1. Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

Possibly not firing on one cylinder

Discussion in 'XJ Technical Chat' started by Josh85, Jan 26, 2019.

  1. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    Hi guys,

    I have an 81 XJ650 that I’ve been tinkering with for a few months now with varying degrees of success.

    Firstly, Its been modded with pod filters (previous owner, let’s not start on this one) it also has a dirt bike exhaust welded on and some new electrical components.

    It was idling very rough and hanging on higher revs at stop, then on a ride it only barely made it home limping (didn’t want to start and barely ran)
    When I pulled the plugs they were all very black
    so I have:

    - Rebuilt carbs (everything apart from idle enrichment circuit) including slide diaphragms and intake boots and took jets back to stock (they were 45, 128)
    - new spark plugs
    - lubed the throttle cable

    Took it for a quick run and it got significantly worse once it was hot.
    Now when I start it backfires a lot and shoots bluish flames out the exhaust along with running shit unless on about half choke (looks great but doesn’t run great)
    When I rechecked the plugs, they all look a nice grayish colour now except one which doesn’t look like it’s firing at all (checked and it still has spark and looks wet from fuel)
    Also, the exhaust coming from that cylinder is much cooler than the rest

    Can someone please guide me to the next logical step?
    Should I be checking the coils? Valve clearances? ‍

    Ps If there’s any members around the Gold Coast area with some spare time and know how, I’d be very keen to get some help with this one
     
  2. Jetfixer

    Jetfixer Well-Known Member

    Messages:
    3,173
    Likes Received:
    1,485
    Trophy Points:
    113
    Location:
    Nothern Indiana
    The cylinder that appears to not firing , unthread the plug cap fron the plug wire trim a short bit off the end, rethread the plug cap back on and put back on plug start it up and see if pipe heats up . Try this first.
     
  3. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,613
    Likes Received:
    6,703
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    The PO rejetted to suit the pods, and hopefully did it correctly.
    Stock jets are contributing to the issue, but not the reason that one cylinder isn't firing.
    I agree ith Jetfixer. Start by confirming spark on that plug.

    The plug color and need for enrichment to be on mean that she's jetted lean (because of the combination of pods and stock jets).
     
  4. Chitwood

    Chitwood Well-Known Member

    Messages:
    866
    Likes Received:
    374
    Trophy Points:
    63
    Location:
    Fort Atkinson, Wisconsin
    Checking the valve clearance isnt a bad idea at all, not likely the reason for a cylinder not firing but is often a neglected maintenance item.
     
    Franz likes this.
  5. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    Hi Jetfixer,
    Thanks for your reply. I cut off around 1-2cms and threaded the plug cap back on. No change unfortunately. It would’ve been great if that worked though!
     
  6. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    The PO put in 45/128 jets. According to https://raggedmoto.com/carburetor-jet-size-calculator/
    I need 41/124 for current setup. It was running rich before going back to factory.
    Also, I thought grey was ok, not lean. Pretty new at this so happy to be corrected though.

    Anyone had any experience with rejetting by drilling out?
    Alternatively, does anyone have a source for hitachi jets, or a jet pool?
     
  7. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    Thanks Chitwood, it’s on the list. I’ve got the shim removal tool on its way
     
  8. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,613
    Likes Received:
    6,703
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    The plug color is good, but not quite ideal. It may be contributing to the issue since the condition worsens when the engine is up to temp. You should never have any popping or a hanging idle, both of which are indicitave of a lean condition regardless of cause.
     
  9. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods
    hatachi jets are listed by the metric drill size used
    I think the drills would cost more than the jets

    source for jets www.xj4ever.com our supporting vendor
     
  10. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    Ok, thats good to know.
    The hanging idle was also present before I took jets back to stock, but the plugs were definitely carbon fouled (with 45/128’s)
    I’ve also checked throttle cable returnand it looks like it’s snapping back nicely
     
  11. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    Thanks, I’ll see if I can get a price on both options. I’ll post the outcome
     
  12. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    Just
    Just having a look at jets vs drill bits:
    New Jets will be usd29.95 each set of 4, so around $60 total.
    Drill bits are around $3 for 21 piece set including a 0.41mm (0.0160”) off eBay.
    The 1.14mm (0.45”) I need is usd$4 from grainger.com
    Just wanted to double check that is what you meant by metric sizing on hitachi jets eg #41 pilot is 0.41mm?
    Has anyone tried drilling their own jets?
     
  13. Chitwood

    Chitwood Well-Known Member

    Messages:
    866
    Likes Received:
    374
    Trophy Points:
    63
    Location:
    Fort Atkinson, Wisconsin
    The problem with drilling jets is that you cant go back when you realize you went a size or two too big. I would recommend spending the money on the jets themselves that way you can swap them around until you find what works for your set up. After which if you really wanted I'm sure you could sell any remaining jets
     
    Jetfixer likes this.
  14. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods
    you need metric drills not converted sizes from inches
     
    k-moe likes this.
  15. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    True, the PO had it running 45/118’s so I might put those back in and attempt to create laminar flow with the pods I have to try to match the jets
     
  16. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    I still need to work out why it’s not firing on one cylinder. Any suggestions?
    Replace coils?


    I’ll resistence test the spark plug wires/caps to eliminate those in the next couple of days
     
  17. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods
    swap the mating spark plug wire see if the problem follows the wire seta 1 and4 , 2 and 3.
    if not swap the spark plug.
     
  18. Josh85

    Josh85 New Member

    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Tugun, QLD
    Thanks xj550h,
    I just swapped 2 & 3 leads (4 wouldn’t reach 1) and still the second exhaust isn’t heating as much as 1,3&4.
    This is the second new plug since owning and I’ve swapped 1&2 spark plugs. The plug looks like it’s firing in 1st cylinder but I might redo that test.
    Any other suggestions?
     
  19. Jetfixer

    Jetfixer Well-Known Member

    Messages:
    3,173
    Likes Received:
    1,485
    Trophy Points:
    113
    Location:
    Nothern Indiana
    Possible PO already drilled out...ALWAYS be weary of what the PO did or did not do.
     
  20. Timbox

    Timbox Well-Known Member

    Messages:
    2,278
    Likes Received:
    748
    Trophy Points:
    113
    Location:
    Wisconsin, Tomah
    From the reading above you are saying it is not getting warm? You have pulled the plugs and visually seen the spark of all four plugs? If you have verified that you have spark on all four, then you will have to check the carb for that cylinder. Just guessing if it has spark but the exhaust pipe on that cylinder is not getting hot then there is no gas/air to burn in the cylinder?

    As for drilling out the jets, is it really worth maybe not getting them perfectly bore sized and or smooth? When I first stared my first XJ project, I pulled my carbs six times, yes SIX times, before I got them correct. I learned and now really take the time to do them right the first time, no trying to find short cuts or maybe that is good enough.

    As Jetfixer said the PO might have done some good and some bad, you will just have to check over the bike in all safety aspects to have that warm fuzzy feeling about taking it down the road.
     

Share This Page