), the brake indicator light in the gauge cluster is always on, and the flashers are not wired to the gauge cluster indicator so I cant easily see my own indicator flashing, making it easy to forget about.
    Im sure i'll have a separate thread with questions down the road about it!
    grizld1 and gggGary like this.
  4. gggGary

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

    As a precaution keep an eye on your oil level.
    grizld1 and Kubes42 like this.
  5. 5twins

    5twins XS650 Guru Top Contributor

    Your bike has a light checker to monitor the tail/brake light. It illuminates that dash light full time if one burns out. If you switch to a LED tail light bulb, the voltage draw is so low the light checker thinks it's burned out, so the dash light comes on. I put a LED tail light bulb in mine and "fixed" the dash light by simply removing it's bulb, lol.
    Kubes42 and gggGary like this.
  6. bosco659

    bosco659 XS650 Junkie XS650.com Supporter

    That’s great that you have it “dialed in” now. Are your plugs still getting sooty and are the head pipes cooler now?
  7. Kubes42

    Kubes42 XS650 Member

    Haven’t gone out for a ride longer than 15-20 min but the plugs look so much better! Not sooty at all. I’m actually thinking they are a tiny bit on the lean side but I want to get some more time riding and get a better feel before I go change anything else.

    The head pipes seem to get to run a normal temperature now. I’ve let it run for 45 min with no issue....Compared to the glowing red hot it trended towards after a 5 min idle before I starting fixing things, I think it’s good to go.

    With it being a new bike to me, I’m going to keep a close eye on it for a long time before I trust any of it!

    5twins...removing that dash light sounds like the easier way to go haha
  8. bosco659

    bosco659 XS650 Junkie XS650.com Supporter

    I too am a new 650 owner and experienced many of the same odd things that you had run into. I’m running PWK carbs and still can’t get them dialed in properly. Bike runs ok off idle but at idle it is inconsistent. New plugs will come out sooty and black after idling for several minutes. Many friends remind me that it’s a 44 year old bike and perhaps I’m expecting too much from it. Anyway, my journey continues!
    gggGary likes this.
  9. Kubes42

    Kubes42 XS650 Member

    Bosco, hopefully the guys on here helping me out have lead you to some useful info too! With no XS650 experience and just a tinyyyy bit of dirt bike time, I’m for sure no expert. I had the same thoughts about “not expecting too much from an old bike”. And not expecting much out of myself mechanically either honestly haha. But with help on here, lots of reading, and trial and error, the engine is running like its brand new, feels great! Ive fully enjoyed taking it from unable to turn over, to a smooth and surprisingly strong ride over the last month!

    Working on my first bike has been a lot more rewarding than I anticipated. I can see why people get into doing this all the time now haha

    Good luck continuing on yours! Just remember to walk away from it for a while when you get frustrated. It’s supposed to be fun after all, remember?!
    Team Junk and gggGary like this.

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